Photo: Happy faet on Wikimedia Commons
Photo: Happy faet on Wikimedia Commons

How long after COVID symptoms do you actually shed live virus?

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Peer-reviewed: This work was reviewed and scrutinised by relevant independent experts.

Observational study: A study in which the subject is observed to see if there is a relationship between two or more things (eg: the consumption of diet drinks and obesity). Observational studies cannot prove that one thing causes another, only that they are linked.

People: This is a study based on research using people.

Once COVID-19 symptoms begin, the virus is live and can be grown for around seven days, according to US research, while people can still test positive for up to 34 days. Our current COVID-19 tests look for viral genetic material rather than live virus, so researchers from Korea were keen to see how long people actually shed live viruses that they could grow in culture. The small study of 21 patients found that the longest gap between symptom onset and being able to grow the virus was 12 days. The authors say their findings may be useful in guiding isolation periods for patients with COVID-19 and in estimating the risk of secondary transmission among close contacts in contract tracing.

Journal/conference: New England Journal of Medicine

Link to research (DOI): 10.1056/NEJMc2027040

Organisation/s: Chung-Ang University Hospital, South Korea

Funder: Supported by Chung-Ang University Research Grants in 2020 (to Dr. Kim) and by a grant (NRF-2018M3A9H4056537, to Dr. Park) from the National Research Foundation of Korea, funded by the Ministry of Science and Information and Communication Technology.

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