Researchers say COVID-19 will be retested more than four weeks after the symptoms initially appear to reduce the risk of infection

Those who experience COVID-19 need to be tested with a swab more than 4 weeks after the symptoms first develop and the risk of infection is minimized, one of Italy’s previous coronavirus hotspots. A large population-based study was suggested at and published in an online journal BMJ Open..

It takes an average of 30 days for SARS-CoV-2, the virus responsible for COVID-19 infection, to clear the body from the first positive test, and an average of 36 days after first manifestation of symptoms. Because it is. .. And it warns researchers that it’s not yet known how infectious people are in the recovery phase.

In addition, the findings show that the rate of false-negative test results—people falsely reassure that the body is free of active (dropped) viruses-because they are relatively high (1/5) early in recovery. Indicates that you are at risk. It spreads without knowing it.

Accurately assessing the time it takes for the body to clear SARS-CoV-2 is the key to reducing the risk of ongoing infection and minimizing the duration of quarantine in asymptomatic patients. The researchers say.

To investigate this further, they tracked the progress of 4538 residents of the Province of Reggio Emilia in the Emilia-Romagna region of Italy. All were virus positive from February 26th to April 22nd this year.

Italy was the first Western country to be affected by COVID-19. By mid-April 2020, the number of cases and associated deaths was the third largest in the world. Emilia Romagna was one of the three in the country Coronavirus Local hotspots.

Due to lack of data, 4480 people were included in the preliminary analysis. 1259 achieved viral clearance as measured by at least one negative swab test after the first positive test, resulting in 428 deaths. The average time to virus clearance was 31 days from the first positive swab test.

The rate of viral clearance was then investigated in 1162 of the original 4480 individuals who had sufficient time since the first positive swab (at least 30 days). Each surviving patient was retested on average 3 times. About 15 days after the first positive swab. After the second 14 days. And 9 days after 3 days.

Viral clearance was detected in 704 (60.5%) and was found in less than 79% retested after the first negative swab (436/554). This suggests one false negative rate for every five negative test results.

The average time to virus clearance for this group was 30 days after the first positive swab and 36 days after the onset of symptoms, but it took a little longer depending on age and severity. infection..

Based on their findings, researchers found that retesting almost 14 days after swab positivity gave the same results, with a relatively high rate of false-negative results even when retested up to 3 weeks later. Suggests that.

Researchers warn that their data point to a long-lived shedding of the virus. [30 days from the start of symptoms] Or, you should do at least one follow-up test before you quarantine. “

Point out that they were previously published Experimental research Those in convalescence are likely to be positive but not infected, suggesting that WHO should be recommended for isolation periods of up to 13 days and asymptomatic isolation periods of up to 10 days. I am.

“But the evidence for risk of infection during convalescence is [swab test] Is weak and current serological data provide no additional insight. Moreover, the current epidemiological evidence of transmission is influenced by how quarantine has been managed so far,” the researchers warned.