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After 30 days from diagnosis, half of Covid-19 patients are still positive: Italian research
On average, it takes 30 days, starting with the first positive swab, to clean the coronavirus of the body. This was established by an Italian company, according to which it takes 36 days from the appearance of the first symptoms. In fact, experts have observed that half of patients remain infected for a month after the Covid-19 diagnosis.
The Italian Study was published in the BMJ Open magazine and was carried out 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.
Regarding the period in which the subject remains contagious from the time of diagnosis, the scope is still unclear.
Half-positive patients after 30 days: what changes
The study could have an impact on isolation times and strategy around tampons. Currently, the WHO recommends 13 days of isolation from the onset of Covid symptoms and 10 from the date of the positive swab in an asymptomatic person.
“In Italy, one of the study authors explained to Ansa, Francesco Venturelli of the Epidemiology Service of the Emilian health company – we adopted a stricter protocol which foresees the need to obtain two negative pads consecutively to get out of isolation ”.
However, “from the results of our study – added the epidemiologist – it is clear that approximately half of symptomatic patients remain positive 30 days after the first swab” and that therefore it is not very useful to repeat the tampon already after 2 or 3 weeks from diagnosis.
The experiment: the case of “false negatives”
In their experiment, epidemiologists monitored an initial group of 4538 residents in the province of Reggio Emilia (positive and symptomatic) and found that performing a second swab 2 or 3 weeks after the first one in most cases obtained a successful again.
Among those who test negative on a swab performed within the first 3 weeks of diagnosis, there is also a high risk of “False negative”, that is, the swab incorrectly indicates that there is no virus in the body.
The false negative rate, in the observed sample, is relatively high (1 case out of 5) in the first part of convalescence, potentially putting the subject at risk of ending isolation while remaining positive.
In the Italian case, where two consecutive negative smears are required, this risk is extremely low, but in other countries a false negative could occur. promote transmission unaware of the virus.
The conclusion reached by the experts is that “to reduce the number of false negatives and the number of necessary controls, do controls 4 weeks after the first swabin short, postponing the first check-up for symptomatic people in isolation could improve the efficacy and safety of the protocols ”.
VIRGILIO NEWS | 03-09-2020 07:10
Photo Source: Ansa
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