The characteristics of household transmission of COVID-19

The characteristics of household transmission of COVID-19.. Spencer EA, Heneghan C.

Published on July 6, 2020

Reference Li W, Zhang B, Lu J et al The characteristics of household transmission of COVID-19. Clin Infect Dis. 2020. 2020
Study type
Country China
Setting Households
Funding Details This work was supported by the National Natural Science Foundation of China (grant number 81902703; to W. L.).
Transmission mode Person to person, Close contact
Exposures Household contact, Family members

Bottom Line

The secondary attack rate of SARS-CoV-2 within households was 16%. Increased age and being the spouse of the index case increased risk of transmission. Isolation within the home of the index patients, at the onset of symptoms, prevented household transmission.

Evidence Summary

Secondary transmission of SARS-CoV-2 developed in 64/392 household contacts (16%). The secondary attack rate for children was 4% compared with 17% for adults. 

The secondary attack rate for households contacts with index patients quarantined by themselves since the onset of symptoms was 0% compared with 17% for contacts with index patients who did not quarantine. 

The secondary attack rate for contacts who were spouses of index cases was 28% compared with 17% for other adult members in the households.

Gender, symptoms, and the time between the onset of illness of the index patients and hospitalization were not related to the secondary attack rates of SARS-CoV-2 to household contacts.

What did they do?

This was a cohort study of households. A total of 105 index patients and 392 household contacts were enrolled in the study for data collection, symptom monitoring and testing for SARS-CoV-2 using real-time PCR testing. Information on all recruited individuals was extracted from medical records and confirmed or supplemented by telephone interviews. 

The baseline characteristics of index cases and contact patients were described. Secondary attack rates of SARS-CoV-2 to contact members were computed and the risk factors for transmission within the household were estimated.

Self-isolating or quarantining at home entailed wearing a face mask, dining separately, and residing alone.

Study reliability

The whole close-contact population of 390 individuals could not be screened by the laboratory test, which may have led to missing asymptomatic cases.
This was a relatively small study so the power to investigate particular factors affecting subgroups was limited.

Clearly defined setting Demographic characteristics described Follow-up length was sufficient Transmission outcomes assessed Main biases are taken into consideration
Yes Yes Yes Yes No

What else should I consider?

About the authors

Carl Heneghan

Carl is Professor of EBM & Director of CEBM at the University of Oxford. He is also a GP and tweets @carlheneghan. He has an active interest in discovering the truth behind health research findings

Elizabeth Spencer

Dr Elizabeth Spencer; MMedSci, PhD. Epidemiologist, Nuffield Department for Primary Care Health Sciences, University of Oxford.