Enlarge /. Even after the national ban has ended, Italy will still block residential buildings if there are clusters of cases.
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Italy was one of the earliest affected countries when the COVID-19 pandemic spread beyond its origins in China, and the country struggled with a surge in cases that threatened to overwhelm its health services. Italy, however, became a success story when an aggressive barrier reversed its curve and new daily falls fell from a high of over 6,000 to a constant current of around 300. Compared to a number of other industrialized democracies, this has been an important success factor.
A team of researchers, most of whom are based in Italy, are now investigating the spread of the pandemic and the effects of control measures more closely. The researchers have caused the majority of the population of a small town to agree to tests before and after Italy's lockdown to gain insight into the behavior of the virus and changes during the lockdown.
At the beginning
The place in question is called Vo & # 39;, a small town in northern Italy near Padua and Verona. Vo & # 39; has a population of just over 3,000, and most of them (86 percent) agreed to participate in the study. At the end of February this year, when Italy entered the ban, all willing participants gave samples that were tested for the presence of SARS-CoV-2. Two weeks later, as Italy was preparing to get out of its suspension, the participants were interviewed again. In the meantime, all health problems and contacts were examined so that contact networks could also be tracked.
This before-and-after sampling allowed researchers to estimate how the virus had spread before blocking, how it spread during spread, and to track the development of symptoms in those infected. The information gathered by the team should therefore provide the information we need to develop more effective control measures and build better epidemiological models.
Italy reported its first known case of the corona virus on February 20 of this year, but the virus had previously been clearly in circulation. At the time of the first survey on February 24, 73 people were already infected in Vo, which corresponds to 2.6 percent of the participants. In the following weeks, 40 percent of the infected people developed no symptoms, which is consistent with a large number of studies that indicate a high rate of asymptomatic infections. The researchers quantified the amount of virus present, but saw no difference between those with and without symptoms.
In the course of the study, 16 percent of those infected ended up in the hospital. While most of them were over 60, there were people under 60 who had severe cases.
Older people developed infection almost three times more often, which is in line with what has been observed elsewhere. This is in striking contrast to children. Of the 234 children in the study population, none were infected with the virus, although some of them shared a house with an infected person.
In between and after
Slightly more than half of the people who the researchers found infected at the start of the survey had no detectable virus two weeks later, indicating that they had cleared the infection. The researchers estimate that the virus took about nine days to average, with younger people and those with symptoms getting rid of the virus faster. For those who develop symptoms, the amount of virus present appeared to peak on the day the symptoms first appeared.
The poll at the end of the block shows how effective Italy's political approach was. At that time there were only 29 cases of active infection, or 1.2 percent of the total population. More importantly, only eight of them were new infections. The authors estimate that each infected person transmitted the virus to an average of 2.5 additional people before blocking. During the closure, this level fell to 0.4, a rate at which the pandemic cannot be sustained.
Two of these eight newly infected people appear to have taken the virus from an asymptomatic carrier, which supports the idea that infectivity is not closely related to symptoms. The authors also estimate that humans are usually able to transmit the virus for about four to seven days throughout the course of their infection.
These numbers should not be considered final. There are undoubtedly some details of social interactions within Vo & # 39; that do not apply elsewhere. But it's also probably much closer to "normal" interactions than in other cases where we've seen this kind of detailed survey of populations like cruise ships. And with enough examples like Vo & # 39; we can get a clearer picture of what the typical behavior of the virus looks like.
Equally critical, the data clearly shows that we can use political decisions to control a potentially catastrophic pandemic without waiting for a vaccine or fully effective treatment. As the authors put it: "The experience of Vo & # 39; shows that despite the silent and widespread transmission of SARS-CoV-2, the transmission can be controlled and a model for the systematic suppression of virus outbreaks under similar epidemiological and demographic Represents conditions. " While the blocking has clearly not eliminated infections in Italy, it has contributed to the fact that the incidence is so low that less stringent restrictions on contact tracking seem to limit the spread of the pandemic in Italy.
Nature, 2020. DOI: 10.1038 / s41586-020-2488-1 (Via DOIs).