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.
Shieh
Wun-Ju
WJ
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
Deleon-Carnes
Marlene
M
Adem
Patricia
P
Bhatnagar
Julu
J
Sumner
John
J
Liu
Lindy
L
Patel
Mitesh
M
Batten
Brigid
B
Greer
Patricia
P
Jones
Tara
T
Smith
Chalanda
C
Bartlett
Jeanine
J
Montague
Jeltley
J
White
Elizabeth
E
Rollin
Dominique
D
Gao
Rongbao
R
Seales
Cynthia
C
Jost
Heather
H
Metcalfe
Maureen
M
Goldsmith
Cynthia S
CS
Humphrey
Charles
C
Schmitz
Ann
A
Drew
Clifton
C
Paddock
Christopher
C
Uyeki
Timothy M
TM
Zaki
Sherif R
SR
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