From The Guardian:

Scientists say mass tests in Italian town have halted Covid-19 there

A study in Vò, which saw Italy’s first death, points to the danger of asymptomatic carriers

Lorenzo Tondo in Palermo @lorenzo_tondo Wed 18 Mar 2020 16.30 EDT

The small town of Vò, in northern Italy, where the first coronavirus death occurred in the country, has become a case study that demonstrates how scientists might neutralise the spread of Covid-19.

A scientific study, rolled out by the University of Padua, with the help of the Veneto Region and the Red Cross, consisted of testing all 3,300 inhabitants of the town, including asymptomatic people. The goal was to study the natural history of the virus, the transmission dynamics and the categories at risk.

The researchers explained they had tested the inhabitants twice and that the study led to the discovery of the decisive role in the spread of the coronavirus epidemic of asymptomatic people.

When the study began, on 6 March, there were at least 90 infected in Vò. For days now, there have been no new cases.

“We were able to contain the outbreak here, because we identified and eliminated the ‘submerged’ infections and isolated them,” Andrea Crisanti, an infections expert at Imperial College London, who took part in the Vò project, told the Financial Times. “That is what makes the difference.”

The research allowed for the identification of at least six asymptomatic people who tested positive for Covid-19. ‘‘If these people had not been discovered,” said the researchers, they would probably have unknowingly infected other inhabitants.

“The percentage of infected people, even if asymptomatic, in the population is very high,” wrote Sergio Romagnani, professor of clinical immunology at the University of Florence, in a letter to the authorities. “The isolation of asymptomatics is essential to be able to control the spread of the virus and the severity of the disease.”

That’s universal testing plus lockdown. A big question is what can we do without lockdown?