Patients hospitalized with 2009 pandemic influenza A (H1N1) - New York City, May 2009.

The first cases of 2009 pandemic influenza A (H1N1) in New York City occurred in April 2009, raising many questions about how best to contain the epidemic. To rapidly assess the severity of influenza illness and identify persons at highest risk for severe infection, the New York City (NYC) Department of Health and Mental Hygiene (DOHMH) reviewed the medical charts of the first 99 patients with laboratory confirmed H1N1 admitted to any NYC hospital. The purpose of the review was to characterize the demographics of the first hospitalized patients, identify associated underlying medical conditions, describe the course and severity of disease, and examine the use of antiviral medications. This report summarizes the findings of this analysis. Approximately 60% of admitted patients were aged <;18 years. The most commonly documented underlying condition was asthma, observed among 50% of patients aged <18 years and 46% of adult patients. Multiple underlying conditions were observed in 17% of patients (12% of children, 24% of adults). Patients treated with oseltamivir within 2 days of symptom onset had shorter median hospitalizations than those who did not (2 days versus 3 days [p = 0.03]). The findings of this assessment were used to inform immediate outbreak response measures in New York City. During such outbreaks, public education campaigns should encourage patients at high risk of severe illness to seek treatment promptly after symptom onset and should emphasize the importance of early antiviral therapy for patients with underlying risk conditions.