More than 40% of people living in an Italian city, tested positive for Covid-19, had no sign of disease, according to a study published Tuesday highlighting the potential for the spread of the new coronavirus.
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This research shows the importance of mass tests and the isolation of virus carriers to contain sources of contamination (" clusters "), according to the authors whose work has appeared in the scientific journal Nature .
At the end of February, the first death in Italy was recorded in the town of Vo '(3200 inhabitants), near Padua (Veneto region, north of the country). The city was immediately placed in confinement for two weeks, during which researchers were able to carry out virological tests on more than 85% of the population. At the start of the quarantine, 2.3% of the inhabitants of Vo 'were infected against 1.2% at the end of confinement and 42.5% of the people tested positive had no symptoms at the time of the test or after. According to the authors, their study shows that the rapid isolation of the cases and the mass tests have effectively eliminated the virus from this small town.
Similar viral load
" Screening all citizens, whether or not they have symptoms, helps manage the spread of the disease and prevent epidemics from getting out of control, " says Andrea Crisanti, of the Department of Molecular Medicine at the University of Padua and the Department of Life Sciences at Imperial College London. “ Despite 'widespread' silent transmission, the disease can be controlled. "
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Asymptomatic carriers of the infection had similar viral loads to those who fell ill, suggesting that even without being sick themselves, they can spread the virus. " Even asymptomatic infections have the potential to contribute to transmission, " said Enrico Lavezzo, of the University of Padua, co-author of the study.
Unaware of their infection, asymptomatic people can, depending on their lifestyle and their profession, meet a large number of people without changing their behavior (including barrier gestures: mask, physical distance, hand hygiene). In addition, none of the children under the age of 10 tested positive, even though they were living with infected adults, the study found.
" The Vo 'study shows that the early identification of foci of infection and the rapid isolation of cases of infections with or without symptoms can eliminate transmission and stop an epidemic at its beginnings, " adds a researcher co-author. of the study, Ilaria Dorigatti, of the MRC Center for Global Infectious Disease Analysis of Imperial College London.