Entry screening to delay local transmission of 2009 pandemic influenza A (H1N1)

Cowling, Benjamin J; Lau, Lincoln LH; Wu, Peng; Wong, Helen WC; Fang, Vicky J; Riley, Steven; Nishiura, Hiroshi

BACKGROUND: After the WHO issued the global alert for 2009 pandemic influenza A (H1N1), many national health agencies began to screen travelers on entry in airports, ports and border crossings to try to delay local transmission. METHODS: We reviewed entry screening policies adopted by different nations and ascertained dates of official report of the first laboratory-confirmed imported H1N1 case and the first laboratory-confirmed untraceable or 'local' H1N1 case. RESULTS: Implementation of entry screening policies was associated with on average additional 7-12 day delays in local transmission compared to nations that did not implement entry screening, with lower bounds of 95% confidence intervals consistent with no additional delays and upper bounds extending to 20-30 day additional delays. CONCLUSIONS: Entry screening may lead to short-term delays in local transmission of a novel strain of influenza virus. The resources required for implementation should be balanced against the expected benefits of entry screening.