Robbio, Italy: 70% of seropositive were asymptomatic

The first town of its size in Europe to offer free blood antibody testing.

Blood sampling in Robbio. Photo: Miguel Medina / AFP.

In early April the town of Robbio, Italy became the first town of its size in Europe to do a serosurvey open to its entire population.

Mayor Roberto Francese invited all town citizens to have a blood samples taken, by appointment, at the municipal Palasport, sports stadium. Those under self-quarantine were visited at home and blood drawn there.

The samples were assayed by a private laboratory, Omnilab, in Milan. The reagents and protocols for the test were developed jointly by the Universities of Padua and Verona.

Numbers released as of 9 April 2020:
• 1,300 people tested of 6,000 in the town
• 11.5% seropositive
• 70% of seropositive were asymptomatic
• 90% were not PCR positive by pharyngeal swab

The town had an official case count by PCR testing of 23.

Language notes:

The Italians simply call the seropositive the “immune.” None of the usual caveats and qualifications there!

They use an interesting term “band immunity” (l’immunità per fasce):

If there was a serum-prevalence in certain categories, for example, the data could be extended nationwide, thus allowing to apply ‘band immunity’, a more sophisticated version of ‘herd immunity.’

Robbio, Italy on the map.

Robbio is a city and commune in the Province of Pavia in the Italian region Lombardy, located about 50 km southwest of Milan and about 45 km west of Pavia. It is part of Lomellina traditional region.

You can follow the COVID aB Tracking blog on Twitter @Will_Bates_sci

Will Bates writes about science, technology, and business. His journalism has appeared in the New York Times, the Wall Street Journal, and numerous magazines.