1

It's been mentioned in another answer that

In COVID-19, The University of Padua, Veneto Region and the Red Cross tested the population of Vò, Italy, 3300 people, to establish the natural history of the virus, the transmission dynamics and categories of risk. " they found >50 of those who tested positive to be asymptomatic” according to Professor Sergio Romagnani.

I'm aware that a Covid-19 prevalence study on the [entire population of the] Diamond Princess ship (3,711 passengers and crew) has been published in Eurosurveillance. Has this comparable (in size) study on an entire Italian town been published somewhere?

(I see a later issue of Eurosurveillance has a larger study on Lombardy, but it doesn't mention Vò specifically. Also, this latter issue has a 2nd study on the Diamond Princess.)

1

It took a while, but it has now been published in Nature:

"Suppression of a SARS-CoV-2 outbreak in the Italian municipality of Vo’"

by Enrico Lavezzo, Elisa Franchin, […]Andrea Crisanti, Nature (2020). Published: 30 June 2020

This seems to be the same content as the preprint linked and discussed by @Fizz in their answer.

Abstract

On 21 February 2020, a resident of the municipality of Vo’, a small town near Padua (Italy), died of pneumonia due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection1. This was the first coronavirus disease 19 (COVID-19)-related death detected in Italy since the detection of SARS-CoV-2 in the Chinese city of Wuhan, Hubei province2. In response, the regional authorities imposed the lockdown of the whole municipality for 14 days3. Here we collected information on the demography, clinical presentation, hospitalization, contact network and the presence of SARS-CoV-2 infection in nasopharyngeal swabs for 85.9% and 71.5% of the population of Vo’ at two consecutive time points. From the first survey, which was conducted around the time the town lockdown started, we found a prevalence of infection of 2.6% (95% confidence interval (CI): 2.1–3.3%). From the second survey, which was conducted at the end of the lockdown, we found a prevalence of 1.2% (95% CI: 0.8–1.8%). Notably, 42.5% (95% CI: 31.5–54.6%) of the confirmed SARS-CoV-2 infections detected across the two surveys were asymptomatic (that is, did not have symptoms at the time of swab testing and did not develop symptoms afterwards). The mean serial interval was 7.2 days (95% CI: 5.9–9.6). We found no statistically significant difference in the viral load of symptomatic versus asymptomatic infections (P = 0.62 and 0.74 for E and RdRp genes, respectively, exact Wilcoxon–Mann–Whitney test). This study sheds light on the frequency of asymptomatic SARS-CoV-2 infection, their infectivity (as measured by the viral load) and provides insights into its transmission dynamics and the efficacy of the implemented control measures.

2

As far I know, no. Only an open letter has been published so far:

https://corrierefiorentino.corriere.it/firenze/notizie/cronaca/20_marzo_15/dobbiamo-cambiare-rotta-ef23a500-669a-11ea-a40a-86d505f82a96.shtml

1

The data has also been discussed in this report

Sergio Romagnani, a professor of clinical immunology at the University of Florence, has reported how blanket testing in a completely isolated village of roughly 3000 people in northern Italy saw the number of people with covid-19 symptoms fall by over 90% within 10 days.

So by isolating those that were asymptomatic and testing positive to the virus, they dropped the symptomatic infection rate by 90%.

https://www.bmj.com/content/368/bmj.m1165

2
  • An Italian politician claimed literally 0% infection after lockdowns. Alas my question on that was closed on Skeptics, as if there was no data to answer it. skeptics.stackexchange.com/questions/46031/… – Fizz Mar 27 '20 at 23:06
  • It's a bit weird the BMJ sort-of credited Romagiany with this, when he was reporting on the study of Crisanti and Cassone, which certainly had put out a press release in English (March 19) by the time of BMJ piece (March 23) It's true that Romagnani wrote on this before (March 15, in Italian) – Fizz Mar 28 '20 at 0:57
0

In a Nature roundup, the following (mid April) draft paper has been highlighted as the main scientific publication on that town/survey:

https://www.medrxiv.org/content/10.1101/2020.04.17.20053157v1

On the 21st of February 2020 a resident of the municipality of Vo, a small town near Padua, died of pneumonia due to SARS-CoV-2 infection. This was the first COVID-19 death detected in Italy since the emergence of SARS-CoV-2 in the Chinese city of Wuhan, Hubei province. In response, the regional authorities imposed the lockdown of the whole municipality for 14 days. We collected information on the demography, clinical presentation, hospitalization, contact network and presence of SARS-CoV-2 infection in nasopharyngeal swabs for 85.9% and 71.5% of the population of Vo at two consecutive time points. On the first survey, which was conducted around the time the town lockdown started, we found a prevalence of infection of 2.6% (95% confidence interval (CI) 2.1-3.3%). On the second survey, which was conducted at the end of the lockdown, we found a prevalence of 1.2% (95% CI 0.8-1.8%). Notably, 43.2% (95% CI 32.2-54.7%) of the confirmed SARS-CoV-2 infections detected across the two surveys were asymptomatic. The mean serial interval was 6.9 days (95% CI 2.6-13.4). We found no statistically significant difference in the viral load (as measured by genome equivalents inferred from cycle threshold data) of symptomatic versus asymptomatic infections (p-values 0.6 and 0.2 for E and RdRp genes, respectively, Exact Wilcoxon-Mann-Whitney test). Contact tracing of the newly infected cases and transmission chain reconstruction revealed that most new infections in the second survey were infected in the community before the lockdown or from asymptomatic infections living in the same household. This study sheds new light on the frequency of asymptomatic SARS-CoV-2 infection and their infectivity (as measured by the viral load) and provides new insights into its transmission dynamics, the duration of viral load detectability and the efficacy of the implemented control measures.

The 43% asymptomatic is a bit less than what was reported from the Princess, but it overlaps it in the 95% CI 32.2-54.7%.


End or March answer, largely obsolete now, but leaving it for some press coverage:

Also March 20 coverage in the Guardian, which is of course not a science venue, but had even more details than even the BMJ coverage; the "opinion piece" in the Guardian was apparently written by the researchers/epidemiologists involved:

in the last two weeks, a promising pilot study here has produced results that may be instructive for other countries trying to control coronavirus. Beginning on 6 March , along with researchers at the University of Padua and the Red Cross, we tested all residents of Vò, a town of 3,000 inhabitants near Venice – including those who did not have symptoms. This allowed us to quarantine people before they showed signs of infection and stop the further spread of coronavirus. In this way, we eradicated coronavirus in under 14 days. [...]

Our experiment came to be by chance. The Italian authorities had a strong emotional reaction to news of the country’s first death – which was in Vò. The whole town was put into quarantine and every inhabitant was tested. The tests were processed by us at the University of Padua. [...]

In the first round of testing, 89 people tested positive. In the second round, the number had dropped to six, who remained in isolation. In this way, we managed to eradicate coronavirus from Vò, achieving a 100% recovery rate for those previously infected while recording no further cases of transmission.

Strong claims here. They also say/claim that

asymptomatic or quasi-symptomatic subjects represent a good 70% of all virus-infected people

referring to COVID-19.

About the authors, the Guardian notes:

Andrea Crisanti is professor of microbiology at the University of Padua; Antonio Cassone is a former director of the department of infectious diseases at the Italian institute of health.

I guess I now know whose publications to look at (in the future).

There's a longer interview with Crisanti on CBC.ca. An intersting bit:

I want to draw a comparison. If you remember the Diamond Princess. They started with few cases. They did the tests only to those [who] were symptomatic. So you develop a symptom, you test positive, you were taken out of the ship.

But day by day, cases, if you remember, they increased up to more than 700. So in this way, they couldn't stop the disease. That couldn't stop the disease in spite of the fact that they were isolated, they were kind of quarantined. And the reason why they couldn't stop it is because the ship was full of asymptomatic people that [were] spreading the virus.

Q: [When you started this in February], the protocol was that you tested people only if they … were returning from a foreign place, or from China, or if they had symptoms. ... You ignored that and went to everybody.

Yeah, we ignored that because we weren't convinced that the disease was transmitted only by symptomatic individuals. We found this quite implausible. And so this is the reason why we tested everybody.

3
  • So, even though they had the first death, the silver lining was that the whole town was then cleared of the virus. Now, they'll have to keep everyone out until the country is clear. – Graham Chiu Mar 28 '20 at 0:39
  • @GrahamChiu: it's a bit unclear what measures were taken exactly. I suspect they completely forbade people who tested positive, even if asymptomatic from leaving their homes. That's why I'm hoping for a more serious/peer-reviewed publication. Right now the press stories we have are a bit "fluffy", and it's also a bit odd that there's no expert [besides the authors'] commentary on these. – Fizz Mar 28 '20 at 0:42
  • 1
    the BMJ in my link says *All those with positive tests were quarantined. * – Graham Chiu Mar 28 '20 at 0:51

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.