Comparison of Autopsy Findings of 2009 Pandemic Influenza A (H1N1) with Seasonal Influenza in Four Pediatric Patients
B Xu, JJ Woytash, D Vertes. State University of New York at Buffalo, Buffalo, NY; Erie County Medical Examiner's Office, Buffalo, NY
Background: The swine-origin influenza A (H1N1) virus that emerged in humans in early 2009 has reached pandemic proportions and cause over 120 pediatric deaths nationwide. Studies in animal models have shown that the 2009 H1N1 influenza virus is more pathogenic than seasonal A virus, with more extensive virus replication and shedding occurring the respiratory tract.
Design: We report four cases of influenza A-associated deaths (two pandemic and two seasonal) in persons less than fifteen years of age who had no underlying health issues. Autopsy finding on isolation of virus from various tissue specimen, cocurrent bacterial infection and pathological changes of the respiratory tract were compared between swine-oringin influenza A H1N1 and seasonal influenza infected patients.
Results: The swine-origin influenza A-subtype H1N1 was isolated from post-mortem throat swabs, lung and brain tissue and was confirmed by real time RT-PCR in two cases. Isolates from throat swabs in two other cases were positive for seasonal influenza A virus H1N1 (non-swine) and H3N2, respectively. Evidence of concurrent bacterial infection, S. aureus (MRSA), was found in lung and blood specimens in both swine-origin influenza A H1N1 patients. H. influenzae bacillus was identified from the throat culture in one of two seasonal flu cases. Examination of the respiratory tract revealed marked hemorrhagic and necrotic changes of upper airway mucosa and hemorrhagic pleural fluid in swine-origin H1N1 patients. Whereas pathology evaluation of postmortem lung specimens showed non-specific edema and congestion in seasonal flu cases, diffuse alveolar damage with prominent hyaline membrane and type II pneumocyte proliferation, hemorrhagic necrosis of bronchiolar walls and neutrophilic infiltration were evident in the lungs of swine-origin H1N1 infected patients.
Conclusions: Our study suggests that bacterial superinfection in lungs and acute respiratory distress syndrome can play a pivotal role in fatal swine-origin influenza A (H1N1) cases.
Monday, March 22, 2010 9:30 AM
Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 9, Monday Morning