Objective From November 24 to December 9, 2013, an outbreak of the influenza (flu) A (H3) virus occurred in a tertiary-care university hospital (1,014 beds). We herein report the prophylactic effect of anti-flu agents for controlling the flu outbreak. Methods We administered pre- or post-exposure prophylaxis with anti-flu agents in flu outbreak. To test the effectiveness of prophylaxis in a flu outbreak, we used the posterior mean of the reproductive value during the pre- and post-intervention period. We also simulated the probability distribution of new flu cases. We performed an analysis to quantify the strength of the intervention effect. Results A total of 97 people were diagnosed with flu before the intervention, and 7 were diagnosed after the intervention. A molecular analysis of the flu virus revealed that this outbreak was due to the flu A (H3) virus. A total of 3,702 people received prophylaxis. There was a significant reduction in the reproductive value from 1.89 [95% confidence interval (CI), 1.59 to 2.24] to 0.65 (95% CI, 0.02 to 1.00) after the intervention (p<0.001). Conclusion Prophylaxis with anti-flu agents, along with prompt identification and isolation of infected individuals, was effective in reducing the impact of a flu outbreak in a hospital.
Keywords: influenza (flu); oseltamivir; outbreak; prophylaxis; zanamivir.