Responding to an outbreak of SARS-CoV-2, a novel coronavirus that causes the COVID-19 disease, in December 2019, China banned travel to and from Wuhan city on January 23, 2020, and implemented a national emergency response. According to a new study, these control measures during the first 50 days of the epidemic delayed the spread of the virus to cities outside of Wuhan by 2.91 days and prevented 744,000 infections across the country.
Tian et al investigated the spread and control of COVID-19 in China using a unique data set including case reports, human movement and public health interventions. Image credit: Gerd Altmann.
“The number of confirmed cases in China by day 50 (February 19, 2020) of the epidemic, was around 30,000,” said University of Oxford’s Professor Christopher Dye.
“Our analysis suggests that without the Wuhan travel ban and the national emergency response there would have been more than 700,000 confirmed COVID-19 cases outside of Wuhan by that date.”
“China’s control measures appear to have worked by successfully breaking the chain of transmission — preventing contact between infectious and susceptible people.”
Professor Dye and colleagues used a unique combination of case reports, human movement data and public health intervention information to investigate the spread and control of COVID-19.
The reserchers examined the movements of 4.3 million people out of Wuhan before the travel ban, the types and timing of control measures implemented across the cities of China and the numbers of COVID-19 cases reported each day in every city.
“One fascinating aspect of our work is that it shows the power of novel data streams such as cell phone mobility data,” said Penn State Professor Ottar Bjornstad.
“Since the time period we studied included the Spring Festival holiday and Chinese Lunar New Year, we were able to compare patterns of travel into and out of Wuhan during the outbreak with cell phone data from two previous spring festivals.”
“The analysis revealed an extraordinary reduction in movement following the travel ban of January 23, 2020.”
“Based on these data, we could also calculate the likely reduction in Wuhan-associated cases in other cities across China.”
The team’s model also analyzed the specific effects of the Wuhan shutdown and found that it delayed the arrival of COVID-19 in other cities by several days.
“This delay provided extra time to prepare for the arrival of COVID-19 in more than 130 cities,” Dr. Huaiyu Tian of Beijing Normal University.
“These cities banned public gatherings, closed entertainment venues and suspended public transport, among other actions. As a result, they reported 33% fewer confirmed cases during the first week of their outbreaks than cities that did not implement a Level 1 Response.”
While the control measures taken thus far have reduced the number of COVID-19 infections to very low levels, China, is by no means out of the woods.
“Given the small fraction of the Chinese population that has been infected, a much larger number of people remains at risk of COVID-19,” Dr. Tian said.
“We are acutely aware that resident or imported infections could lead to a resurgence of transmission.”
“SARS-CoV-2 may establish as a human endemic globally in the years to come,” Professor Bjornstad said.
“It is critical to keep in mind that this virgin epidemic likely will affect people of different ages and susceptibilities, and therefore have different fatality levels, than possible subsequent seasonal epidemics.”
The study appears in the journal Science.
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Huaiyu Tian et al. An investigation of transmission control measures during the first 50 days of the COVID-19 epidemic in China. Science, published online March 31, 2020; doi: 10.1126/science.abb6105
