The lockdown of the first Covid-19 pandemic epicentre Wuhan city and the highest emergency response put in place in the rest of China delayed the spread of the outbreak and reduced case numbers by hundreds of thousands by February 19, a new study published this week said.
Drawing inferences from statistical and mathematical analyses of human mobility and transmission control measures, the study said “…control measures were strongly associated with the containment of Covid-19, potentially averting hundreds of thousands of cases by February 19, day 50 of the epidemic.”
The study published in the academic journal Science on Tuesday was conducted by 22 scientists from China, the US, and the UK.
To quantitatively investigate the impact of travel restrictions and social distancing measures on infection spread, according to Chinese state media, 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 December 31, 2019, to February 19, 2020.
The epicentre Wuhan was put under a lockdown within that period, on January 23, as China was shutting down for the Chinese New Year (CNY) holidays.
“In summary, this analysis shows that transmission control (non-pharmaceutical) measures initiated during CNY holidays, including the unprecedented Wuhan city travel ban and the Level 1 national emergency response, were strongly associated with, though not necessarily the cause of, a delay in epidemic growth and a reduction in case numbers during the first 50 days of the Covid-19 epidemic in China,” the researchers said.
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 February 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 199000,” according to the study.
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% fewer laboratory-confirmed cases during the first week of their outbreaks, the data show.
The analysis showed that “…suspending intra-city public transport, closing entertainment venues and banning public gatherings, which were introduced at different times in different places, were associated with the overall containment of the epidemic.”
The authors noted the limitations of the study including that the “…number of people who have developed Covid-19 during this epidemic, and therefore the number of people who were protected by control measures, is not known precisely, given that cases were almost certainly under-reported”.
“However, in view of the small fraction of people known to have been infected by February 19 (75,532 cases, 5.41 per 100,000 population), it is unlikely that the spread of infection was halted and epidemic growth reversed because the supply of susceptible people had been exhausted,” the researchers inferred.
The study adds a note of caution because the number of “susceptibles” in China is far from over.
“This implies that a large fraction of the Chinese population remains at risk of Covid-19; control measures may need to be reinstated, in some form, if there is a resurgence of transmission.”
The study also puts a question mark on whether the same model can be replicated elsewhere.
“Whether the means and the outcomes of control can be replicated outside China, and which of the interventions are most effective, are now under intense investigation as the virus continues to spread worldwide”.