This study shows the importance of massive diagnostic tests and the isolation of virus carriers to contain the sources of contagion, according to the authors of the research, published in the scientific journal Nature.

In late February, the first death from the virus was recorded in Italy in the city of Vo '(3,200 inhabitants), near Padua, in the north of the peninsula. A two-week confinement was immediately imposed, during which scientists were able to virologically test more than 85% of the population.

At the beginning of the quarantine, 2.3% of Vo 'neighbors were infected, compared to 1.2% at the end of the confinement, and 42.5% of the people who tested positive had no symptoms at the time of the test, nor after.

"The diagnosis of all citizens, whether or not they present symptoms, allows managing the spread of the disease and preventing epidemics from being uncontrollable", according to Andrea Crisanti, from the Department of Molecular Medicine at the University of Padua and from the Department of Sciences at the Imperial College London.

"Even asymptomatic infections have the potential to contribute to transmission," insists Enrico Lavezzo of the University of Padua, co-author of the study.

Unaware of their infection, people without symptoms can be in contact with many people, without thinking about the barrier gestures that limit contagion, for example.

The study also indicates that children under the age of 10 did not test positive, even if they lived with infected adults.