COVID Survivors May Need Test a Month Later
By Steven Reinberg
THURSDAY September 3, 2020 (HealthDay News) – You tested positive for COVID-19 and dutifully quarantined yourself for two weeks to avoid infecting others. Now you feel better and you think you are safe for your friends or family, right?
Not necessarily, says a new study that shows it takes about a month to completely clear the coronavirus from your body. To be sure, patients with COVID-19 must be retested after four weeks or more to be sure the virus is not always active, according to Italian researchers.
Whether you are still infectious within a month of your diagnosis is a roll of the dice: the test used in the study, an RT-PCR nasal swab, had a false negative rate of 20%. This means that one in five results that are negative for COVID-19 are false, and patients can still make others sick.
“The timing of re-testing people with COVID-19 in isolation is relevant for identifying the best follow-up protocol,” said lead researcher Dr Francesco Venturelli, from the epidemiology unit at Azienda Unita Sanitaria Locale – IRCCS in di Reggio Emilia.
“Nevertheless, the results of this study clearly underline the importance of producing evidence on the duration of the infectivity of SARS-CoV-2 to avoid unnecessary isolation without increasing the risk of viral spread in clinically recovered people”, a- he added.
For the study, the researchers followed nearly 4,500 people with COVID-19 between February 26 and April 22, 2020, in the province of Reggio Emilia in Italy.
Of these patients, nearly 1,260 cleared the virus and more than 400 died. It took an average of 31 days for someone to clear the virus after the first positive test.
Each patient was tested on average three times: 15 days after the first positive test; 14 days after the second; and nine days after the third.
Investigators found that about 61% of patients had cleared the virus. But there was a false negative rate of just under a quarter of the tests.
The mean time to elimination was 30 days after the first positive test and 36 days after the onset of symptoms. As the age and severity of the infection increased, it took a little longer to clear the infection, the researchers noted.
“In countries where the screening strategy for tracking people with COVID-19 requires at least one negative test to end isolation, this evidence supports the assessment of the most effective and safest time for them. new tests – ie 30 days after disease onset, ”Venturelli said.
The report was published online on September 3 in the BMJ open.
Dr Marc Siegel, professor of medicine at NYU Langone Medical Center in New York City, agreed that further testing was needed to make sure the virus was no longer present.
“The advice for patients is to get tested again a month after your initial test,” he said. “What is new here is the discovery that the speed of viral clearance does not occur in a day, but in 30 days.”
Siegel said that when a blood test for COVID-19 is perfected, it would be the best option to use to reduce the possibility of false negative results.
The only caveat to take away, he said, is that this shouldn’t take testing away from people who need it to diagnose COVID-19. With testing still scarce, it may be necessary to wait until new antigen tests become widely available, he noted.
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