Presumptive summer influenza A: an outbreak on a trans-Tasman cruise.

A number of recent reports from the Northern Hemisphere have drawn attention to the occurrence of summer outbreaks (May to August) of influenza A among cruise ship passengers and their contacts. In cases amongst passengers returning to Canada from Alaska, exposure appears to have occurred during the land-based Alaskan tour with illness developing during the subsequent cruise. A late summer outbreak of influenza A among passengers and crew on the return leg of a 14-day Sydney-New Zealand-Sydney cruise is reported in this article.