Learning about a Virus

BY KATE SAGE, D.O.

Before starting with viruses, and what they are, and how they infect people, it’s worth taking a step back to discuss the di erent types of organisms that live on this planet.  e main ones that infect people are bacteria, fungus and viruses.

Bacteria Bacteria are tiny one celled organisms that live everywhere and on everything. For example, there are up to 50,000 di erent types of bacteria that live in soil. Not all bacteria harm or infect humans. Some are helpful, like the bacteria that live in our gut to help us digest. Bacteria usually have DNA like humans do, and can reproduce on their own.  ere are types of bacteria that live in our mouth, noses, gut, on our skin, and everywhere in between. Sometimes the bacteria that live on or in human bodies can become “opportunistic” and cause an infection after living peacefully for years. Staphylococcus, or “Staph” is a prime example of this. If tested with a swab, every single person would grow some type of Staph in a petri dish. But in the right circumstances, for example in a cut or a wound, that same Staph can cause an infection. Antibiotics can kill bacteria. However, bacteria can mutate, and some strains of bacteria are now antibiotic resistant. Staphylococcus is again a good example of this, and MRSA is a strain of Staph that is resistant to many types of antibiotics. Some commonly known bacterial infections include pneumonia, tetanus, meningitis, and whooping cough.

Fungus A fungus is a species that is made from a spore.  is includes yeast, mold, and mushrooms. It’s able to reproduce on its own. Again, fungus lives everywhere, including on the human body. It doesn’t necessarily cause harm, but it can. Some common examples of fungus are Athletes Foot or vaginal “yeast infections.”  ere are some that are more dangerous, including a few that can be inhaled and cause lung disease.

Virus Viruses are much smaller.  ey’re not considered living because they need a host to survive.  ey can’t reproduce on their own.  ey’re not made of cells, and basically are just little packages of DNA/RNA that attack living cells and commandeer them to reproduce and make more virus cells. Human immune systems can  ght a virus by creating antibodies to the virus. Viruses can mutate though, so when the viral DNA/RNA changes, they can re-infect a host. Some common examples of viruses are in uenza (‘the  u”), the common cold (e.g., a rhinovirus), and some of the stomach illnesses that cause vomiting and diarrhea (e.g., a norovirus). Antibiotics don’t work for viruses. However, there are some anti-viral medications that can slow the spread of the virus in the body, and make the illness last a shorter amount of time or be less severe. Tami u is an example of this for the  u. It’s not an antibiotic and it does not kill the  u virus. It does stop the  u virus from mutating in the human body and therefore slows it down.

Viruses are hard to “kill” since they’re not alive. Washing hands and surfaces will remove the virus from those areas and slow the spread.  ere are vaccines for some viruses, like the  u. Basically the vaccine injects a small sequence of the viral DNA/RNA into the person, and the human immune system can make antibodies.  at way, when the human encounters the virus in real life, they already have antibodies. However, since viruses can mutate, vaccines aren’t always 100% e ective. Other viruses that have vaccines are mumps, measles, and polio.

 e coronavirus has been known to scientists for a long time. It’s called a coronavirus because the shape of the virus looks like a little globe with spikes coming out the top like a crown, hence the name “corona”, which means “crown.”  ere are lots of di erent kinds of coronaviruses which are unique because of the DNA/RNA inside them.  e shape of all of them is the same though, and that is why they all fall into the family of coronavirus. Some types of coronaviruses cause respiratory symptoms like a common cold. Many types of coronaviruses are known to infect animals, but not necessarily humans. Some coronaviruses jump from species to species.  ere have been coronavirus outbreaks before, most notably the SARS outbreak in Asia in 2002.  e current coronavirus is called COVID-19. As of now, there is not a vaccine, but scientists are working on it. Part of the hold-up is testing it on enough people to make sure it’s e ective, but not dangerous. Some people that are infected with COVID-19 are also getting infected with a bacterial “opportunistic” infection like pneumonia. In that case, an antibiotic may be used to treat the pneumonia, but it’s not really treating the COVID-19 virus itself.

COVID-19 Test  e test that is probably most familiar is the swab that is inserted into the nose.  is is the test for an active COVID-19 infection. A person may not have symptoms, but may still be harboring the virus.  e test actually looks for the virus itself, or particles from the virus, which are captured on the swab. If this test is positive, it means that the person is currently  ghting a COVID-19 infection, whether the person is symptomatic or not.

Antibody Test  e antibody test is di erent.  is is a test to see whether your body has made antibodies to COVID-19.  is is a blood test.  ere are several on the market right now, with varying degrees of accuracy. Having a positive antibody test means that your body has been exposed to COVID-19 and your immune system has started preparing antibodies. You do not necessarily have COVID -19 currently if you have a positive antibody test.  ere are two types of antibodies that are usually tested for (and  ve kinds of antibodies total in humans, for those interested in immunology). IgM antibodies happen relatively quickly. Your body starts making these as soon as your body recognizes an infection. If an IgM test is positive, a person likely has been exposed or had COVID-19 recently. IgG antibodies typically happen a bit later, usually seven to ten days after the body recognizes an infection. IgG antibodies may prevent future infection from COVID-19, but no one knows for sure yet. If an antibody test is performed too soon, like when someone  rst gets the virus, IgM and IgG may still be negative on testing. If someone gets a test in the mid part of the virus, the IgM antibody may be down, but the IgG may not be detectable yet. A person may end up having antibodies eventually in either of those cases, but the antibody test may still show up as negative. A falsely positive antibody test can also a bad thing: if someone tests positive for antibodies, but they really are negative, that person would be a false sense of con dence that he or she cannot get infected.

Dr. Katherine Sage is an Orthopaedic surgeon. She likes to write about medicine, science, and women’s place in the universe.