People who’ve had COVID-19 should be swab tested again 4 or more weeks after symptoms first appear to minimise the risk of onward infection, suggests a large population based study in one of Italy’s former coronavirus hotspots, and published in the online journal BMJ Open.
This is because SARS-CoV-2, the virus responsible for COVID-19 infection, takes an average of 30 days to clear from the body after the first positive test result and an average of 36 days after symptoms first appear, the study findings show. And it’s not yet known how infectious a person may be in the recovery phase, warn the researchers.
What’s more, the findings indicate that the rate of false negative test results — whereby people are falsely reassured they no longer have active (shedding) virus in their bodies — is relatively high (1 in 5) in early convalescence, so putting them at risk of unwittingly passing on the infection.
An accurate assessment of how long it takes the body to clear SARS-CoV-2 is key to curbing the risk of onward infection and minimising the enforced isolation period for patients who no longer have symptoms, say the researchers.
To explore this further they tracked the progress of 4538 residents of the Reggio Emilia province in the Emilia-Romagna region of Italy, all of whom tested positive for the virus between February 26 and April 22 this year.
Italy was the first Western country to be badly affected by COVID-19. By mid-April 2020, it ranked third in the world for the number of cases and related deaths. Emilia-Romagna was one of the country’s three coronavirus regional hotspots.