From La Stampa via Google Translate:
Coronavirus, Castiglione d’Adda is a case study: “70% of blood donors are positive”
All asymptomatic, but have antibodies. From their plasma an experimental cure for the sick
PUBLISHED ON April 02 2020
When Avis volunteers summoned them for blood donation, they were confident that they would find a high number of Covid positives19. Confirmation came from the results of tests and swabs: out of 60 citizens of Castiglione D’Adda, one of the municipalities in the former red area of Lodi, 40 tested positive without knowing it. All asymptomatic, escaped from official statistics: they came into contact with the disease, they did not develop it, but they have
This is different from Vo in Italy where in an earlier test of most everybody in town, only 3% came back positive. Vo suffered the first known coronavirus death in Italy, so it was immediately locked down and then given universal testing, which stopped the infections at about 3%.
Similarly, through two rounds of antibody testing in the Telluride, Colorado area (N=986) as of March 27, they have found 1% positive, 2 % grey area, and 97% negative.
Costantino Pesatori, the mayor of Castiglione D’Adda, one of those formerly quarantined towns, said that 47 people had died there since Feb. 21, compared with about 50 in all of 2019. He said that despite some of his residents having received a diagnosis of pneumonia, hospital officials “sent them home without testing them for coronavirus.”
This would suggest the total death rate in the town was about 10X its average monthly death rate.
By March 21, 62 deaths were officially attributed to the epidemic in this one town. And remember that official counts of coronavirus fatalities in Lombardy are probably understated because they typically haven’t counted those dying untested at home and in nursing facilities.
So if any place is approaching herd immunity, it ought to be these poor bastards in Castiglione D’Adda. They deserve some consolation.
iSteve commenter eugyppius speculates:
(WILD THEORY NOT PART OF TRANSLATION: People are donating blood in this town because it comes with a C19 test, and the “asymptomatics” are actually people who feel a bit sick, but you’re not supposed to donate blood when you’re sick, so they present themselves as not sick, and as surprised when the results come back positive for C19.)
Sounds plausible. That would suggest it’s not so much of a random sample as you might assume, but one tilted toward people who wanted a test and figured out away to get to the head of the testing queue.
There is a lot of excitement over this news article on Twitter, so we should keep in mind eugyppius’s observations before assuming it provides the One True Number for any calculation we might want to do.