The COVID-19 pandemic has brought tighter restrictions on the daily lives of millions of people, but we do not yet understand what measures are the most effective. This study modeled virus transmission in Wuhan, China, in February 2020, investigating the effects of interventions ranging from patient management to social isolation.

The authors first estimated age-mixing patterns using contact surveys conducted in Wuhan and Shanghai at the beginning of February 2020. They found that that children 0-14 years are less susceptible to SARS-CoV-2 infection than adults 15-64 years of age (odd ratio 0.34, 95%CI 0.24-0.49), while in contrast, individuals over 65 years are more susceptible to infection (odd ratio 1.47, 95%CI: 1.12-1.92).

Using these data, they built a transmission model to study the impact of social distancing and school closure on transmission. They found that social distancing alone – as implemented in China during the outbreak – was sufficient to control COVID-19. Specifically, once people reduced their average daily contacts from 14 to 20 down to 2, transmission rapidly fell below the epidemic threshold, and limiting human mixing to within households appeared to be the most effective measure. School closures, while insufficient to reduce transmission on their own, reduced peak incidence by 40-60%.