International Travel Controls Slowed, But Failed to Stop, Coronavirus

Travel bans, screenings and lockdown procedures were effective in slowing early global spread of the novel coronavirus (COVID-19), but these measures alone were inadequate to contain the epidemic, a new study led by the Yale School of Public Health finds.

The research, published in the journal Proceedings of the National Academy of Sciences, sheds light on how public health should respond to future pandemics and what the best course of action could be to limit exportation of a disease from its epicenter. The study is the first on COVID published by the Yale School of Public Health.

“Although the enhanced disease control in Wuhan, China, slowed the exportation of infected individuals, we estimated that the first importation event occurred roughly three weeks before the government enforced travel restrictions,” said Chad R. Wells, a postdoctoral research associate at the Yale School of Public Health’s Center for Infectious Disease Modeling and Analysis (CIDMA).

The first cases of COVID-19 were recorded in Wuhan last December and within a few weeks the disease had spread to 24 countries in different regions of the world. By February 21, just three months later, more than 76,000 cases were recorded globally. That number does not account for silent carriers, people who did not present for testing, or those who tried to test but were refused.

The study also highlights that airport screenings implemented in many countries were not fully effective. The researchers estimate that the majority of travelers with the disease were in the pre-symptomatic phase when they deplaned, so it would have been difficult or impossible to prevent disease importation through screening alone. Screenings, coupled with travel restrictions, slowed the rate of exportation of COVID-19-positive travelers, but were insufficient to stop it altogether.

In addition, the researchers examined the effectiveness of lockdown enforcement in Wuhan and 15 other cities in Hubei Province in China on January 24, 2020. They estimate that 779 cases would have been exported by February 15, 2020, if this measure wasn’t taken. The Chinese government’s actions averted 71% of these cases from traveling.

The study used daily incidence data of the COVID-19 outbreak within mainland China from December 8, 2019, to February 15, 2020 and airline network data to model the number of exported cases with and without travel restrictions and screenings.

“Unfortunately, the United States squandered the time that the travel restrictions gave us. We should have been preparing for this outbreak,” said Alison P. Galvani, director of CIDMA and the Burnett and Stender Families Professor of Epidemiology. “Instead, our hospitals are ill-equipped to treat patients or to even protect courageous frontline workers from themselves becoming infected.”

Other Yale authors included Pratha Sah and Affan Shoukat, postdoctoral associates at CIDMA, as well as research faculty members Abhishek Pandey and Zheng Wang. They collaborated with the Agent-Based Modelling Laboratory of York University, the Department of Integrative Biology of the University of Texas, the Santa Fe Institute and the Emerging Pathogens Institute of the University of Florida.

Find full study here.