H1N1 attributed to 9 children deaths in California after 2009 outbreak

Louie JK. Arch Pediatr Adolesc Med. 2010;164:1023-1031.

More than one-quarter of California children who were hospitalized with 2009 novel influenza A required intensive care and/or died, according to a study conducted by the California Pandemic Working Group.

Between April 23 and Aug. 11, 2009, there were 1,090 incidents of hospitalization and death caused by novel influenza A (H1N1) in California, of which 345 were in children aged younger than 18 years. Of the 345 children, 27% required intensive care and 3% died of 2009 novel influenza A (H1N1), according to data reported to the California Department of Public Health.

The median time between symptom onset and hospitalization was 2 days. The most common symptoms were fever, cough, shortness of breath, nausea or vomiting, diarrhea and muscle aches. More than half of the patients had pneumonia. More than two-thirds received antiviral treatment.

Comorbid conditions that were considered Advisory Committee on Immunization Practices risk factors for severe influenza were present in 67% of the children, the most common being chronic pulmonary disease (including asthma), underlying neurological disorders (including cerebral palsy/developmental delay and seizure disorder) and immunosuppression. Non-ACIP risk factors such as gastrointestinal disorders and a history of prematurity were present in 28% of the children.

On multivariate analysis, congenital heart disease and cerebral palsy/development delay were associated with increased likelihood of ICU admission and/or death.