2009 pandemic influenza A (H1N1): pathology and pathogenesis of 100 fatal cases in the United States.
In the spring of 2009, a novel influenza A (H1N1) virus emerged in North America and spread worldwide to cause the first influenza pandemic since 1968. During the first 4 months, over 500 deaths in the United States had been associated with confirmed 2009 pandemic influenza A (H1N1) [2009 H1N1] virus infection. Pathological evaluation of respiratory specimens from initial influenza-associated deaths suggested marked differences in viral tropism and tissue damage compared with seasonal influenza and prompted further investigation. Available autopsy tissue samples were obtained from 100 US deaths with laboratory-confirmed 2009 H1N1 virus infection. Demographic and clinical data of these case-patients were collected, and the tissues were evaluated by multiple laboratory methods, including histopathological evaluation, special stains, molecular and immunohistochemical assays, viral culture, and electron microscopy. The most prominent histopathological feature observed was diffuse alveolar damage in the lung in all case-patients examined. Alveolar lining cells, including type I and type II pneumocytes, were the primary infected cells. Bacterial co-infections were identified in >25% of the case-patients. Viral pneumonia and immunolocalization of viral antigen in association with diffuse alveolar damage are prominent features of infection with 2009 pandemic influenza A (H1N1) virus. Underlying medical conditions and bacterial co-infections contributed to the fatal outcome of this infection. More studies are needed to understand the multifactorial pathogenesis of this infection.
Infectious Diseases Pathology Branch, Centers for Disease Control and Prevention, 1600 Clifton Road, MS G-32, Atlanta, GA 30333, USA. wbs9@cdc.gov
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Dianna M
DM
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Amy M
AM
Denison
Marlene
M
Deleon-Carnes
Patricia
P
Adem
Julu
J
Bhatnagar
John
J
Sumner
Lindy
L
Liu
Mitesh
M
Patel
Brigid
B
Batten
Patricia
P
Greer
Tara
T
Jones
Chalanda
C
Smith
Jeanine
J
Bartlett
Jeltley
J
Montague
Elizabeth
E
White
Dominique
D
Rollin
Rongbao
R
Gao
Cynthia
C
Seales
Heather
H
Jost
Maureen
M
Metcalfe
Cynthia S
CS
Goldsmith
Charles
C
Humphrey
Ann
A
Schmitz
Clifton
C
Drew
Christopher
C
Paddock
Timothy M
TM
Uyeki
Sherif R
SR
Zaki
D000293:Adolescent; D000328:Adult; D001344:Autopsy; D002648:Child; D002675:Child, Preschool; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics / Q000472:pathogenicity*; D007251:Influenza, Human / Q000453:epidemiology* / Q000401:mortality* / Q000473:pathology / Q000821:virology*; D008168:Lung / Q000473:pathology / Q000821:virology; D008297:Male; D008875:Middle Aged; D058873:Pandemics; D014481:United States / Q000453:epidemiology; D055815:Young Adult