Pulmonary Pathologic Findings of Fatal 2009 Pandemic Influenza A/H1N1 Viral Infections

Abstract

Context In March 2009, a novel swine-origin influenza A/H1N1 virus was identified. After global spread, the World Health Organization in June declared the first influenza pandemic in 41 years. Objective To describe the clinicopathologic characteristics of 34 people who died following confirmed A/H1N1 infection with emphasis on the pulmonary pathology findings. Design We reviewed medical records, autopsy reports, microbiologic studies, and microscopic slides of 34 people who died between May 15 and July 9, 2009, and were investigated either by the New York City Office of Chief Medical Examiner (32 deaths) or through the consultation service of a coauthor (2 deaths). Results Most of the 34 decedents (62%) were between 25 and 49 years old (median, 41.5 years). Tracheitis, bronchiolitis, and diffuse alveolar damage were noted in most cases. Influenza viral antigen was observed most commonly in the epithelium of the tracheobronchial tree but also in alveolar epithelial cells and macrophages. Most cases were reverse transcription–polymerase chain reaction positive for influenza. Histologic and microbiologic autopsy evidence of bacterial pneumonia was detected in 55% of cases. Underlying medical conditions including cardiorespiratory diseases and immunosuppression were present in 91% of cases. Obesity (body mass index, >30) was noted in 72% of adult and adolescent cases. Conclusions The pulmonary pathologic findings in fatal disease caused by the novel pandemic influenza virus are similar to findings identified in past pandemics. Superimposed bacterial infections of the respiratory tract were common. Preexisting obesity, cardiorespiratory diseases, and other comorbidities also were prominent findings among the decedents.

Validation of Normal Human Bronchial Epithelial Cells as a Model for Influenza A Infections in Human Distal Trachea

“…Unstained, positively charged slides of human tracheal tissue from a fatal 2009 pandemic influenza case, lacking secondary bacterial infection, as discussed in Gill et al (2010) was confirmed positive by influenza A viral antigen immunohistochemistry. Similarly screened, normal, uninfected tracheal tissue samples sourced from NCI Laboratory of Pathology were used as uninfected controls.…”

“…Both donors were reported to have no pulmonary complications and the respiratory tissues were within normal limits with histopathology. This study also used formalin-fixed, paraffin-embedded (FFPE) autopsy tissues, as described by Gill et al (2010). Finally, additional anonymous normal human tissue sections used for immunohistochemistry controls were also obtained from the NCI Laboratory of Pathology.…”

Persistent Bacterial Coinfection of a COVID-19 Patient Caused by a Genetically Adapted Pseudomonas aeruginosa Chronic Colonizer

“…Bacterial coinfection was one of the major causes of death in the influenza pandemics last century (Hers et al, 1958;Bisno et al, 1971;Brundage and Shanks, 2008;Gill et al, 2010;Cilloniz et al, 2012). About 30% of cases was found to have bacterial coinfection in the 2009 H1N1 influenza pandemic even with antibiotic treatment (Gill et al, 2010;Hanada et al, 2018). Bacteria coinfecting with SARS-CoV-2 have also been reported by several retrospective studies based on cases from different geographical regions (Hughes et al, 2020;Lansbury et al, 2020;Rawson et al, 2020;Vaughn et al, 2020;Zhu et al, 2020).…”

“…Such viral lung infection weakens host immunity and alters the composition and functions of respiratory microbiota, predisposing hosts to bacterial coinfections (Hanada et al, 2018). Bacterial coinfection was one of the major causes of death in the influenza pandemics last century (Hers et al, 1958;Bisno et al, 1971;Brundage and Shanks, 2008;Gill et al, 2010;Cilloniz et al, 2012). About 30% of cases was found to have bacterial coinfection in the 2009 H1N1 influenza pandemic even with antibiotic treatment (Gill et al, 2010;Hanada et al, 2018).…”

Comparative Pathology of Select Agent Influenza A Virus Infections

“…154 This corresponds with the few in vivo descriptions of the target cells of human influenza virus in fatal pneumonia: Virus antigen expression is seen in alveolar epithelial cells, alveolar macrophages, and interstitial macrophages. 41,50,87,93…”