H1N1 2009 influenza virus infection during pregnancy in the USA.
BACKGROUND
Pandemic H1N1 2009 influenza virus has been identified as the cause of a widespread outbreak of febrile respiratory infection in the USA and worldwide. We summarised cases of infection with pandemic H1N1 virus in pregnant women identified in the USA during the first month of the present outbreak, and deaths associated with this virus during the first 2 months of the outbreak.


METHODS
After initial reports of infection in pregnant women, the US Centers for Disease Control and Prevention (CDC) began systematically collecting additional information about cases and deaths in pregnant women in the USA with pandemic H1N1 virus infection as part of enhanced surveillance. A confirmed case was defined as an acute respiratory illness with laboratory-confirmed pandemic H1N1 virus infection by real-time reverse-transcriptase PCR or viral culture; a probable case was defined as a person with an acute febrile respiratory illness who was positive for influenza A, but negative for H1 and H3. We used population estimates derived from the 2007 census data to calculate rates of admission to hospital and illness.


RESULTS
From April 15 to May 18, 2009, 34 confirmed or probable cases of pandemic H1N1 in pregnant women were reported to CDC from 13 states. 11 (32%) women were admitted to hospital. The estimated rate of admission for pandemic H1N1 influenza virus infection in pregnant women during the first month of the outbreak was higher than it was in the general population (0.32 per 100 000 pregnant women, 95% CI 0.13-0.52 vs 0.076 per 100 000 population at risk, 95% CI 0.07-0.09). Between April 15 and June 16, 2009, six deaths in pregnant women were reported to the CDC; all were in women who had developed pneumonia and subsequent acute respiratory distress syndrome requiring mechanical ventilation.


CONCLUSIONS
Pregnant women might be at increased risk for complications from pandemic H1N1 virus infection. These data lend support to the present recommendation to promptly treat pregnant women with H1N1 influenza virus infection with anti-influenza drugs.


BACKGROUND
US CDC.
Jamieson
Denise J
DJ
National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, GA 30341-3717, USA. DJamieson@cdc.gov
Honein
Margaret A
MA
Rasmussen
Sonja A
SA
Williams
Jennifer L
JL
Swerdlow
David L
DL
Biggerstaff
Matthew S
MS
Lindstrom
Stephen
S
Louie
Janice K
JK
Christ
Cara M
CM
Bohm
Susan R
SR
Fonseca
Vincent P
VP
Ritger
Kathleen A
KA
Kuhles
Daniel J
DJ
Eggers
Paula
P
Bruce
Hollianne
H
Davidson
Heidi A
HA
Lutterloh
Emily
E
Harris
Meghan L
ML
Burke
Colleen
C
Cocoros
Noelle
N
Finelli
Lyn
L
MacFarlane
Kitty F
KF
Shu
Bo
B
Olsen
Sonja J
SJ
D000293:Adolescent; D000328:Adult; D004196:Disease Outbreaks / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype; D007251:Influenza, Human / Q000453:epidemiology* / Q000401:mortality; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000453:epidemiology* / Q000401:mortality; D014481:United States / Q000453:epidemiology; D055815:Young Adult