Pandemic passenger screening

Four major US national laboratories have worked together to develop a computer model to help airport authorities screen passengers for pandemic influenza. The tool can help estimate false negatives, people with influenza who slip through the screening process, and so assess the risk of infected passengers unknowingly spreading disease across the nation.

Robert Brigantic, and colleagues at the Pacific Northwest National Laboratory, in Richland, Washington, and teams at Oak Ridge National Laboratory, Tennessee, Lawrence Berkeley National Laboratory, California, and Los Alamos National Laboratory, New Mexico, report details of their simulations in the current issue of the International Journal of Risk Assessment and Management.

When there is a confirmed human outbreak of a pandemic influenza virus overseas, the US National Strategy for Pandemic Influenza calls for screening of passengers scheduled to fly into the US at international airports, en route screening and arrival screening at US ports-of-entry. However, the efficacy of screening procedures is not known and so Brigantic and colleagues have built a computer model, a simulation of US airport entry screening that combines epidemiology with knowledge about evolving disease states and conditions of passengers over time.

They have tested their simulation under different pandemic scenarios and carried out an analysis of the impact of alternative mitigative, diagnostic and quarantine measures that can be used. Their results could help decision makers plan for the resources needed at the port-of-entry airports, anticipate possible developments during a pandemic, and devise appropriate courses of action to prevent the spread of disease through the US.

"The simulation work is easily adaptable to model other types of outbreaks, to include non-influenza virus type outbreaks or disease spread," says Brigantic.

The researchers conclude that there are several key factors that could reduce the risk of a pandemic influenza spreading widely in the US. First, if possible passengers should be screened before they board a plane bound for the US. Second, passengers presenting symptoms on arrival should be tested for the pandemic influenza virus and potential quarantine. The authorities should be aware that passengers may infect each other before and during their flight and that any screening program is likely to increase delays and queues.

Finally, the team suggests that advances are now needed in diagnostics for infection to automate and speed up confirmation.

May 19, 2009