the USA

Background Pandemic H1N1 2009 infl uenza virus has been identifi ed 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 identifi ed in the USA during the fi rst month of the present outbreak, and deaths associated with this virus during the fi rst 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 confi rmed case was defi ned as an acute respiratory illness with laboratory-confi rmed pandemic H1N1 virus infection by real-time reverse-transcriptase PCR or viral culture; a probable case was defi ned as a person with an acute febrile respiratory illness who was positive for infl uenza 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.