The physicist of the University of Trento: The descent of the contagions of the Omicron variant will probably be rapid, but the Delta variant could regain strength. This can be understood from the trend of the Rt index
With over two and a half million positives (of which about 19 thousand hospitalized and 1,700 in intensive care) and a Rt rapidly falling below 1.3 (number of people who can be infected by an infected individual), Italy could be close to the peak of the fourth wave. The rate of growth of the infections, a violent exponential trend when it appeared variante Omicron (December 23), down today. In countries like Italy and Greece we are getting very close to the peak and very likely that it will arrive in Europe sooner than expected, i.e. within 2-3 weeks, said the director of WHO Europe (World Health Organization), Hans Kluge . But in any case, he added, there is no escape from Omicron and we expect that at any time in the coming months, 40 out of 53 European countries will experience high stress on hospitalization and intensive care, considering the number of unvaccinated. The forecast should not apply to Italy, where 86.7% of the population over 12 completed the immunization cycle.
Roberto Battiston, full professor of Experimental Physics at the University of Trento and coordinator of the Observatory of epidemiological data which works in collaboration with the National Agency for Regional Health Services (Agenas), when will we see a marked decrease in cases?
We can make some considerations based on what has been observed in South Africa and Great Britain, the first countries to be “invaded” by Omicron: in the face of a very rapid growth in infections, an equally fast descent has occurred. In England, the increase started at the beginning of December, with us around Christmas. So we are 20 days behind the English situation, but we are already seeing the first signs of a possible slowdown. Even in other European countries, such as Spain, Portugal and even France, a decline is beginning to be seen. It should be noted that France with Omicron has exceeded 300 thousand infections a day.
How is the arrival of the peak calculated?
The data we are talking about is not that of new infections, but the total number of infected people present at a given moment, obtained by subtracting, day by day, that of the healed from the quota. The peak is exceeded when the number of healed exceeds that of new infections. Unfortunately, there are objective elements of uncertainty in this calculation. First: how reliable is the number of newly infected? Many positives are asymptomatic or paucisymptomatic and some opt for do-it-yourself tampons, staying at home but without reporting their situation to the ASL. Second: how reliable is the number of those healed? Since the beginning of the pandemic, the count of those who have overcome the infection has been considered “less important” in the management of the health emergency. We have to to deal with what we have.
How could the Rt parameter change in the next few days?
From Christmas onwards there has been a very rapid exponential growth, with a doubling time of cases which dropped to 5 days. We were saved thanks to vaccines, given that no generalized lockdowns were imposed: after having exceeded 200 thousand daily infections in a few days, the real risk was to quickly double these numbers. Luckily it didn’t happen. If Omicron is really losing strength, we will see in the next few days (excluding Monday, due to the weekend effect) a decrease in the new daily infected. To understand the epidemic trend, the Rt parameter is very important but must be calculated on the entire Italian population, not only on hospitalizations. Now about 1.3, rapidly descending. If, as it seems, Omicron-dominated Rt we have a further drop, probably below 1: the total number of infected will start to drop and we will see Omicron disappear. The value that Rt will reach will also depend on the fraction of Delta infections (which on January 3 was still at 20%), and we will be able to understand to what extent the measures implemented since the end of October are today effective in containing the Delta variant, which contributes significantly to severe cases and deaths in the unvaccinated, but fortunately responds well to vaccines.
How long will it take to understand the progress of the pandemic?
About a week: if the RT has dropped below 1 it means that the peak has been exceeded and we are in a bending phase. Of course, these predictions are never perfect, because there are many variables involved and not all of them can be measured in advance. There are also regional differences, which in some cases bode well: in Umbria, for example, Rt is falling below 1.1 and the active infection curve is showing its maximum.
January 18, 2022 (change January 18, 2022 | 14:09)
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