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Prevalence of Human Metapneumovirus in Central Illinois in Patients Thought to Have Respiratory Viral Infection Dr. Joan Barenfanger, Tina Mueller, Janet O’Brien, Cheryl Drake, Memorial Medical Ctr, Springfield, IL

The purpose of this study was to determine the prevalence of metapneumovirus in specimens submitted to Memorial Medical Center in Springfield, IL from patients suspected of having respiratory viral infection. Materials and Methods. This study was conducted from December 2, 2006 to March 23, 2007 on respiratory secretions which were either a) nasal washings with orders for RSV testing or b) respiratory specimens with requests for viral pathogens immunofluorescent testing. Cytospin preparations were tested by direct immunofluorescent antibody to metapneumovirus (Diagnostic Hybrids, Inc.). The great majority of the RSV testing was performed by an immunochromatographic sandwich assay (Remel X/pect RSV); alternatively, the immunofluorescent antibody (Diagnostic Hybrids, Inc.) was used. If the immunochromatographic sandwich assay were negative, backup immunofluorescent antibody to detect MPV was performed. Results. Testing for metapneumovirus was done on 391 specimens (78% nasal washes, 20% samples obtained at bronchoscopy and 2% sputa) which were submitted for RSV testing or for respiratory viral immunofluorescent testing. Just over half (206/391 or 53%) of the specimens came from children ! 4 years of age. Of the 391 specimens, metapneumovirus was positive in 11, and RSV was positive in 44. Of patients whose samples tested negative for RSV, 11/347 (3.2 %) were positive for metapneumovirus. The age distribution of patients testing positive for metapneumovirus was bi-modal, roughly split between children ! 4 years of age and adults over 40. The proportion of adults (> 20 years of age) who tested positive for metapneumovirus was 5/161 (4.5%), and this was greater than the proportion of children (! 20) who tested positive for metapneumovirus 6/230 (2.6%). Only one of the children who tested positive for metapneumovirus was hospitalized, but all of the adults were hospitalized. Generally, the adults were hospitalized because of suspected viral exacerbation of chronic obstructive lung disease. Conclusions. Of patients whose samples tested negative for RSV, 11/347 (3.2 %) were positive for metapneumovirus by direct immunofluorscent testing on cytopspun samples. During the time of this study (December 2 to March 23), the peak prevalence was in the 30 days following January 20. Metapneumovirus was seen in adults with suspected viral exacerbation of chronic obstructive pulmonary disease as well as in children aged ! 4 years. This newly discovered virus should be considered in the differential diagnosis of common respiratory viral diseases, especially in adults who actually had a higher percentage of positive cases than children did (4.5% vs. 2.6%).

Results Results. Testing for metapneumovirus was done on 391 specimens (78% nasal washes, 20% samples obtained at bronchoscopy and 2% sputa) which were submitted for RSV testing or for respiratory viral immunofluorescent testing. Just over half (206/391 or 53%) of the specimens came from children ! 4 years of age (Figure 1). Of the 391 specimens, metapneumovirus was positive in 11, and RSV was positive in 44. Of patients whose samples tested negative for RSV, 11/347 (3.2 %) were positive for metapneumovirus. Figure 2 show the characteristic staining of metapneumovirus. The age distribution of patients testing positive for metapneumovirus was bi-modal, roughly split between children ! 4 years of age and adults over 40. The age distribution of patients with specimens testing positive is shown in Figures 3 and 4. The proportion of adults (> 20 years of age) who tested positive for metapneumovirus was 5/161 (4.5%), and this was greater than the proportion of children (! 20) who tested positive for metapneumovirus 6/230 (2.6%). Only one of the children who tested positive for metapneumovirus was hospitalized, but all of the adults were hospitalized. Generally, the adults were hospitalized because of suspected viral exacerbation of chronic obstructive lung disease. Two typical cases are described (Case A and B). The distribution of metapneumovirus positive samples over time in shown in Figure 5. Metapneumovirus was detected between December 9 and March 16, but the majority of the cases occurred in the 30 days following January 20.

On examination, she had a respiratory rate of 24 breaths/minute and her temperature was 38.7 "C. Her tympanic membranes were normal but she had a croupy cough. The clinical impression was that she had an upper respiratory infection. Nasal washing for RSV was positive for metapneumovirus. She was prescribed a saline nasal spray and an antihistamine for congestion. Case B. A 46 year old woman with a history of alpha-1 anti-trypsin deficiency, emphysema and multiple other problems (including alcoholism) presented to the emergency department with worsening shortness of breath. She was unable to complete a sentence without gasping for air. She has had a cough 4 days prior to admission and a mild fever for 2 weeks with night sweats, runny nose and nasal stuffiness. Her daughter was ill with a viral illness a few days prior to this patient’s presentation. On examination, the patient had a respiratory rate of 24 breaths/minute, a pulse rate of 113/minute, and her temperature was 37.4 "C. She had bilateral crackles present but no wheezing initially; later expiratory wheezing and rhonchi were heard. She had purple discoloration of the toes bilaterally and pedal pulses were faint. Chest X-ray showed no acute infiltrates but her lungs had emphysematous changes. She was thought to have exacerbation of her chronic obstructive pulmonary disease, and she was admitted to the intensive care unit for treatment with mechanical ventilation, antibiotics, high dose steroids and bronchodilators. Nasal washing submitted for influenza testing was positive for metapneumovirus. Figure 1. Distribution of Patients Tested for Metapneumovirus by Age (Years) 200 180 160 140 120 100 80 60 40 20 0

Figure 3. Distribution of Positive Patients by Age (Years)

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Figure 5. Prevalence of Human Metapneumovirus in Central Illinois in Patients Thought to Have Respiratory Viral Infection

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Figure 4. Histogram of Age Distribution (Years) of Metapneumovirus Positive Patients

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Figure 2. Cytospin preparation of nasal wash stained by direct immunofluorescent antibody to metapneumovirus [Diagnostics Hybrid, Inc.]. (40x magnification).

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Metapneumovirus is thought to cause both upper and lower respiratory tract infections in children and adults, most closely mimicking disease produced by respiratory syncytial virus (RSV) with symptoms of cough, dyspnea, wheeze, hypoxia, fever and exacerbation of asthma. It may have a seasonal distribution, most likely peaking at the end of the winter respiratory season (January-April).

Case A. Previously in good health, a 21 month old toddler developed a low grade fever and a hoarse, barking cough 18 hours prior to her presentation to an urgent care facility. Review of systems was otherwise normal.

Number of Samples

Materials and Methods. This study was conducted from December 2, 2006 to March 23, 2007 on respiratory secretions from both inpatients and outpatients in central Illinois. Specimens were either a) nasal washings with orders for RSV testing or b) respiratory specimens with requests for viral pathogens immunofluorescent testing. Nasal washings were collected by standard techniques using 3-5 ml of nonbacteriostatic normal saline instilled into the patient’s nostrils. Cytospin preparations (made by centrifuging the samples for 5 minutes at 2000 RPM’s) were tested by direct immunofluorescent antibody to metapneumovirus (Diagnostic Hybrids, Inc.). The great majority of the RSV testing was performed by an immunochromatographic sandwich assay (Remel X/pect RSV); alternatively, the immunofluorescent antibody (Diagnostic Hybrids, Inc.) was used. If the immunochromatographic sandwich assay were negative, backup immunofluorescent antibody was performed.

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Materials and Methods

Background. Human metapneumovirus (MPV) was discovered by researchers in 2001 and has been classified as an RNA virus of the paramyxovirus group. Seroepidemiologic studies suggest that by age 5, nearly all individuals have been exposed to metapneumovirus. It is worldwide in distribution and several studies suggest that it may account for ~10% of viral respiratory infections in which the common respiratory viruses are not found. The detection of metapneumovirus has been delayed, partly at least due to its very slow replication kinetics in vitro and the facts that it does not replicate in continuous cell lines and it requires trypsin for in vitro growth.

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Number of specimens tested Metapneumovirus positive

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Summary of Results Conclusion – Of patients whose samples tested negative for RSV, 11/347 (3.2 %) were positive for metapneumovirus by direct immunofluorscent testing on cytopspun samples. During the time of this study (December 2 to March 23), the peak prevalence was in the 30 days following January 20. Metapneumovirus was seen in adults with suspected viral exacerbation of chronic obstructive pulmonary disease as well as in children aged ! 4 years. This newly discovered virus should be considered in the differential diagnosis of common respiratory viral diseases, especially in adults who actually had a higher percentage of positive cases than children did (4.5% vs. 2.6%).

Prevalance of hMPV in Central Illinois in Patients Thought to Have Respiratory Viral Infection  

http://www.dhiusa.com/upload_files/files/CVS2007_MPV_Springfield_IL_0424.pdf

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