Hospitalized patients with 2009 H1N1 influenza in the United States, April-June 2009.
BACKGROUND
During the spring of 2009, a pandemic influenza A (H1N1) virus emerged and spread globally. We describe the clinical characteristics of patients who were hospitalized with 2009 H1N1 influenza in the United States from April 2009 to mid-June 2009.


METHODS
Using medical charts, we collected data on 272 patients who were hospitalized for at least 24 hours for influenza-like illness and who tested positive for the 2009 H1N1 virus with the use of a real-time reverse-transcriptase-polymerase-chain-reaction assay.


RESULTS
Of the 272 patients we studied, 25% were admitted to an intensive care unit and 7% died. Forty-five percent of the patients were children under the age of 18 years, and 5% were 65 years of age or older. Seventy-three percent of the patients had at least one underlying medical condition; these conditions included asthma; diabetes; heart, lung, and neurologic diseases; and pregnancy. Of the 249 patients who underwent chest radiography on admission, 100 (40%) had findings consistent with pneumonia. Of the 268 patients for whom data were available regarding the use of antiviral drugs, such therapy was initiated in 200 patients (75%) at a median of 3 days after the onset of illness. Data suggest that the use of antiviral drugs was beneficial in hospitalized patients, especially when such therapy was initiated early.


CONCLUSIONS
During the evaluation period, 2009 H1N1 influenza caused severe illness requiring hospitalization, including pneumonia and death. Nearly three quarters of the patients had one or more underlying medical conditions. Few severe illnesses were reported among persons 65 years of age or older. Patients seemed to benefit from antiviral therapy.
Jain
Seema
S
Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA. bwc8@cdc.gov
Kamimoto
Laurie
L
Bramley
Anna M
AM
Schmitz
Ann M
AM
Benoit
Stephen R
SR
Louie
Janice
J
Sugerman
David E
DE
Druckenmiller
Jean K
JK
Ritger
Kathleen A
KA
Chugh
Rashmi
R
Jasuja
Supriya
S
Deutscher
Meredith
M
Chen
Sanny
S
Walker
John D
JD
Duchin
Jeffrey S
JS
Lett
Susan
S
Soliva
Susan
S
Wells
Eden V
EV
Swerdlow
David
D
Uyeki
Timothy M
TM
Fiore
Anthony E
AE
Olsen
Sonja J
SJ
Fry
Alicia M
AM
Bridges
Carolyn B
CB
Finelli
Lyn
L
D000293:Adolescent; D000328:Adult; D000368:Aged; D000998:Antiviral Agents / Q000627:therapeutic use; D001249:Asthma / Q000453:epidemiology; D015992:Body Mass Index; D002318:Cardiovascular Diseases / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D015897:Comorbidity; D005260:Female; D017052:Hospital Mortality; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics / Q000302:isolation & purification; D007251:Influenza, Human / Q000453:epidemiology* / Q000401:mortality / Q000628:therapy; D007362:Intensive Care Units / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D011247:Pregnancy; D011248:Pregnancy Complications / Q000453:epidemiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012307:Risk Factors; D016896:Treatment Outcome; D014481:United States / Q000453:epidemiology; D055815:Young Adult
D000998:Antiviral Agents