How is the contagion going in Umbria? The Rt indicator, temporary outbreaks and data explained well


With the new report published by the Higher Institute of Health (ISS), theUmbria has returned below the threshold for an important indicator that measures the expansion of contagions for COVID-19. The first version of the institute’s weekly monitoring had aroused some attention, in which the region of central Italy was among the only three (together with Lombardy and Molise) classified as “moderate”, while the other 18 autonomous regions and provinces had been included – based on a series of criteria – among those with a “low” profile.

In Umbria, in fact, the weekly classification had gone from low to moderate for “an increase in the number of cases” and an Rt index greater than one. The Rt indicator (net reproduction index) expresses the average number of new infections generated by a patient on a certain date, ed it is a fundamental measure to understand the direction of the epidemic – that is, whether it is speeding up or slowing down. If it is greater than one, it means that each patient tends to infect, on average, more than another person, which means that the expansion of the epidemic is accelerating. Otherwise, when the RT is less than one, it “suffocates” like a fire from which the air is removed. All this, “in a context still with a reduced number of reported cases and which therefore does not raise a particular alert”.

Subsequently, however, this indicator returned below the unit, indicating that precisely as the first analyzes suggested, it had been a temporary outbreak and fortunately soon brought back under control. It is also a useful lesson on how to interpret this kind of measurement. It should not be taken literally, in the sense that there is no need to be alarmed if a single week or a single region temporarily has values ​​greater than one. However, when it remains at the top for some time – as happened in the most acute phases of the epidemic in recent months – it becomes an important alarm bell. Ignored too long, it can lead to a contagion that grows as happened in Lombardy.

Given the information available, this is perhaps the most accurate measure we have available to get an idea of ​​how things are going. Unfortunately, however, it also has an important limit: “since the diagnosis of SARS-CoV-2 coronavirus infection [ovvero il virus che causa la malattia che abbiamo chiamato COVID-19] it can also occur two or three weeks after infection due to the incubation time of the disease (up to 14 days) and the time between the onset of symptoms, the search for medical assistance and the completion of laboratory tests, the Rt value can only be correctly estimated with a delay of 15 days“. The numbers published by the ISS on May 22, for example, are to be considered complete only until May 3, that is, before the easing of emergency measures against the disease began.

This is the first reason why it is wise to wait at least a few weeks before drawing conclusions. The second is that a phenomenon of this kind literally concerns the behavior of tens and tens of millions of people, and has such inertia that it takes time to change direction in any direction. Certainly it is not that until May 4 all Italians (or for this reason the inhabitants of Umbria) had remained closed in the house, and then went out en masse as soon as possible.

According to data collected by a study by ISI Foundation and University of Turin on people mobility, for example, in Umbria as elsewhere people contacts certainly went up again after May 4th. But they have not yet returned to where they were before the epidemic began. The same suggests the data of Apple made from their cell phones, which show that as of May 26, car mobility in the region is still much lower than in the pre-closure phase.

Plus after two months of lockdown there are far fewer cases in circulation than before, and therefore it will take time to start seeing a new increase in infections – although of course we all hope that this will not happen.

In more detail, as reported on Infodata Cristina Da Rold, the Umbria region created a page dedicated to the emergency where you can find the latest updates.

TOOn May 27, there were currently 46 positive people compared to 49 on the previous day – therefore a 6% drop. The current cases are concentrated in the northern and southern part of the region, with in particular several positives in Terni. The town of San Gemini, 5 thousand inhabitants in the province of Terni, is the one with the highest positive rate per thousand inhabitants, with 0.81 cases compared to the reference population.

(Source: Umbria Region)

On the whole, we still read, lhe region had 1,431 cases which could be confirmed through a test, 1,310 healed and 75 deaths. The number of cases does not include all those who have contracted the disease, but only those who have been identified by swabs. However, it is entirely plausible that several other people (perhaps completely asymptomatic) have fallen ill without even realizing it, or that not all suspects have been tested.

So far 66,202 swabs have been conducted in Umbria. According to the civil protection data, at the same time, the cases tested were a thread less than 47 thousand. The difference from these numbers depends on the fact that the same person, for various reasons, can be tested even more than once. UA way to understand if a region is conducting many or few tests is to calculate how many cases have been analyzed for each death. It is a useful measure since the areas where the epidemic is more extensive must, to contain it, make more swabs than others where the situation is less serious. According to this metric, Umbria is the third Italian region, with 626 tested cases conducted for each death. In Lombardy, to make a comparison, we find the opposite situation and for each death just 26 people have been tested instead.

However at the moment in Umbria there are also 481 people in isolationor (7% more than the day before when they had been 450), while 22,614 have come out of this condition. There are 15 hospitalized, one more than on 26 May, two of which are in intensive care. The site also offers a very useful overview common by municipality and even hospital by hospital, from which it can be verified that all patients in the region were hospitalized in two different structures, respectively at Terni and Todi (Perugia).

According to the ISS weekly report, updated on May 21, the regional reference laboratories have diagnosed 1,425 infections with a median age of 54 years. This means that there were as many sick people younger than that age, as there were older ones.

Until now, Umbria, like many other central-southern regions, has been spared the worst consequences of the epidemic, as has happened in Lombardy. But this does not mean that there were no victims. A report created by ISS and Istat analyzed the mortality data of 87% of Italian municipalities, finding that in March deaths in Umbria increased by7% compared to the average of the four years previous in the same period. The situation was similar both in the province of Perugia and in that of Terni, with values ​​in both cases not too far from that percentage value.

In the case of Perugia we even have even more detailed information about the city alone, which comes from the daily mortality monitoring system (SISMG). In the regional capital, authors and authors note, 294 deaths occurred against the expected 263 on 28 April, with an increase of 12% over a period of two months. This type of calculation is, according to experts, the best way to try to understand how many COVID-19 deaths have really been.

Counting only the cases reported by the civil protection actually leads to an underestimation of the real values ​​- as for those who died without having been tested for the disease.

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