Outbreak Science | Chapter 3: Clinical Symptomatology

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FIGURE 3.0 A physician examining the chest x-ray of a tuberculosis patient in 1958.


Clinical Symptomatology 1



Big Concepts

Selected Key Terms Here are a few essential terms used in the clinic to evaluate symptoms and signs for disease diagnosis and outbreak prevention. By the end of this chapter, you should be able to apply these terms and understand how they relate to other critical concepts.

3.1: Introduction to Clinical Symptomatology Accurate diagnosis, which requires an understanding of clinical symptomatology, saves time, resources, and lives. Clinical providers often do not know what is making patients ill when they first walk through the door, and they can’t test for every possible cause of illness. Part of being a clinical provider is asking the right questions and narrowing down all the possibilities using the framework of clinical symptomatology. While no clinical provider will be a perfect clinical symptomatologist, adherence to the basic principles of this discipline will help support pandemic prevention and containment initiatives.

Asymptomatic Clinical Symptomatology Comorbidities Congestion Diagnosis Differential Diagnosis Febrile Patient History Physical Exam Presentation Prognosis Signs Symptoms

3.2: Gathering Information Clinical providers gather information about patients and their illnesses through patient history, review of systems (ROS), and physical exams. In the patient’s history, they learn about the patient’s past, overall health, and current ailment. In the ROS, clinical providers investigate the appearance and function of the patient’s different body systems to identify symptoms of the illness. In the physical exam, the clinician looks for visible signs of an illness, such as changes in temperature and blood pressure.




3.3: Forming a Diagnosis

3.4: Communicating the Management Plan

After gathering all the information they need, the clinical provider creates a differential diagnosis, which lists all possible diseases or illnesses the patient might have. This process can be complex as many infectious diseases have non-specific or variable presentations. However, as symptoms and signs are recorded along with other critical information, the clinical provider can create a prioritized set of hypothesized diagnoses and further assess with diagnostic tests, facilitating the identification of the disease.

Particularly in the context of outbreaks, it is important for patients to follow clinical advice. Providers have the responsibility to guide patients, supporting their health as well as that of the general public. Once a management plan is defined, clinical providers must communicate this to the patient. Since illness carries discomfort beyond its symptoms, management plans should account for the psychological components of disease and be sensitively explained to patients to encourage them to follow these.

Vick’s Video Corner Watch “Vick’s Video Corner” as an entry point for this chapter.




Clinical Symptomatology

After reading this chapter, you will understand the clinical symptomatology framework and recognize common presentations of various diseases with outbreak potential. You’ll begin to develop the tools necessary to make a differential diagnosis and recognize the importance of delivering care that makes the patient feel safe, supported, and part of the care team. Finally, you’ll appreciate the vital role that clinical symptomatology plays in delivering accurate and timely diagnoses to prevent outbreaks.


n September 25th, 2014, Thomas Eric Duncan entered the Emergency Department (ED) at the Texas Health Presbyterian Hospital Dallas feeling ill. A group of clinical providers collected information from him, including the symptoms he was experiencing and his recent travels. That morning, Mr. Duncan, a 41-yearold man, presented a temperature of 100.1 ºF, and “abdominal pain, dizziness, nausea, and headache.” The primary nurse who saw him left a note in the chart that Mr. Duncan “came from Africa 9/20/14”; remarkably, this note does not appear to have influenced the care team’s decision-making.

It is now September 28th, 2014, in the ED at Texas Health Presbyterian Hospital Dallas, where you work as an Emergency Medicine doctor. During your shift, Mr. Duncan walks through the front doors. He is in rough shape but answers the care team’s questions and again indicates that he has recently been traveling in West Africa, specifically Liberia, where Ebola has been circulating. Within 15 minutes of his arrival, you recognize that Mr. Duncan is at high risk of being infected with Ebola, given his recent travel history. You quickly implement appropriate contact precautions to prevent further spread, order the indicated diagnostic tests, and contact the CDC per the hospital’s protocol, hoping that your intervention isn’t too late.

The doctors who evaluated Mr. Duncan’s condition gave him an extra strength acetaminophen and saline IV drip. They also ran a slew of tests, including blood tests and CT scans of his abdomen, pelvis, and head. Noting liver inflammation and a temperature of 103.0 ºF, the doctors diagnosed him with sinusitis and abdominal pain and sent him home with antibiotics for a presumed bacterial infection.

“Diagnosis is not the end, but the beginning of practice.” —Martin H. Fischer, German-American physician




Six schools across two states were closed for sanitization after potentially exposed students were identified. Fortunately, all of these potential contacts were unaffected or unknowingly recovered. Mr. Duncan’s death may have been prevented had the initial team that treated him on the 25th recognized his true affliction and applied the appropriate supportive care in time. In addition to its impact on Mr. Duncan, the delay in diagnosis exposed thousands of people to a highly fatal disease and could have launched an outbreak of Ebola in the US. While we will never know why exactly this took place, cases like these of potential medical racism, in which providers do not give a sufficient response to the conditions of people of color and other instances where medical communication errors occur, can leave many lives destroyed in their wake. This is why it’s even more critical that clinical providers employ efficient, unbiased, and logical reasoning when assessing all patients--for the sake of individuals like Mr. Duncan and the vast networks in which they live.

FIGURE 3.1 | A portrait of Thomas Eric Duncan. Less than a week after flying in from Liberia on September 20, 2014, Mr. Duncan visited a US ED with severe symptoms, including high fever, abdominal pain, and headache. He was immediately diagnosed with sinusitis and abdominal pain. Later, these symptoms were linked to an Ebola infection. Unfortunately, Mr. Duncan’s condition wasn’t diagnosed and treated swiftly enough to save his life. Image Credit: Wilmot Chayee / Adapted from: Merchant, Nomaan, and EMILY SCHMALL Associated Press. “Family That Hosted Ebola Patient Confined to Home.” Hendersonville Times-News, 3 Oct. 2014.

It takes another two days for the test results to come back. Diagnostic testing finds the Ebola virus in Mr. Duncan’s blood, confirming your fears. By this time, Mr. Duncan’s illness is quite advanced, and he has been moved to an intensive care unit (ICU) that has been cleared of all other patients. Sadly, six days after this second visit to the ED, Duncan develops multisystem organ failure. He dies four days later. A massive contact tracing initiative is undertaken to identify everyone who may have come into contact with Mr. Duncan during both his return trip to the US, and over the course of any of his movements between September 25th and 28th. Retroactive contact tracing follows 48 close contacts, 120 healthcare workers, and nearly 2,000 airline passengers who may have been exposed to Ebola from Mr. Duncan’s infection. 4



3.1: Introduction to Clinical Symptomatology

that the provider can observe, such as heart rate, temperature, and blood pressure, are defined as signs.

When we think of outbreak response, we often imagine cutting-edge technologies, like vaccines, genomics, or mathematical modeling. However, at its heart is something more fundamental: patient care. Our success in preventing and containing outbreaks depends on how we attend to individuals while they are acutely ill and whether we’re able to quickly and accurately determine the cause of their symptoms. An accurate diagnosis enables us not only to help the patient by swiftly initiating treatment and potentially saving their life but also to launch the necessary public health responses to protect the lives of others. Therefore, we rely first on doctors, nurses, and other clinical healthcare workers (we will refer to them here collectively as clinical providers) to conduct thorough exams, accurately assess symptoms, and, above all, ask the right questions of each patient they encounter. At that point, they can turn to scientists and public health officials for additional measures in outbreak response.

Taken together, symptoms and signs, which are often collectively described as ‘symptoms,’ can help a clinical provider develop a picture of what is affecting the patient and come up with a list of all the possible causes. The practice of clinical symptomatology refers to the process of narrowing all the potential diagnoses down to what is most likely to be affecting the patient, given their current symptoms and signs. This, and diagnostic tests that either confirm or refute the hypothesis, will deliver a diagnosis. The word diagnosis is Greek in origin and describes a “discrimination, a distinguishing, or a discerning between two [or more] possibilities.” In the medical field, the word diagnosis is used to describe the cause of the patient’s illness – suspected or confirmed. You might think of clinical symptomatology as an exercise confined to the four walls of your doctor’s office, but symptomatology is an ancient practice that takes place in many settings.

One of the foundational tools health professionals rely on when attending to a patient is the constellation of symptoms and signs that their patient demonstrates. A symptom is defined as an indication of a disease that is experienced and identified by the patient. This can be a physical or mental condition of a disease process, such as feeling itchy or feeling tired. It’s important to remember that symptoms may be subjective and can only be described by the patient; that’s why the communication of symptoms from a patient to a clinical provider is so crucial to identifying the disease. In contrast, the largely objective components of illness

Ancient Egyptians kept meticulous track of reported symptoms of various diseases, as well as the remedies provided by healers. Mesopotamians kept robust accounts of cardiovascular events, including those which characterized strokes. Incan practitioners could recognize several neurologic conditions, including epilepsy, and carry out neurosurgery with incredible precision and survival rates. In ancient Greece, Hippocrates, whom you’ve already met, maintained that “observation helps recognize the symptoms of each disease” and proposed a framework to




think about these symptoms: the four humors model, which we introduced earlier in Chapter 2: Epidemiology. He considered these the four leading drivers of disease, and his theory posited that health depends on the equilibrium between the four humors. Although the four humors framework has been disproven, clinicians today still rely heavily on the kind of observation and organization of symptoms that this classic model emphasized to assess the patient’s condition and determine probable causes of illness.

While early methods of assessing symptoms relied on these simple observations, a number of technological advances have made our methods increasingly sophisticated and accurate over time. Key landmarks include Galileo Galilei’s 1596 invention of an instrument for estimating heat called the thermoscope. The thermoscope was advanced further in 1612 when Italian inventor Santorio Santorio added a measuring scale. This device became what we now know as a thermometer. Another important development was Rene Laennec’s invention of the stethoscope in 1816.

As time progressed, so did our understanding of disease and our ability to detect it. Before modern methods came on the scene, healers in the Middle Ages could recognize the lung condition we now know as “cystic fibrosis” by recognizing the particularly salty sweat secreted by affected individuals. Parents first noticed the salty taste when leaning in to kiss their babies, earning the name of the “Salty Kiss,” which came to have a foreboding connotation because cystic fibrosis, at the time, meant a nearly-sure death.

The long, rich history of clinical diagnosis shows our human drive not just to treat but truly understand the causes of disease. Modern practitioners also demonstrate this same drive; through observation in context, clinicians are able to gather information about their patient’s current condition, compare the patient’s current state with their medical history, work to identify the cause of illness, and develop an effective treatment plan.

Infectious diseases were also clinically recognized in the ancient world, although their causative organisms were not yet identified. Hippocrates documented the malarial progression from chills to fever to sweats, as well as its classic enlargement of the spleen known as splenomegaly. He further deduced that malarial infection was associated with time spent in the Greek marshes. Ancient Romans similarly observed that infections seemed to increase near the swamps around Rome, for which they blamed the air surrounding the swamps. This observation has been immortalized, as the name malaria comes from the Latin phrase malus aria, meaning “bad air.”

The ability to correctly diagnose infectious diseases in particular is key to our prevention and control efforts for various diseases worldwide, as infectious diseases require accurate diagnosis and response in order to stop their spread. Epidemiologist Dr. Larry Brilliant once said, “Outbreaks are inevitable, but pandemics are optional.” In an outbreak setting, timely action is essential to prevent a fullblown pandemic. When health professionals rely solely on symptomatology or diagnostic methods with a long turnaround time, the appropriate responses can be greatly delayed.




In Mr. Duncan’s case, introduced at the beginning of the chapter, a lapse in clinical care may have cost him his life. The same error posed a massive containment risk, leading to the epidemiological surveillance of thousands of people. His tragic story illustrates the importance of clinical

symptomatology, which is not only central to procuring accurate, useful diagnostics but is also a vital tool for saving lives and preventing the next pandemic.

Stop to Think 1. 2.

What is the definition of clinical symptomatology, and how does it help a clinical provider? What is the difference between symptoms and signs?




3.2: Gathering Information

way, this is just a quick snapshot that helps the provider orient and initiates the conversation more efficiently.

Patient History

Patients frequently don’t state their chief complaints in a succinct manner; they may have a lot to tell and just launch into stories. For scheduled appointments, sometimes the scheduler (usually a receptionist) can help distill the patient’s concerns. Otherwise, the provider might have to carry out this synthesis themselves.

The process of arriving at a diagnosis, starts with taking a patient history, the record of a person’s overall health. With so much to consider, it can be quite challenging for a medical provider to see a new patient and quickly explain why they are ill. To develop a cohesive narrative from the patient’s story, clinicians follow a fairly standard framework to incorporate the various details the patient provides and to ensure they ask all the important questions. While each clinician might have a slightly different set of questions to gather the patient history, depending on where they were trained, where they practice, their specialty, and their individual approach, much of western medical care follows the same general framework described below. All of the information gathered while taking the patient’s history contributes towards the provider’s understanding of the patient’s presentation, which is how they appear on clinical assessment when they arrive at the hospital or clinic.

While it is important to listen to and validate the patient’s main concerns, it’s equally important to note that sometimes whatever prompted the patient to come into the clinic might not actually be their most pressing issue. Although a patient may come to see you because of an upset stomach, for example, you could figure out through additional questioning that they have a severe case of mononucleosis causing their spleen to enlarge and encroach on their stomach – a drastic result from a seemingly-unrelated origin. Therefore, while the Chief Complaint is a good starting point, providers should still keep their approach broad.

Chief Complaint History of Present Illness

The chief complaint describes in just a few words the reason that the patient came in for care. Importantly, a chief complaint does not include all the information that a provider might need to know, but rather just a quick explanation of what the patient is worried about. For example, a chief complaint might be “headache,” “severe vomiting,” or “blood in urine.” There is some divergence in thought about how many concerns can be listed in the chief complaint. For example, some would say that “difficulty breathing with a new cough” might be appropriate, while others would say that it needs to be limited to “difficulty breathing.” Either

To better understand the patient’s illness, the provider would also make sure to ask questions that help them gather information about the patient’s symptoms while taking the history of a present illness. Some starting points to do this are listed below: Onset: How and when did the symptoms first present? Was it sudden or gradual? What was the patient doing when they first noticed the symptoms?




Duration: How long have the symptoms been present – hours, weeks, days, months? Are the symptoms continually present, or do they come and go?

Social and Family History Important in most settings, social history is particularly key to understanding a case of infectious disease. In standard clinical settings, the social history might include questions about the patient’s use of alcohol, tobacco, and other recreational drugs, as well as their occupation and any recent travel. Social history for an infectious disease will also likely focus on close contacts. As such, the provider will ask if the patient has recently come into contact with anybody who was known to be ill or showed signs of illness, with particular attention toward any potential transfer of bodily fluids. For this, household contacts – those living in shared quarters – are particularly important, as they have the highest level of potential exposure. The provider may also ask about contacts to identify whomever else might be at risk of having contracted the disease from the patient. Additionally, learning about the patient’s occupation might give insight into potential exposures to disease, with agricultural workers having different exposure concerns than preschool teachers.

Location: What hurts/feels abnormal and where? Does it radiate from one area to another? Severity: How bad are the symptoms? How much distress is the patient experiencing? On a scale from 1-10, with 10 being the most severe distress imaginable, how severe is the discomfort?

Past Medical History Past medical history can give insight into the patient’s baseline experience of health, as well as the cause and presentation of their current illness. For example, uncovering a history of cystic fibrosis (the lung disease we mentioned earlier), may help point a physician toward a current Pseudomonas infection, which afflicts the lungs and is often harder to clear in cystic fibrosis patients. Conversely, learning that a patient has high blood pressure or coronary artery disease can alert the clinical provider to a higher risk of serious illness or even death from a known SARS-CoV-2 infection. In the context of outbreaks, these underlying conditions are particularly important, as they may affect who becomes ill, how severe their symptoms are, and what kind of support they might need in the medical setting. For example, people with asthma may be more likely to need airway support (e.g., supplemental oxygen or ventilator) if they become infected with a respiratory virus. As these examples demonstrate, a patient’s past history can provide both clues about the current diagnosis and a likely prognosis, the disease’s expected course, and the outcome in that individual.

The provider might also elicit information about sexual practices. These conversations should be handled in a non-judgmental, respectful, and culturally sensitive manner that is responsive to the patient’s comfort and emotional safety. This approach reaffirms the provider’s priorities of respect, support, and care for the patient. To help patients feel more relaxed, the provider may remind them that any test results will be protected and their answers will be held in confidence within the care team. Although family history of the disease may influence an individual’s susceptibility to certain pathogens, most clinical efforts during infectious




disease outbreaks will focus on the exposure and transmission of pathogens between individuals regardless of their specific family history. However, it may still be useful to know about the health conditions of people closest to the patient – including their family – to assess their vulnerability to disease or certain risk factors.

the breakdown of theophylline, leading to the accumulation of dangerous levels of theophylline, which can prove fatal. It is also important to ask about allergies, as this may provide insight into the patient’s current state or help the provider avoid worsening the situation by prescribing a treatment that could trigger an allergic reaction.

Travel History

Review of Systems and Physical Exam

In the case of a suspected infectious pathogen, the social history may focus more on recent travel and contacts. Has the patient traveled outside of the local area recently? If so, where and for how long? Different regions of the world and the US have different pathogens present in varying abundance, so it is crucial to know where the sick patient has been recently. The provider may also ask about the types of activities in which the patient participated while traveling. A zoologist studying bats in South America will likely have been exposed to different pathogens than a tourist who went to the same area and ate raw seafood at a resort. The provider should take this valuable information into account; the first care team’s failure to do so for Mr. Duncan during his initial visit to the hospital contributed to their inability to diagnose him correctly.

Many clinical providers continue to gather information about their patient’s symptoms by asking a series of questions about the patient’s presentation. This process is called review of systems (ROS) because providers systematically review the functioning of each group (or system) of organs in the body, whether or not it is the focus of the patient’s stated complaints. This process helps the provider gain insight into both additional symptoms and signs, while also developing a more comprehensive picture of the patient’s overall health. Some examples of organ systems are the gastrointestinal (GI) system, which includes organs like the stomach and large intestine that allow for digestion and elimination of food; the respiratory system, including organs like the lungs and airways that support breathing; and the neurologic system, including the brain, spinal cord, and nerves throughout your body that help you move, think, and feel. A list of signs and symptoms, organized by system, is provided below in Figure 3.2. While not comprehensive, this list is a good starting point for a larger discussion of the patient’s unique symptoms.

Medications and Allergies It is important to gather information about what medications the patient is taking; this will give providers insight into how underlying health conditions are being managed, as well as what therapeutics may already be in the patient’s body at a given time. Notably, certain drugs can react badly when paired with others. For example, an infectious disease clinical provider would check if a patient with asthma is currently taking the drug theophylline before they consider prescribing the antibiotic ciprofloxacin, as ciprofloxacin inhibits

Another crucial part of diagnosis, sometimes performed alongside the ROS, is a physical exam. The physical exam produces signs, as it is composed of what the provider observes. You’ve probably had a physical exam before, during which the provider performed actions like using 10



a thermometer to take your temperature, using a blood pressure cuff to measure your blood pressure, and using a stethoscope to listen to your heart and lungs. Afterward, they might have checked your ears with an otoscope, your reflexes with a reflex hammer, and your muscle strength by asking you to resist as they push and pull on your arms and legs. Throughout all of this, although you might not have realized it, they probably

checked your skin for any rashes and assessed your cognition and alertness by evaluating your answers to their questions.

Scan this QR code or click on this link to see (or hear) the clinical presentation of some infectious diseases.

FIGURE 3.2 | Review of systems for patient assessment. This checklist of symptoms and signs is a good reference for a provider to look at during the ROS. While no list of this sort would be entirely complete, this gives a good reminder of the different body parts to evaluate for symptoms and signs.




FIGURE 3.3 | The color of mucus and phlegm provides information about the type of infection. Typically a clear mucus is associated with a healthy body. White phlegm is associated with allergies or viral infections; yellow mucus indicates infection, and green phlegm is frequently seen in bacterial infections.

respiratory system like your nose and sinuses. Phlegm is a similar body product but is produced by the throat and lungs and tends to be thicker than mucus. White mucus and phlegm typically indicate a viral cause, such as influenza, while yellow and green mucus and phlegm point towards a bacterial origin, such as Streptococcus pneumoniae. Congestion can also have non-pathogenic causes, including exposure to pollutants and allergens. Symptoms of congestion might include trouble breathing through the nose or a feeling of fullness in the face. Signs of congestion might include seeing nasal mucus coming out of a patient’s nose or listening for the distinct congested or nasally-toned voices that often accompany this condition.

Symptoms and Signs Different medical fields will pay particular attention to different symptoms and signs, with infectious disease clinical providers having common disease presentations in mind that they look for during an exam. Below we provide a few examples of basic symptoms and signs that are frequently seen in individuals with an infectious disease.

Congestion Often referred to as a “stuffy nose,” congestion is a result of nasal inflammation, commonly observed in relatively minor infections. Congestion can often be associated with discharge like mucus, a gelatinous body fluid secreted by the mucous membranes of the




Diarrhea Diarrhea is the occurrence of loose, watery stools that are more frequent than usual. Clinically, there are three main types of diarrhea: acute watery, acute bloody, and persistent. It can also be described by its features, such as explosive diarrhea, typically indicating extreme urgency or a violent expulsion. There are a number of diseases and conditions that can cause diarrhea, including the Norwalk virus, cholera, dysentery, cytomegalovirus, and viral hepatitis. While it can be uncomfortable to talk about, the presence or absence of blood is important to assess, as bloody diarrhea is more associated with an issue in the large intestine, and can therefore narrow the differential to pathogens more associated with the large intestine, including Shiga toxin-producing E. coli (STEC), and Entamoeba infections. Beyond infectious causes, diarrhea can also be a side effect of medications or emotional distress. Symptoms would include a patient’s reports of diarrhea or the sudden need to defecate much more frequently or urgently than normal or producing a much larger volume of stool. Signs of diarrhea include observing loose or watery stools in the toilet bowl. Symptoms and signs that are associated with (but distinct from) diarrhea include abdominal cramps, nausea, and bloating.

Coughing Coughing is a body reflex that occurs when your throat or airways are irritated to clear mucus or irritants. It often occurs after an irritant enters the bronchial tubes in our lungs and causes them to constrict. The most common infectious causes of coughing are respiratory tract infections, such as the influenza virus. Interestingly, in some cases, the sound of the cough can indicate its pathogenic origin. For example, croup or a “barking” cough is caused by the parainfluenza virus, while a “whooping” cough is caused by pertussis. Coughing can also be caused by a host of other diseases and conditions, as well as by actions that severely damage the lungs and respiratory tract, such as vaping and smoking. If the patient coughs up phlegm, then they are said to have a productive cough, with which they are bringing up the thick mucus in their lungs. Symptoms would include a patient’s reports of a persistent cough or phlegm, a tickle in their throat, or trouble clearing their lungs. Signs of coughing would include watching the patient cough or produce phlegm during the appointment.




caused by a vast number of different pathogens, including E. coli, Mycobacterium tuberculosis, Ebola virus, Toxoplasma gondii, Plasmodium falciparum, and many others. Fever can be such a prominent symptom that many diseases even include it in their name, such as Lassa fever, Rocky Mountain Spotted Fever, and Rat-bite fever. Fevers can also be caused by other sources: heat exhaustion, stress, malignant tumors, as well as some medications and immunizations. Symptoms include a feeling of warmth and/or chills and sweating. The tell-tale sign of a fever is when a patient produces a higher-than-usual temperature reading with a thermometer; fevers are defined as temperatures greater than 100.4 °F / 38 °C whereas the normal body temperature on average is 98.6 °F / 37 °C.

Fatigue Fatigue is frequently described as lacking energy and motivation (physical and psychological) or as feeling very tired. Some infectious diseases that cause fatigue include malaria, tuberculosis, influenza, and mononucleosis, while some non-infectious causes include lack of sleep, medications, and excessive physical activity. Fatigue can also be caused by metabolic/ endocrine conditions, including anemia, vitamin deficiencies, medication, and sleep problems, to name a few. Symptoms of fatigue would include a patient’s reports of reduced energy levels or trouble getting through the tasks of their daily life. Signs of fatigue may include new-onset exhaustion, slow movement, or sluggishness in a patient.

Hemorrhage A severe symptom of some pathogen infections, is hemorrhage, which is characterized by bleeding after a blood vessel is damaged. The subsequent blood loss can occur inside the body (internal bleeding) or outside the body through an opening or wound (external bleeding). While the method of action is somewhat debated, pathogens are believed to damage the tissue of the blood vessels, which kicks off a severe inflammatory response. This tissue damage resulting from this inflammation causes leaks and impairs the body’s ability to form blood clots, which are aggregated clumps of blood products produced to stop bleeding. Dengue, Lassa, Ebola, Marburg, and yellow fever are all part of a notorious group of infectious diseases called viral hemorrhagic fevers that can cause life-threatening illnesses, as can a number of other pathogens. Non-pathogenic causes of hemorrhage include physical trauma, complications from drugs, and other medical interventions.

Fever Fevers are a temporary increase in core body temperature typically caused by illness, and a patient who has a fever is described as being febrile. Fevers help the body fight off pathogens that have caused the infection. The increased heat, induced by a brain structure known as the hypothalamus, makes it more difficult for these pathogens to survive. Fevers can be associated with chills and shivering, and they can be 14



Lymphadenopathy Lymphadenopathy refers to the enlargement of the lymph nodes, most frequently assessed by palpating (touching lightly with your fingertips) locations of known lymph nodes. The most common lymph nodes that doctors examine when they suspect an infection are located in your neck, also known as the cervical region, from the base of the neck to the base of the head. The lymph nodes appear swollen when your body recruits more blood and immune cells to fight off a new infection.

FIGURE 3.4 | Lymphatic traffic jam: an analogy for lymphadenopathy. Lymphadenopathy can be compared to a lymphatic traffic jam, leading to swollen and tender lymph nodes, typically around the neck, underarm, and/or groin. Swollen lymph nodes indicate that your body is recruiting more blood and immune cells to fight a new infection.

Think of lymphadenopathy as a traffic jam happening at your lymph nodes, which causes them to be swollen and tender (Figure 3.4). Lymphadenopathy is common after infection with Staphylococcus or Streptococcus bacteria, and, as you may expect, the most swollen lymph nodes tend to be closest to the site of infection. For example, the cervical lymph nodes are going to be most swollen with an upper respiratory infection, and you may feel swelling in the lymph nodes under your armpits after a vaccine is administered in your arm. Lymphadenopathy can also be due to non-infectious causes, notably cancer. Typically, cancerous lymph nodes will be painless when palpated yet very hard and will stick to surrounding tissue, while infectious disease lymph nodes will be painful when palpated yet fairly soft and can move with the skin. Symptoms may include pain or pressure with movement, particularly around the regions of the neck, armpit, or groin. Signs of lymphadenopathy include either visual or manual observation of swelling in the lymph node regions.

Muscle Aches Muscle aches are a common symptom described as a general soreness across the body, often ranging from mild to severe. Since there is muscle tissue all over our bodies, muscle pain can be felt anywhere. Muscle aches may be caused by infectious diseases such as malaria, the flu, polio, and Lyme disease, and they often present as bodily stress and tension that can escalate to pain. Other medical explanations for muscle aches include non-infectious causes: fibromyalgia, chronic fatigue syndrome, autoimmune disorders such as lupus, and certain medications. For the most part, muscle aches would be considered symptoms rather than signs, as the patient would have to tell their clinical provider about the pain.




Some symptoms and signs of infectious disease are direct manifestations of the pathogens’ effects on the body. For example, diarrhea caused by a cholera infection arises when the bacteria Vibrio cholerae permanently opens salt channels in a patient’s intestines. The salt flowing into your internal organs then pulls water into the intestines behind it, all of which eventually has to be released from your body through your rectum. Other symptoms and signs, such as fever and lymphadenopathy, are a product of your body’s natural response to pathogens and, more specifically, an attempt to clear the pathogen. These symptoms are the body’s normal responses to an abnormal problem. Most are common and crucial to a physician’s overall understanding of disease; however, it is more important to understand the reason for such symptoms instead of simply memorizing an exhaustive list of possible ones. This is because identifying and efficiently treating the root cause of a symptom (the primary illness) is the key to defeating the disease altogether, greatly increasing the patient’s chances of a swift recovery.

Rashes Rashes are abnormal lesions on the skin that are frequently hyperpigmented, with their exact hues varying with skin color, and they indicate some sort of irritation. Infectious agents that can result in a rash include Lyme disease, with its classic bull’s eye-shaped rash, and smallpox, which results in raised nodules. Non-infectious causes of rash include allergies, drug reactions, and heat. Symptoms would be a sensation of warmth, itchiness, tenderness, bumps, or any other descriptor of related discomfort around the affected area. Signs would be visual observation of a rash at the affected region.

Stop to Think 1. 2.

What are four key questions to consider when characterizing the patient’s symptoms as part of the history of the present illness? List four symptoms or signs that may guide a clinical provider to a differential diagnosis.




3.3: Forming a Diagnosis

These are some diseases that have symptoms or signs that are specific enough that they are considered essentially unique to a disease, such as a bulls-eye rash with Lyme disease or Koplik spots in the mouth with measles. These are considered pathognomonic indications, from the Greek words patho, meaning “disease” or “suffering,” and gnōmōnikos, meaning “able to judge,” diseases. Pathognomonic findings can help form a direct diagnosis in which only one disease is under serious clinical consideration.

Differential Diagnosis Understanding a patient’s constellation of symptoms and signs not only helps develop a clearer clinical picture but also reinforces the principle that the patient is and should be an active participant in their own diagnostic process. Patients are, after all, the experts of their own experience. Providers use their understanding of the common presentations of many diseases, also known as the illness script, to develop what is known as a differential diagnosis. Sometimes referred to as a “differential”, a differential diagnosis is a list of all the diseases that the provider thinks might have caused the patient’s presentation.

However, most infectious diseases have some symptoms in common; this is referred to as a non-specific presentation, which means you need to maintain a wide differential of potential diagnoses. An example of a non-specific presentation is a patient who shows up with a fever and gastrointestinal distress. While this patient could just have run-of-the-mill food poisoning, the culprit could also be a more serious pathogen, potentially one that could cause an outbreak.

Every patient who seeks medical help has an infinitely large differential until the provider begins to ask questions to narrow it down. For example, a patient reporting digestive issues with no cough might rule out respiratory illnesses, narrowing the differential to only diseases that have GI involvement. You can think of this process as a medical game of 20 questions, in which you try to guess what the other person is thinking by asking increasingly specific questions that help you narrow in on the unknown.

Conversely, one pathogen may manifest itself very differently within different people, a phenomenon referred to as variable presentation. SARS-CoV-2 is a great example of a virus that causes a variable disease presentation. Some people infected with SARS-CoV-2 are asymptomatic, meaning they don’t have any symptoms. Others experience neurological symptoms, such as loss of taste or smell. Certain individuals have severe, often fatal, respiratory issues. For almost any infectious disease, there will be some degree of variability as different individuals have different underlying genetics and biology, and comorbidities. We expand on each of these below: 17



Genetics and Biology: Our underlying genetic code affects everything – from how we look to who we are. Given that our genes account for the composition of every single cell in our bodies, including those involved in both our innate and adaptive immunity, our reaction to pathogens is no exception. Other biological differences like our age and sex can also impact our susceptibility to infectious diseases. Pathogens can have their own biological differences; the same pathogen species can have very different genomes in different strains that can cause very different diseases (e.g., the many SARS-CoV-2 lineages).

Appreciating the ability of different pathogens to present in similar ways, as well as the ability of the same pathogen to present in variable ways, is one of the first steps to becoming an effective clinical symptomatologist. It can take many years to develop the intuition necessary to form and rank a differential, and you are certainly not expected to become an expert in this particular clinical skill just from reading this textbook. Today, capable artificial intelligence (AI) is increasingly applied to make this process even more rigorous. These tools are becoming more common in hospitals and clinics. The challenges in determining a definitive diagnosis also speak to the importance of diagnostic tests, which we will discuss in Chapter 7: Diagnostic Tests.

Comorbidities: Comorbidities are chronic conditions the patient has simultaneously with the condition or disease of interest. For example, if we were treating a patient with COVID-19, it would be important to know if they also had heart disease, diabetes, or asthma, as these may affect the severity and course of their COVID-19 progression.

Clinical Discernment Now that you are familiar with common symptoms and signs in the world of infectious disease let’s take a look at the clinical picture for a number of high-priority infectious diseases. Table 3.1 presents examples of some highpriority infectious diseases, the pathogens that cause them, potential transmission routes that should be considered, the common symptoms and signs of the disease, and the other infectious or non-infectious diseases for which they might be confused (i.e., on the differential diagnosis list).

A given disease’s position or rank within the differential is dependent on a number of factors, including clinic location, the season of the year, and patient characteristics such as immunocompromised status and age. It is also important to recognize the potential impact of implicit bias – an unconscious association, belief, or attitude toward any social group – in developing a differential diagnosis and to consciously counteract that bias to reduce patient harm. Another concern is premature closure, in which a physician settles on an initial diagnosis and fails to note other likely hypotheses and general human error.

Clinical Diagnostic Testing Typically, clinical providers only order diagnostic tests after taking the patient history and creating a differential. Diagnostic tests generally don’t broaden their considerations, but rather confirm or rule out any of the diagnoses on their differential. Diagnostics and their molecular




Table 3.1: Infectious diseases and their symptomatology for clinical discernment. Disease Pathogen

Transmission Route(s)

Bubonic Plague Yersinia pestis bacteria

Spread through bite of infected Xenopsylla cheopis, a.k.a. “tropical rat flea,” or exposure to infected materials through breaks in skin

• Extremely swollen lymph nodes • Blackening, decay, and death of tissues • Can progress to shock, a rapid drop in blood pressure which is critical due to lack of oxygen distribution across the body organs.

Cholera Vibrio cholerae bacteria

Spread through eating or drinking water or food contaminated by feces of an infected patient

• • • •

Nausea Vomiting Watery diarrhea Leads to severe dehydration

E. coli, Giardia, Norovirus, Rotavirus


Cross species from bats and/or pangolins, but also spread by human-tohuman contact through respiratory droplets of infected individuals

• • • • • •

Fever/chills Sore throat and congestion Cough and shortness of breath Muscle and body aches Headache Loss of taste and smell

Adenovirus, Influenza, Rhinovirus, Parainfluenza, infection

Spread by consuming infected brain or nervous tissue containing prions from Bovine Spongiform Encephalopathy-infected cattle, or can be spread by injection

• • • • •

Depression, anxiety, and memory lapses Visual deterioration that can progress to blindness Slurred speech Incontinence and paralysis Progression to a coma and inevitable death

Cross species from bats, but also spread by human–to-human contact through blood and other bodily fluids of an infected individual

• Initially vague fever symptoms • Hemorrhage • Multiple organ dysfunction

Flu Influenza virus

Spread by human-tohuman contact through respiratory droplets of infected individuals

• • • • • • •

Fever/chills Cough Sore Throat Runny nose Muscle or body aches Headaches Fatigue (tiredness)

Lassa Fever Lassa virus

Spread through the handling of Mastomys genus rats or through items contaminated with their urine or feces; there is also potential for spread by human-to-human contact

• • • • • • • •

Fever General weakness, and malaise Headache, muscle, and chest pain Nausea, vomiting, and diarrhea Abdominal pain Multiple organ dysfunction Hemorrhage Conjuntivitis

Ebola, Marburg virus, measles. viral hepatitis

Lyme Disease Borrelia burgdorferi bacteria

Spread through the bites of infected Ixodes scapularis a.k.a. “deer tick”

• • • • •

Classic “bulls-eye” rash* Joint stiffness and arthritis Headache, fatigue and fever Late neurological symptoms Encephalopathy, facial paralysis, cognitive impairment

Eczema, fibromyalgia, ringworm, chronic fatigue syndrome or psychological disorders

Lymphatic Filariasis “Elephantiasis” Wuchereria bancrofti roundworm

Spread by mosquitos of the Culex, Anopheles, Aedes species carrying Wuchereria bancrofti a.k.a. “Roundworm”

• Most cases are asymptomatic • Thickened skin and ulcers • Massive edema caused by impaired lymphatic drainage

Milroy syndrome, Sporothrix schenckii, Streptococcal lymphadenitis

Creutzfeldt-Jakob Disease “Mad Cow Disease” prions

Ebola Virus Disease Zaire ebolavirus




Mycobacterial, streptococcal, and staphylococcal, infections, gram-negative sepsis


Crimean-Congo Hemorrhagic Fever, Lassa fever, Leptospirosis, Rickettsiosis

Adenovirus, COVID-19, Rhinovirus, RSV



Disease Pathogen

Malaria Plasmodium parasites

Marburg Hemorrhagic Fever Marburg Virus

Transmission Route(s)

Spread by infected female mosquitoes of the Anopheles species

Cross species from feces of Egyptian rousette bats; also spread through human-tohuman contact through infected material or fluids

Symptoms/Signs • • • • • • • • • • •

Cyclical Fever Chills General feeling of discomfort Headache Nausea, vomiting, and diarrhea Abdominal pain Muscle or joint pain Fatigue Rapid breathing Rapid heart rate Cough

• • • • •

Nausea, vomiting, and diarrhea Sore throat and chest pain Jaundice and pancreas inflammation Delirium Massive hemorrhage and multiple organ dysfunction


Marburg Hemorrhagic Fever, Rift Valley Fever, Typhoid fever, Zika

Ebola, Lassa, malaria, typhoid

Measles Morbillivirus

Spread by human-tohuman contact and aerosols, with no known reservoir

• Fever • Conjunctivitis • Koplik’s spots, “measles rash”

Rift Valley Fever Rift Valley Fever Virus

Spread through contact with infected livestock or infected mosquitos

• Fever • Weakness and back pain • Dizziness

Smallpox Variola vera virus

Spread by human-tohuman contact or direct contact with infected fluids or objects

• Acute onset of a fever of 101 ºF or higher • Subsequent rash of firm, deep seated vesicles and papules

Streptococcal pharyngitis (aka Strep Throat) group A streptococcus bacteria

Spread by human-tohuman direct contact, commonly through respiratory droplets also other body secretions including saliva, mucus or phlegm.

Tuberculosis Mycobacterium tuberculosis bacteria

Spread by human-tohuman contact through respiratory droplets.

• Severe long-standing cough that produces phlegm • Weight loss • Night sweats • Lung damage visible on imaging (e.g., infiltrates in lung on x-ray)

Blastomycosis, lung cancer, Sarcoidosis

Typhoid Fever Salmonella Typhi bacteria

Spread by the consumption of water contaminated by the feces of individuals infected with the disease.

• • • • • •

Weakness Stomach pain Headache Diarrhea or constipation Cough Loss of appetite

Cholera, Dengue, Malaria

Zika Zika virus

Spread zoonotically by Aedes mosquito bites or from human-to-human contact via mother-to-baby or sexual transmission.

• • • • •

Fever Rash Headache, joint, and muscle pain Conjunctivitis Encephalopathy in babies born from Zika

• • • • •

Fever Headache and body aches Painful swallowing Nausea or vomiting Red and swollen tonsils, with white patches or streaks of pus • Tiny red spots on back of the roof of the mouth • Swollen, tender lymph nodes in your neck


Dengue, Lassa, Parvovirus, Rubella

Leptospirosis, Malaria, Rickettsiosis

Chickenpox, monkeypox, syphilis, Rocky Mountain spotted fever

Respiratory viruses (parainfluenza, rhinovirus, coxsackievirus, adenovirus, etc.), Candida, oral Chlamydia

Dengue, leptospirosis, Malaria, rickettsiosis



and biological bases will be discussed more fully in Chapter 7: Diagnostic Tests. For now, we will focus on the deployment of diagnostics in a clinical setting, with particular attention to efficiency and resource allocation.

So let’s think about what the “horses” might be in this situation. We know that this patient has had international contacts lately, but she isn’t sure from which regions they originated; thus, we can’t completely rule out diseases that are more common outside of the US (including extreme diseases like Lassa fever, Ebola, and dengue fever). However, we can assume that she is at lower risk of having contracted these illnesses than if she had traveled to those regions herself, and there isn’t an active outbreak at the time. Furthermore, you know that it’s February—the peak of flu season. This makes influenza a likely “horse.” Other common pathogens circulating at this time of year include RSV or common coronaviruses.

Imagine that a patient comes into your US-based clinic in early February 2017. She has a low fever, a severe headache, and some muscle aches. You know from her patient history that she attended a work conference recently; she knows that individuals from around the world attended, but she isn’t sure where exactly everybody came from. For which illnesses would you want to test this patient? Perhaps given how we’ve primed you so far, you will want to test this patient for Ebola; after all, these symptoms, while not a perfect fit, do show up in the illness script for Ebola, and that would be a fairly important diagnosis to miss. However, given that Ebola is extremely rare and there is no known active outbreak of Ebola in 2017, your colleagues in the clinic might describe you as “hearing hoofsteps and thinking ‘zebras’”—in other words, you might be right, but the culprit is much more likely to be horses, i.e., a more conventional pathogen.

It looks like your most likely diagnosis, given the patient history and presentation, is seasonal influenza. A positive rapid influenza test would confirm your diagnosis, while a negative test would prompt you to further probe other possibilities, which you would rule out before pursuing other horses like RSV or strep throat, and then finally the “zebras” like Ebola.

Stop to Think 1. 2. 3. 4.

What is the term that describes the rare occurrence when a patient exhibits signs or symptoms that are specific to a disease, such as a bulls-eye rash with Lyme disease? What are two factors that may result in variable presentation of a pathogen in patients? According to the information provided in Table 3.1, what are the common symptoms that both Marburg Hemorrhagic Fever and Lassa fever demonstrate? Viral hemorrhagic fevers are life-threatening diseases, and when not diagnosed in a timely manner, the outcome can be devastating. With time being of the essence, what may be a way to determine if a patient has contracted Marburg or Lassa?




3.4: Communicating the Management Plan In the setting of infectious diseases, clinicians have the responsibility to provide guidance that will support the health of the patient they are advising, as well as the general public. As such, they should help the patient understand the illness that is currently ailing them, how to manage their symptoms, and how to avoid spreading the disease to others. These pieces of information are collectively referred to as the management plan. FIGURE 3.5 | Communicating the management plan is a clinical provider’s responsibility. The teach-back method is a way in which providers can ensure patients understand the management plan for their diagnosis through inquiry.

Clinical management looks different for different diseases. For example, if a pathogen is spread through respiratory droplets, as is the case with COVID-19, the infected person may be advised to isolate and wear a mask when sharing a space with others (e.g., in the hospital or at home). However, if the disease is only spread through the transfer of bodily fluids, as is the case with HIV, it will be safe for the patient to engage in most daily life activities, with additional protective measures in place for high-risk activities where fluids might be shared, like sexual contact.

management plan. One method to help improve the patient’s understanding is the teach-back method, by which the provider asks the patient at the end of the encounter to explain the management plan as if the provider were hearing it for the first time. Methods used in this technique include asking the patient to show how many pills they will take at various times of the day, or having them identify activities that are safe and those that are not (Figure 3.5).

Helping patients fully understand their diagnosis and management plan is key to both their and the public’s health. The management plan, however, may not be as straightforward as it seems. In fact, only an estimated 25% of Americans actually take their medications as prescribed. This can be due to a number of social factors, including trust in the clinical care system or government, comfort with the dominant language, education, and religious beliefs. You’ll learn more about these social drivers in Chapter 10: Social Determinants of Health.

Psychological Impact of Diagnosis Receiving a diagnosis can have both positive and negative impacts on the patient’s well-being. On the one hand, patients may be relieved to finally know what is causing their symptoms. Having a clearer understanding of what is going on can improve the efficacy of a treatment plan, which also has positive impacts on the patient’s outcomes. Conversely, patients may feel a sense of dread if the

By the end of the appointment, it is crucial that the patient understands the diagnosis and 22



natural progression of their condition is unfavorable. Particularly in the setting of infectious disease, they may experience stigma – an external or self-imposed feeling of disgrace or other negative attitudes towards a particular circumstance. They may experience shame, anger around their diagnosis, or fear of spreading it to their loved ones. Stigma and shame in particular can be especially pronounced for infections that are frequently, but not always, associated with sexual contact. Providers and future-providers, like you, perhaps, should understand this potential for stigmatization and shame and remember that interviews about high-risk practices, as well as the delivery of the diagnosis, should be done in a way that is both cognizant of and responsive to these social factors. Good providers will recognize that illness carries discomfort beyond its symptoms and will help the patient to navigate their new circumstances.

received, many people felt that there was no incentive to get diagnosed with HIV and even feared getting tested. Importantly, having an effective, relatively accessible treatment for a disease can change its public perception, as well as people’s willingness to be tested for it. Such a shift occurred amid the ongoing HIV epidemic after the development of antiretroviral therapies (ARTs), which motivated many communities to get diagnosed in the hopes of receiving life-saving treatment. It should also be noted that the lack of a diagnosis can also negatively impact a person’s well-being. This is particularly true when symptoms are gradual and subtle, but with harmful long-term effects, and in the worst cases, are dismissed by clinical providers. This dismissal is all too common in the medical field, and it is often disproportionately deployed when treating marginalized populations. Lyme disease, for example, is sometimes accompanied by symptoms and signs normally associated with schizophrenia and bipolar disorder, so it is frequently misdiagnosed as having a psychological basis. Being turned away without an appropriate response to or management of their infections not only fails to help the patients in the moment, but may also discourage them from seeking care in the future.

A prime example of the psychological toll of diagnosis occurred during the early days of the HIV epidemic, the mental burden of which continues to this day. In the 1980s, when we were working to understand HIV as the cause of AIDS, researchers developed a diagnostic to test whether or not people were infected with HIV. The problem was that while the testing was accurate and effective, there was still no therapy for treating HIV/AIDS at the time. Coupling this with the discrimination and mistreatment that affected communities often

Stop to Think 1. 2.

What is the teach-back method, and how does it help the patient? Name two ways that stigma can affect the spread of a pathogen.




Stop to Think Answers 3.1: Introduction to Clinical Symptomatology

3.3: Forming a Diagnosis 1. This is known as a pathognomonic indication.

1. The grouping and identification of diseases based on the significance of symptoms. They help the physician to assess the state of the patient, provide a diagnosis and come up with an action plan.

2. Biology/genetics and comorbidities both affect the illness presentation. 3. These diseases share the indications of nausea, vomiting, diarrhea, abdominal pain, chest pain.

2. Signs are objective while symptoms are subjective. Signs are the objective components of illness that the provider can observe, including heart rate and blood pressure, among many others and symptoms are the subjective components of illness that only the patient has insight into, such as feeling itchy or tired.

4. Determination could be made by diagnostic testing to confirm or rule-out one or the other.

3.4: Communicating a Management Plan 1. The teach-back method aims to inform the patient about the management plan. The provider asks questions to the patient about it. The teach-back method helps the patient to better understand the diagnosis and management plan and in this way the provider ensures the communication has been successfully passed.

3.2: Gathering Information 1. The four questions are: a. Onset b. Duration c. Location d. Severity 2. Answers may vary, but could include: a. Congestion b. Coughing c. Diarrhea d. Fatigue e. Fever f. Hemorrhage g. Lymphadenopathy h. Muscle aches i. Rashes

2. Answers may vary, but could include: a. Fear of diagnosis b. Refusal to get tested c. Reduced likelihood of receiving treatment d. Increased spread of the disease e. Loss of friends and family





Direct Diagnosis: A diagnosis that is certain or confirmed by the provider, perhaps supported by lab testing or by a pathognomonic symptom.

Asymptomatic: No demonstration of any signs or symptoms, despite being infected with a disease.

Fatigue: Frequently described as the lack of energy and motivation (physical and psychological) or feeling very tired.

Chief Complaint: a patient’s own words describing the main reason for their visit to the hospital.

Febrile: The status of having a fever; can be associated with chills and shivering.

Clinical Symptomatology: The grouping and identification of diseases based on the presenting symptoms.

Fevers: Temporary increase in core body temperature typically caused by illness. Gastrointestinal (GI) System: Body system of organs involved in digestion and fecal elimination.

Comorbidities: Conditions that the patient has simultaneously with the condition or disease of interest.

Hemorrhage: Excessive bleeding from ruptured blood vessels, which can be caused by some infectious diseases.

Congestion: The result of nasal inflammation and may involve discharge, commonly observed in relatively minor infections; commonly known as a “stuffy nose”.

Illness Script: The way a given disease tends to present which providers use to make a differential diagnosis (i.e., sneezing, coughing, chills, a fever, and loss of taste and smell for COVID-19).

Diagnosis: The cause (either suspected or confirmed) of the patient’s illness; comes from the Greek word diagnōsis, specifically meaning a “discrimination, a distinguishing, or a discerning between two [or more] possibilities.

Implicit Bias: An unconscious association, belief, or attitude toward any social group, that can impact care, such as falsely guiding a developing differential diagnosis.

Diarrhea: The occurrence of loose, watery stools that are more frequent and/or urgent than usual; there are three main clinical types: acute watery, acute bloody, and persistent.

Lymphadenopathy: Swelling of the lymph nodes due to the recruitment of additional blood and immune cells; most frequently assessed by palpating locations of known lymph nodes.

Differential Diagnosis: A list of all the possible diagnoses the provider is considering for the patient based on their presentation, signs, and symptoms; sometimes shortened to just “differential.”

Mucus: A gelatinous body fluid secreted by the mucous membranes of the respiratory system like your nose and sinuses.




Productive Cough: Coughing that produces phlegm.

Muscle Aches: A common symptom described as a general soreness across the body, often ranging from mild to severe.

Prognosis: The course a disease is expected to take.

Neurologic System: Body system including the brain, spinal cord, and nerves that support thinking, movement, and behavior.

Rashes: Abnormal lesions on the skin that are frequently erythematous (red) and indicate some sort of irritation.

Non-Specific Presentation: Signs and symptoms that are shared across many diseases, such as fever, coughing, sneezing, and more.

Respiratory System: Body system involved with breathing, including lungs and airways. Review of Systems (ROS): Clinical providers observe the patient’s health one organ system at a time to assess how the illness is showing up in the body.

Palpating: Touching lightly with your fingertips. Pathognomonic Indications: Signs or symptoms that are specific to a particular disease (i.e. a bulls-eye rash for Lyme disease).

Signs: The components of illness that the provider can observe, including heart rate and blood pressure, among many others.

Patient History: The process of eliciting additional information from the patient to learn more about their signs and symptoms, the course of their illness, their past medical history including the medications they take and their allergies, as well as their family and social history.

Stigma: A feeling of disgrace or other negative attitudes to the circumstances, either internally or from others; sexually transmitted infections are typically very stigmatized. Symptoms: Indication of disease that is subjective and can only be described by the patient (i.e., feeling itchy or tired).

Phlegm: a thick secretion from the throat and lungs that can very in color depending on state of health.

Teach-Back Method: When the provider asks the patient to explain their diagnosis management plan back at the end of the visit, in order to confirm the patient correctly understands.

Physical Exam: The portion of the doctor’s visit where the provider externally assesses and reviews the patient’s physical presentation, symptoms, and signs, including taking the patient’s temperature, and blood pressure, and using a stethoscope to listen to heart and lungs.

Variable Presentation: The capacity of one disease to manifest differently amongst different individuals. For example, some people infected with SARS-CoV-2 are asymptomatic, while others are severely ill.

Presentation: A combination of the condition the patient is in when they show up to the clinic, and the information that they share with their provider. Taken together, these can help develop a picture of what is affecting the patient. 26

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