Open Access Highly Accessed Research article

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

Benjamin J Cowling1*, Lincoln LH Lau1, Peng Wu1, Helen WC Wong2, Vicky J Fang1, Steven Riley1 and Hiroshi Nishiura34

Author Affiliations

1 School of Public Health, The University of Hong Kong, Hong Kong Special Administrative Region, People's Republic of China

2 Imperial College London, London, UK

3 Theoretical Epidemiology, University of Utrecht, Utrecht, The Netherlands

4 PRESTO, Japan Science and Technology Agency, Saitama, Japan

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BMC Infectious Diseases 2010, 10:82  doi:10.1186/1471-2334-10-82

Published: 30 March 2010



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.


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.


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.


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.