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Reduction of secondary transmission of SARS-CoV-2 in households by face mask use, disinfection and social distancing: a cohort study in Beijing, China
  1. Yu Wang1,
  2. Huaiyu Tian2,
  3. Li Zhang1,
  4. Man Zhang3,
  5. Dandan Guo4,
  6. Wenting Wu1,
  7. Xingxing Zhang3,
  8. Ge Lin Kan5,
  9. Lei Jia1,
  10. Da Huo1,
  11. Baiwei Liu1,
  12. Xiaoli Wang1,
  13. Ying Sun1,
  14. Quanyi Wang1,
  15. Peng Yang3,
  16. C. Raina MacIntyre6,7
  1. 1 Institute for Infectious Disease and Endemic Disease Control, Beijing Center for Disease Prevention and Control, Beijing Research Center for Preventive medicine, Beijing, China
  2. 2 State Key Laboratory of Remote Sensing Science, College of Global Change and Earth System Science, Beijing Normal University, Beijing, China
  3. 3 Office of Beijing Center for Global Health, Beijing Center for Disease Prevention and Control, Beijing Research Center for Preventive medicine, Beijing, China
  4. 4 Institute for nutrition and food hygiene, Beijing Center for Disease Prevention and Control, Beijing Research Center for Preventive medicine, Beijing, China
  5. 5 Department of Environmental and Occupational Health, School of Public Health, University of Nevada, Las Vegas, Nevada, USA
  6. 6 Arizona State University College of Health Solutions, Phoenix, Arizona, USA
  7. 7 Kirby institute, Faculty of Medicine, the University of New South Wales, Sydney, New South Wales, Australia
  1. Correspondence to Dr Quanyi Wang; wangquanyi{at}; Dr Peng Yang; yangpengcdc{at}


Introduction Transmission of COVID-19 within families and close contacts accounts for the majority of epidemic growth. Community mask wearing, hand washing and social distancing are thought to be effective but there is little evidence to inform or support community members on COVID-19 risk reduction within families.

Methods 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 outcome of interest was secondary transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) within the family. Characteristics and practices of primary cases, of well family contacts and household hygiene practices were analysed as predictors of secondary transmission.

Results 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 (OR=0.21, 95% CI 0.06 to 0.79). Daily use of chlorine or ethanol based disinfectant in households was 77% effective (OR=0.23, 95% CI 0.07 to 0.84). Wearing a mask after illness onset of the primary case was not significantly protective. The risk of household transmission was 18 times higher with frequent daily close contact with the primary case (OR=18.26, 95% CI 3.93 to 84.79), and four times higher if the primary case had diarrhoea (OR=4.10, 95% CI 1.08 to 15.60). Household crowding was not significant.

Conclusion The study confirms the highest risk of transmission prior to symptom onset, and provides the first evidence of the effectiveness of mask use, disinfection and social distancing in preventing COVID-19. We also found evidence of faecal transmission. This can inform guidelines for community prevention in settings of intense COVID-19 epidemics.

  • public health
  • infections, diseases, disorders, injuries
  • cohort study

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  • Handling editor Seye Abimbola

  • Contributors All authors approved the final draft of the manuscript. The corresponding authors attests that all listed authors meet authorship criteria and that no others meeting the criteria have been omitted.

  • Funding This work was supported by Beijing Science and Technology Planning Project (Z201100005420010).

  • Competing interests None declared.

  • Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

  • Patient consent for publication Not required.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement No additional data available.