Study in a complete Italian town finds that 40% virus cases were asymptomatic

Archive image of members of the Italian Army wearing face masks while checking a driver’s permission to enter the Turano Lodigiano red light area, closed due to the coronavirus outbreak in northern Italy, in Turano Lodigiano, Italy. February 26, 2020. REUTERS / Yara Nardi / ArchiveLONDON, Jun 30 (Reuters) – A study of coronavirus infections that covered almost the entire population of Vò, a confined town in northern Italy, found that 40% of the infections showed no symptoms, suggesting that asymptomatic cases are important in the spread of the pandemic. The study, led by a scientist at the University of Padua and Imperial College London, also provided evidence that massive tests combined with case isolation and community confinement can quickly stop local outbreaks. “Despite widespread and ‘silent’ transmission, the disease can be controlled,” said Andrea Crisanti, a virologist and academic from Padua and Imperial who co-directed the work. “Checking all citizens, whether they have symptoms or not, provides a way to (…) prevent outbreaks from spiraling out of control.” Crisanti has become a sort of celebrity in Italy for advising mass testing before it became an official guide for the World Health Organization. Vò, which has a population of almost 3,200, was immediately quarantined for 14 days after suffering the first death from Italy’s COVID-19 on February 21. During that fortnight, researchers tested the population for the presence of SARS-CoV-2, the coronavirus that causes COVID-19. An analysis of the results, published Monday in the journal Nature, showed that 2.6% of the Vò population -73 people- was positive at the beginning of the confinement. After two weeks, only 29 people tested positive. Both times, 40% of the positive cases showed no symptoms. But since all detected cases of the virus – with or without symptoms – were in quarantine, that helped slow the progression of the disease, effectively suppressing it in a few weeks, the researchers said. Crisanti said that the success of the massive tests in Vò also guided general public health policy in the Veneto region, where it had had “a tremendous impact on the course of the epidemic” there relative to other regions. Report by Kate Kelland; Edited in Spanish by Janisse Huambachano Our Standards: The Thomson Reuters Principles