Effects of Face Mask Use, Disinfection, and Social Distancing on Household SARS-CoV-2 Transmission

In an era of rapid international spread of COVID-19, with no vaccine or very effective treatments available, containment of the pandemic mainly relies on minimizing social contacts, use of face masks, and disinfection. However, how effective these measures are remains unclear. Researchers in China, where more than 70% of SARS-CoV-2 transmission occurred in families, now confirm the effectiveness of these measures in a retrospective cohort study on secondary transmission in 124 families of laboratory confirmed COVID-19 cases. Participants completed detailed questionnaires on their living arrangements, social activities, and hygiene practices from 4 days before illness onset to the day the index case was identified.

During a 2-week period after symptom onset of the index case in a family, 77 secondary cases occurred in 41 families (median of 2 secondary cases per index case), whereas no secondary transmission was noted in 83 families. Secondary transmission was significantly lower to children ≤18 years old than to adults (36% vs. 70%, respectively). In a multivariable regression model, the risk for COVID-19 transmission in a household was significantly increased with frequent daily close contact with the index case (odds ratio with ≥4 contact times, 18.3), and if the index case had diarrhea (OR, 4.1) and significantly decreased with face-mask wearing by the index case, family members, or both before the index case developed symptoms (OR, 0.2) and with regular daily use of disinfectant in the household (OR, 0.2).