London School of Hygiene & Tropical Medicine

A recent paper in the New England Journal of Medicine shows that most people are infected with the new coronavirus for just over five days before showing symptoms. Using this information, combined with data on the sensitivity of thermal scanners, the LSHTM team used a mathematical model to estimate that for every 100 infected travellers planning to take a 12 hour flight, only 9 will be detected at entry screening upon arrival.

The model also estimates that 49 passengers would be detected through exit screening before they board, but 42 infected travellers will pass both exit and entry screening undetected. The precise numbers depend on how good screening is at detecting symptoms as well as the time periods between infection and illness. 

Billy Quilty, Research Assistant and PhD student at LSHTM and a member of the modelling team, said: “Entry screening of flights from affected areas appears to be a rational measure to prevent importation of coronavirus cases. However, screening is only able to detect infected travellers who are currently showing symptoms, such as fever.

“Our work reinforces that thermal scanning cannot detect every traveller infected with this new coronavirus. Other policies that can decrease the risk of transmission from imported infected individuals, such as providing information on rapidly seeking care if symptoms develop, are crucial.”

The team have developed an interactive tool so that public health authorities around the world can judge the effectiveness of installing thermal scanners at airports in their country.

This work has not been peer-reviewed. The team acknowledge limitations of this work, including not knowing how many travellers may be infected with the virus.

• LSHTM Viral is a new daily global health podcast focusing on the science behind outbreaks and how we respond to them. Subscribe to hear the latest on the coronavirus outbreak.