Zanamivir use during transmission of amantadine-resistant influenza A in a nursing home

Background: Nursing home influenza outbreaks are common. Amantadine is effective for prophylaxis, but fails to control all outbreaks. We describe an outbreak of influenza A which continued due to amantadine resistance. Zanamivir use was associated with termination of the outbreak. Outbreak: The outbreak occurred in a 176-bed residential home for the elderly. Cases of respiratory illness started on March 5, and three of four nasopharyngeal swabs tested positive for influenza A. Amantadine was given to residents from 9 to 19 March; however, new cases continued to occur. The number of new cases increased to 11 on March 25, and five of six nasopharyngeal swabs tested were positive for influenza A. Despite re-initiation of amantadine, new cases continued. Nine nasopharyngeal swabs yielded amantadine-resistant influenza A. Intervention: Prophylactic zanamivir inhalations were initiated on April 2. Despite the level of dementia, 95% of residents cooperated, 74% had no difficulty with inhalations. Results: In the 2 weeks after the initiation of zanamivir, two new cases of respiratory illness occurred, neither confirmed as influenza A. No side effects were associated with zanamivir. Conclusion: Zanamivir use was associated with termination of an outbreak which amantandine had failed to control. Zanamivir was well tolerated and effective in the control of influenza A.