Travel restrictions work in limiting spread of coronavirus, study finds

16 Mar 2020

Image: © william87/

A study tracking the spread of coronavirus has found that travel restrictions have worked, at least in China, but a global spread was inevitable.

As countries across the world impose travel restrictions as a result of the coronavirus pandemic, a team of researchers led by Chad Wells of the Center for Infectious Disease Modeling and Analysis at the Yale School of Public Health has looked in detail at how effective this containment measure has been.

The study, published to the Proceedings of the National Academy of Sciences, focused on China’s restrictions as the first country to report the virus. It has found that while travel restrictions have helped lower the speed of the infection rate, they are not effective enough to stop its spread globally, since many who have the virus may show no symptoms.

By the team’s estimates, the daily risk of even a single case of the coronavirus leaving China via international travel exceeded 95pc by 13 January.

However, by 2 January the virus had already reached a point of the greatest likelihood of it having left China, 21 days before the lockdown was initiated in the city of Wuhan.

‘[Measures] are insufficient to contain the global spread of Covid-19’

The team estimated that the number of exported cases would have exceeded 50 by 25 January without border restrictions. This figure was actually reached by 28 January under the enforced lockdown.

During the lockdown, an average of five cases a day were exported from China, marking a 81.3pc average reduction in the exportation rate that may have happened without travel restrictions. Estimates showed that the number of cases of Covid-19 importations was reduced from 779 to 230 as a result of the lockdown.

Effective, but not totally

“We estimated that 64.3pc of exported cases were pre-symptomatic upon arrival at their destination airport,” the authors wrote.

“Assuming that only symptomatic cases were detected by airport screening upon arrival, we estimate that screening contained 82 cases imported from mainland China, while the two travel lockdowns averted 549 cases being exported up to 15 February.”

Examining the effectiveness of self-reporting symptoms prior to arrival at airport, the team found that health questionnaires would catch 95pc of cases during the virus’s incubation period.

Despite these findings showing the potential effectiveness of travel restrictions and limiting the amount of movement within a country, the team does not believe the virus can be contained.

“Our results show that these measures likely slowed the rate of exportation from mainland China to other countries, but are insufficient to contain the global spread of Covid-19,” the report said.

“With most cases arriving during the asymptomatic incubation period, our results suggest that rapid contact tracing is essential both within the epicentre and at importation sites to limit human-to-human transmission outside of mainland China.”

Colm Gorey was a senior journalist with Silicon Republic