FILE PHOTO: Members of the Italian Army wearing protective face masks are checking a driver's permission to enter the red zone of Turano Lodigiano, which was closed due to a coronavirus outbreak in northern Italy on February 26, 2020 in Turano Lodigiano, Italy. REUTERS / Yara Nardi / File Photo
LONDON (Reuters) – A study of coronavirus infections, involving almost everyone in the quarantined northern Italian city of Vò, showed that 40% of the cases showed no symptoms – suggesting that asymptomatic cases are important for the spread of the pandemic are.
The study, conducted by a scientist from Padua University in Italy and Imperial College London, also provided evidence that mass testing combined with case isolation and community locks can quickly stop local outbreaks.
"Despite" silent "and widespread transmission, the disease can be controlled," said Andrea Crisanti, professor at Padua and Imperial, who headed the work together. "Checking all citizens for symptoms or not is one way to … prevent outbreaks from getting out of control."
Crisanti has become famous in Italy for advocating widespread testing long before it became the official guidance of the World Health Organization.
Vò, with nearly 3,200 residents, was immediately quarantined for 14 days after Italy's first COVID-19 death on February 21.
During that fortnight, researchers tested most of the population for SARS-CoV-2, the coronavirus that causes COVID-19.
An analysis of the results, published in the journal Nature on Monday, showed that 2.6% of the population of Vo – or 73 people – were positive at the beginning of the quarantine. After two weeks, only 29 people were positive.
At both times, around 40% of the positive cases showed no symptoms. However, since all coronavirus cases found – whether symptomatic or not – were quarantined, the researchers helped slow the spread of the disease and effectively suppress it in a few weeks.
Crisanti said the success of Vo's mass tests has also led to a wider public health policy across the Veneto region, where it has "had a huge impact on the course of the epidemic" compared to other regions.
Reporting by Kate Kelland; Edited by Kevin Liffey
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