WASHINGTON -- A new study published on March 31 by Science magazine suggests that the lockdown of Wuhan, capital of central China's Hubei Province, combined with the Level 1 national emergency response, averted hundreds of thousands of COVID-19 cases in China by Feb 19.

The study, led by Tian Huaiyu of Beijing Normal University, focused on the development of the epidemic in the first 50 days in China, which ended on Feb 19.

To more quantitively investigate the impact of travel restrictions and social distancing measures on infection spread, the researchers used a unique geocoded repository of data on COVID-19 epidemiology, human movement, and public health intervention in China in an analysis that spanned from Dec. 31, 2019 to Feb 19, 2020.

During this period, China imposed a travel ban on Wuhan, where the outbreak first started, on Jan. 23 and raised its national public health response to the highest state: Level 1, including suspended public transport, closed entertainment venues, and bans on large public gatherings.

On average, the travel ban delayed the arrival time of COVID-19 in cities by an estimated 2.91 days, according to the study.

Cities that implemented a Level 1 response before cases were reported had 33.3 percent fewer laboratory-confirmed cases during the first week of their outbreaks, the data show.

Without the travel ban on Wuhan or the national emergency response, there would have been approximately 744,000 confirmed COVID-19 cases outside Wuhan by Feb 19, the model suggests.

With the ban alone, there would have been approximately 202,000 cases; and while with the national emergency response alone, the figure would have decreased to roughly 199,000, according to the study.

Neither intervention alone would have reversed the rise in incidence by Feb 19. But together, they offer an explanation for limiting the number of confirmed cases to 29,839, 96 percent fewer than expected in the absence of interventions by day 50, according to the study.