London, July 1 : Researchers have revealed that more than 40 per cent of coronavirus cases in an Italian town called Vo were asymptomatic. The study, published in Nature, suggests asymptomatic or pre-symptomatic people are an important factor in the transmission of Covid-19.
"Our research shows that testing of all citizens, whether or not they have symptoms, provides a way to manage the spread of disease and prevent outbreaks from getting out of hand," said researcher Andrea Crisanti from the University of Padua in Italy.
The town of Vo, with a population of nearly 3,200 people, experienced Italy's first Covid-19 death on February 21. The town was put into immediate quarantine for 14 days.
During this time, researchers tested most of the population for infection of SARS-CoV-2, the virus that causes Covid-19, both at the start of the lockdown (86 per cent tested) and after two weeks (72 per cent tested).
The testing revealed that at the start of the lockdown, 2.6 per cent of the population (73 people) were positive for SARS-CoV-2, while after a couple of weeks only 1.2 per cent (29 people) were positive.
At both times, around 40 per cent of the positive cases showed no symptoms (asymptomatic).
The results also show it took on average 9.3 days (range of 8-14 days) for the virus to be cleared from someone's body.
None of the children under ten years old in the study tested positive for COVID-19, despite several living with infected family members. This is in contrast to adults living with infected people, who were very likely to test positive.
As a result of the mass testing any positive cases, symptomatic or not, were quarantined, slowing the spread of the disease and effectively suppressing it in only a few short weeks, the researchers said.
"The VÃ² study demonstrates that the early identification of infection clusters and the timely isolation of symptomatic as well as asymptomatic infections can suppress transmission and curb an epidemic in its early phase," said study co-lead researcher Ilaria Dorigatti from the Imperial College London.
"This is particularly relevant today, given the current risk of new infection clusters and of the second wave of transmission," Dorigatti added.
According to the authors, there are still many open questions about the transmission of the SARS-CoV-2 virus, such as the role of children and the contribution of asymptomatic carriers to transmission.
"Finding answers to these questions is crucial to identifying targeted and sustainable control strategies to combat the spread of SARS-CoV-2 in Italy and around the world," they wrote.
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