Reintroduction of influenza A to a nursing building.

We report an outbreak of influenza A from a four-building veterans' facility in King, Wisconsin. Influenza was isolated in 154 of 721 residents over a 121-day period. Building A had 2 cases, no isolates for 40 days, followed by 27 cases. Building B had 25 cases, no isolates for 75 days, followed by 4 cases. Building C had 23 cases, no isolates for 14 days, followed by 17 cases. Influenza A may be reintroduced to a nursing building. Surveillance with contingency plans for restarting of prophylaxis must continue for the duration of influenza in the community.