Blood tests have begun in the region around Rome to allow authorities to gauge how many people have been exposed to the coronavirus since the epidemic struck Italy.
More data will help to map out how the virus has travelled through the population, as the country begins to emerge from the health crisis that has killed nearly 30,000 of its citizens.
Over the following few days, the region of Lazio -- of which Rome is the capital -- will perform some 150,000 blood tests on health workers and police, those assumed to be most exposed to the virus.
Such tests have already begun in other regions, especially Lombardy in Italy's north which has been hardest hit by the coronavirus.
Sergio Bernardini, a professor in biochemistry and director of the lab at Rome's Tor Vergata hospital, said the large-scale screening efforts will produce a closer estimate of the number of people who have been infected with the virus.
"In reality, they're probably much more numerous, eight to ten times more than the figures we have today," Bernardini told AFP.
The tests, which require just a finger prick of blood, look for the presence of antibodies indicating that the person has been exposed to the virus at some point. The hope is that the person has developed immunity to the virus, although that is not guaranteed.
A positive result "does not mean that you are protected, it is not a license to return to normal daily life," Bernardini cautioned.
"It's absolutely necessary to continue using ... masks, which are still the most important thing, even more important than knowing if you have antibodies," he said.
The blood tests differ from the more common swab tests, which check molecules from nasal secretions to know whether a person currently has the virus.
Although the blood tests can help determine how many people may be immune, and how many have never been exposed to the virus, there are pitfalls, experts warn.
A person who has developed antibodies can still carry traces of the virus and be contagious. Moreover, it is not understood how long immunity to coronavirus lasts, meaning there is a risk those deemed "immune" could be re-infected and pass along the virus to others.
© 2020 AFP