Transmission of Coronavirus disease 2019 (COVID-19) within families and close contacts accounts for the majority of epidemic growth, Wang et al writes in British Medical Journal Global Health.
A retrospective cohort study of 335 people in 124 families and with at least one laboratory confirmed COVID-19 case was conducted from 28 February to 27 March, 2020 in Beijing, China.
The secondary attack rate in families was 23.0% (77/335). Face mask use by the primary case and family contacts before the primary case developed symptoms was 79% effective in reducing transmission.
Daily use of chlorine or ethanol based disinfectant in households was 77% effective.