Open Access Open Badges Research article

Asthma in patients hospitalized with pandemic influenza A(H1N1)pdm09 virus infection–United States, 2009

John J McKenna123*, Anna M Bramley1, Jacek Skarbinski1, Alicia M Fry1, Lyn Finelli1, Seema Jain1 and for the 2009 Pandemic Influenza A (H1N1) Virus Hospitalizations Investigation Team; 1600 Clifton Road, MS-A32, Atlanta, GA 30333

Author affiliations

1 Influenza Division, Centers for Disease Control and Prevention Atlanta, Atlanta, GA, USA

2 The CDC Experience Applied Epidemiology Fellow, Atlanta, GA, USA

3 Present address: 1929 Huxley St., Madison, WI, 53704, USA

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Citation and License

BMC Infectious Diseases 2013, 13:57  doi:10.1186/1471-2334-13-57

Published: 31 January 2013



Asthma was the most common co-morbidity among patients hospitalized with pandemic influenza A(H1N1)pdm09 [pH1N1] infection. The objective was to compare characteristics of hospitalized pH1N1 patients with and without asthma and assess factors associated with severity among asthma patients.


Patient data were derived from two 2009 pandemic case-series of U.S. pH1N1 hospitalizations. A case was defined as a person ≥ 2 years old hospitalized with laboratory-confirmed pH1N1. Asthma status was determined through chart review.


Among 473 cases, 29% had asthma. Persons with asthma were more likely to be 2–17 years old (39% vs. 30%, p = 0.04) and black (29% vs. 18%, p < 0.01), and have chronic obstructive pulmonary disease (13% vs. 9%, p = 0.04) but less likely to have pneumonia (37% vs. 47%, p = 0.05), need mechanical ventilation (13% vs. 23%, p = 0.02), and die (4% vs. 10%, p = 0.04) than those without asthma. Among patients with asthma, those admitted to an intensive care unit (ICU) or who died (n = 38) compared with survivors not admitted to an ICU (n = 99) were more likely to have pneumonia on admission (60% vs. 27%, p < 0.01) or acute respiratory distress syndrome (24% vs. 0%, p < 0.01) and less likely to receive influenza antiviral agents ≤ 2 days of admission (73% vs. 92%, p = 0.02).


The majority of persons with asthma had an uncomplicated course; however, severe disease, including ICU admission and death, occurred in asthma patients who presented with pneumonia. Influenza antiviral agents should be started early in hospitalized patients with suspected influenza, including those with asthma.

Asthma; Influenza A virus; Hospitalization; ICU; H1N1pdm09