Update: outbreak of influenza A infection--Alaska and the Yukon Territory, July-August 1998.

On July 26, 1998, CDC and Health Canada, in cooperation with local public health authorities, began investigating reports of febrile respiratory illnesses and associated pneumonia among summer land and sea travelers to Alaska and the Yukon Territory (1). Epidemiologic and laboratory evidence has implicated influenza A virus as the etiologic agent of the outbreak. From June 11 through August 22, completed viral cultures of 101 (48%) of 209 nasopharyngeal specimens have yielded 26 influenza A isolates, four other respiratory viruses, and 71 negative results; results are pending for 108 additional specimens. Of the 26 influenza A isolates, five have been characterized at CDC; all have been identified as influenza A/Sydney/5/97 (H3N2)-like viruses, a strain included in the 1998-99 influenza vaccine. This report presents updated information about the outbreak and includes recommendations for influenza A prevention and control in this setting.