COVID-19 patients may be most infectious between 2 days before and 3 days after symptoms start

Embargoed until: Publicly released: 2021-08-24 01:00

International

Close contacts may be at more risk of catching COVID-19 if they had contact with an infected person in the period between two days before and three days after when that person first showed symptoms, according to a US and Chinese study. The study involved 8,852 contacts of 730 index cases, and was carried out from Jan to Aug 2020. The greatest risk was on the day that symptoms first showed up in the index case. Also, when the case didn’t have any symptoms, infected close contacts were less likely to catch COVID-19 - and if they did, they were less likely to have symptoms themselves. The authors say this suggests the severity of the index case may be linked with the likelihood and severity of illness for close contacts.

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conference: JAMA Internal Medicine

Research:Paper

Organisation/s: University of Georgia, Boston University (US), Zhejiang Provincial Center for Disease Control and Prevention (China), University of Texas, etc.

Funder: Funding/Support: This study was supported by the Zhejiang Basic Public Welfare Research Project (grant LGF21H260003; Dr Ling). Role of the Funder/Sponsor: The funding source had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication. Additional Contributions: We thank the staff members of all district-level Zhejiang Provincial Centers for Disease Control and Prevention and community health service centers in Zhejiang for their assistance in field investigation and data collection. These individuals were not compensated for their contributions beyond their normal salaries.

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