The Wuhan travel ban and a Level-1 national emergency response implemented by China against the COVID-19 outbreak prevented over 700,000 confirmed cases outside Wuhan by Day 50 (February 19) of the epidemic, an international study has found.
The Wuhan shutdown also delayed the growth of the epidemic elsewhere in China, slowing the dispersal of the infection to other cities by an estimated 2.91 days. “Cities that implemented control measures pre-emptively reported 33.3% fewer cases in the first week of their outbreaks compared with cities that started control later,” the study found.
Titled ‘The impact of transmission control measures during the first 50 days of the COVID-19 epidemic in China’ was posted on March 10 on MedRxiv, a preprint server for health sciences. The collaborative study between researchers from the US, UK and China has not been peer-reviewed.
The authors carried out a quantitative analysis of the impact of travel restrictions and transmission control measures during the first 50 days of the epidemic from December 31, 2019 to February 19,2020. The analysis is based on a “unique geocoded repository of data on COVID-19 epidemiology, human movement, and public health (non-pharmaceutical) interventions.”
Without any interventions, the study noted that there would have been 744,000 (± 156,000) confirmed COVID-19 cases outside Wuhan by 19 February, day 50 of the epidemic. “The Wuhan travel ban alone would have reduced this to 202,000 (± 10,000) cases, by delaying epidemic growth and the national emergency response alone would have cut the number of cases to 199,000 (± 8500),” it stated.
While neither of these interventions would have reversed the rise in incidence by February 19, “together and interactively, these control measures evidently did halt and reverse the rise in incidence, limiting the number of confirmed cases reported to 29,839 (fitted model estimate 28,000 ± 1400 cases), a 96% reduction on the total number of cases expected in the absence of interventions,” the study found.
On January 23, China raised its national public health response to Level 1defined as “extremely serious incident.” This meant suspected and confirmed cases were isolated, public transport by bus and subway rail suspended, schools and entertainment venues were closed, public gatherings banned, health checks carried out on migrants (“floating population”), travel prohibited in and out of cities, and information widely disseminated, the study notes.
The study finds firm evidence from the data that suspending intra-city public transport, closing entertainment venues and banning public gatherings which were introduced in different times in different places across China contributed to the overall containment of the epidemic. “Other factors are likely to have contributed to control, such as the isolation of suspected and confirmed patients, contact tracing and the closure of schools, and it is not yet clear which parts of the national emergency response were most effective,” the study notes.
It also noted that “urbanization and the development of rapid transport systems in China probably accelerated the spread and magnified the challenge of controlling COVID-19, as indicated by the comparatively slow dispersal of pandemic influenza H1N1pdm in 2009.” Interestingly, it points out 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 19 February (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,” it noted. “This implies that a large fraction of the Chinese population remains at risk of COVID-19; relaxing control measures could lead to a resurgence of transmission. Further investigations are needed to verify that proposition, and population surveys of infection are needed to reveal the true number of people who have been exposed to this novel coronavirus,” it added.
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