A new COVID-19 transmission model, based on contact survey data from nearly 1200 people in the cities of Wuhan and Shanghai, China, suggests that strict social distancing measures implemented there were sufficient to curtail the transmission of SARS-CoV-2, the virus responsible for the COVID-19 pandemic. The results show that the average resident's daily interpersonal contacts dropped 7- to 9-fold, from 14 and 20 people per day in Wuhan and Shanghai, respectively, to about two contacts per day in both locations by early February, after social distancing measures were put in place. The survey data further show that between 78% and 94% of these contacts occurred at home, between fellow household members, during the social distancing period. Juanjuan Zhang and colleagues used the contact survey data, along with contact tracing data collected in the nearby province of Hunan, to build a mathematical model of SARS-CoV-2 transmission dynamics. Their model results suggest that social distancing measures - and the resulting decrease in daily interpersonal contacts - led transmission rates to drop below epidemic levels in Wuhan and Shanghai, the researchers say. The model also estimated that, in China, children under the age of 15 are about 40% as susceptible to infection with SARS-CoV-2 as elderly people over the age of 64. The model results further suggest that, while school closures helped to stem the rate of disease transmission in China - reducing the overall number of cases and the burden on the healthcare system there - such closures would not have been enough to quell the outbreak. For that, Zhang et al. conclude, it proved necessary to restrict residents' human contact to others residing within their own household.
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Journal
Science