This is indicated by the results of a new Italian study conducted by the Local Health Unit – IRCCS of Reggio Emilia on a large sample of symptomatic individuals who tested positive for the virus between February and April
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30 days: this is the average time that the body takes to eliminate the coronavirus. This is indicated by a new Italian study conducted by the Local Health Unit – IRCCS of Reggio Emilia on a large sample of symptomatic individuals who tested positive for the virus between February and April. From the research results, published in the journal BMJ Open, it also emerges that about half of patients are still positive for Covid-19 30 days after the first swab and 36 days after the onset of symptoms. However, doubts remain about the extent of the period in which the subject remains contagious from the moment of diagnosis. In fact, a positive swab does not indicate contagiousness, but simply signals the presence of genetic material of Sars-CoV-2 in the body.
The need for two negative swabs
To reduce the risk of contagion as much as possible, the World Health Organization (WHO) recommends 13 days of isolation from the onset of symptoms of the Covid-19 and 10 from the date of the positive swab in an asymptomatic person. “However, in Italy we adopt a more stringent protocol, which foresees the need to obtain two negative swabs consecutively to get out of the isolation”, explains Francesco Venturelli, author of the study and researcher of the Epidemiology Service of the Emilian healthcare company. “The results of our study show that about half of symptomatic patients are still positive 30 days after the first swab,” explains the expert. This implies that it is of little use to do a second swab two or three weeks after diagnosis.
The risk of “false negatives”
During their study, the epidemiologists monitored an initial group of 4,538 residents in the province of Reggio Emilia (positive and asymptomatic). When it came time for a second swab, two to three weeks after the first, most patients tested positive again. Experts also found that among those who test negative to a buffer performed in the first three weeks after diagnosis, the risk of a “false negative” is high (about one in five cases). In countries that, unlike Italy, do not require two negative swabs in a row, this could represent a big risk for the community. “In order to reduce the number of false negatives and the number of checks required, the checks could be started 4 weeks after the first swab, in short, postponing the first check in symptomatic people in isolation could improve the efficiency and safety of the protocols” , the study authors conclude.
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