Social distancing prevented more than 94% of coronavirus infections in China’s Hubei Province, according to a new study awaiting peer review. 

Using a statistical model, investigators tracked virus transmission and disease severity from early in the outbreak through the time when authorities officially locked down most of the province. 

The attack rate rose steadily to a peak and then substantially declined after population-wide government interventions were put in place. At that time, illness dropped across geographic regions, sex and age groups, except in children younger than age 20, whose attack rate increased, reported lead author Professor Tangchun Wu. The highest illness rates were seen among healthcare workers and the elderly. Severity risk increased with age.

The model suggests that people moving freely with undetected disease may have contributed to the virus’s quick spread before the lockdown. At least 59% of infected individuals were in contact with others early on, probably transmitting the infection, Wu and colleagues estimated.

“Considerable countermeasures have effectively controlled the Covid-19 outbreak in Wuhan,” concluded Wu. “In the future, special efforts are needed to protect vulnerable populations, including healthcare workers, elderly and children.”

The study abstract has been released online by preprint server medRxiv.