A new study from an international team of experts – including a University of Washington School of Public Health biostatistician – examines the effect of travel restrictions on the spread of the novel coronavirus that causes the respiratory disease now known as the coronavirus disease 2019 (COVID-19).

The study found that while travel bans did not prevent the spread of the virus, they did slow its progression for a short period, which could be instrumental for public health response planning. It also determined that reducing transmissibility had a bigger impact on controlling the epidemic than travel restrictions alone.

The paper was published March 6 in Science.

The study’s modeling found that the travel ban in Wuhan, China, where the virus first emerged, only delayed the spread of COVID-19 to other areas of mainland China by three to five days. However, according to the study, it also reduced the number of infections that spread to other countries by nearly 80% for two to three weeks, after which the number of cases resumed its growth. The study concluded that while travel restrictions have modest effects on the spread of the virus, transmission-reduction interventions will provide the greatest impact on mitigating the epidemic.

”Travel restrictions alone do not really do much but delay the spread of the disease, and delaying is good because it slows things down. But this idea of reducing the transmissibility is really key,” says study co-author Elizabeth Halloran, a professor of biostatistics at the UW School of Public Health and director of the UW Summer Institutes in Statistics and Modeling in Infectious Diseases (SISMID). Halloran is also director of the Center for Inference and Dynamics of Infectious Diseases based at Fred Hutch.

Halloran explains that reducing transmissibility refers to measures such as early detection and isolation of cases, social distancing such as school closures, behavioral changes such has frequent hand washing, and public health awareness efforts.

 “Closing travel might delay the progression of the epidemic in some places and provide some time for preparation,” says corresponding author Alessandro Vespignani, director and Sternberg Family Distinguished Professor of Health Sciences and Computer Sciences at Northeastern University. Vespignani is also an instructor with UW’s Summer Institute program.

“At this point, every day that goes by is more knowledge about the disease. And so, we can act and fight it better.”

Deb Nelson, Biostatistics communications and event manager