Outbreak of 2009 pandemic influenza A (H1N1) at a school - Hawaii, May 2009.

The first cases of 2009 H1N1 pandemic influenza were reported by CDC on April 21, 2009. Twenty-one days later, on May 12, the Hawaii Department of Health (HDOH) confirmed two pandemic H1N1 cases from the same school in Oahu. One case was in an 8th-grade student and the other in a 3rd-grade teacher. HDOH initiated an investigation to determine the extent of transmission at the school and among household contacts, and to help establish appropriate control strategies. This report summarizes the results of the investigation, which detected an outbreak of pandemic H1N1 cases at the school over the ensuing 3 weeks. A total of 16 cases were identified; all patients recovered with no hospitalizations or deaths. HDOH, the school, and the Hawaii Department of Education (HDOE) instituted an education campaign asking students and employees to stay home if ill. After consulting with HDOH, school officials decided not to close the school; the outbreak ended after 19 days. This outbreak represented the first documented community transmission of pandemic H1N1 virus in Hawaii. The investigation contributed to the early understanding of the epidemiology of H1N1 influenza in Hawaii (e.g., that risk factors for infection would not be restricted to mainland or foreign travel) and the likely role that endemic transmission would play. Influenza activity in schools can serve to inform local public health officials of changing disease patterns, especially early in an epidemic.