ROME – The Covid-19 epidemic in Italy shows signs of exponential growth, fueled by the increase in contacts typical of the summer season and by the spread of the Delta variant.
It is a different situation from that of July 2020, when the percentage of positive molecular tests was a quarter compared to the current one and admissions to intensive care were less than half, indicate the calculations of the mathematician Giovanni Sebastiani, of the Institute for Applications of the “Mauro Picone” Calculation of the National Research Council (Cnr-Iac).
“Our country is currently among the five in Europe that show such growth,” observes the expert, alongside the United Kingdom, the Netherlands, Greece and Denmark, albeit with fluctuations.
That the epidemic curve in Italy began to rise exponentially happened quickly, immediately after a phase of decline: a different situation from that of the end of September 2020, when the exponential growth was preceded by a long period of linear growth. “As expected – observes Sebastiani – the release of the restrictive measures at the end of April led, after five weeks, to an increase in cases at the provincial level due to the presence of localized outbreaks spread throughout the national territory”.
About three weeks ago, he continues, “the situation changed qualitatively, probably due to the increase in contacts linked to the typical activities of the summer season and, above all, to the spread of the Delta variant”.
According to the expert, “the absence of the obligation to wear the mask outdoors clearly favors the spread, but it cannot be considered the cause of the transition to the exponential phase, as it did for the start of educational activities in mid-September 2020 : the usual two canonical weeks are needed for its effects to manifest ».
The data indicate that “in the last 21 days there is an exponential growth with a doubling time of the increases between 6 and 7 days in the percentage of molecular test positives on the cumulative data of the 14 autonomous regions-provinces, which provide the positives separately to the molecular and to the unsanitary “. Also in the last 21 days “we observe an exponential growth with a doubling time of the increases between 5 and 6 days in the percentage of positives to both types of tests. For a more reliable estimate of the numerical value of the doubling times we have to wait at least another 6 days ».
Comparing with the situation in mid-July 2020, it emerges that the current percentage of molecular test positives, equal to 2%, is quadruple compared to that recorded in mid-July 2020, when it was 0.5%. On the other hand, the average value of deaths is comparable compared to a year ago, while patients hospitalized in intensive care units more than doubled. “The current one and that of last year – observes the expert – are in any case situations in which factors of different types weigh, starting from the vaccination campaign”.
The data processed by Sebastiani indicate that the percentage of molecular test positives is currently equal to 2%, in an exponential growth phase with a doubling time of the increases of about 6 days, while in mid-July last year it was in the phase of stasis and equal to 0.5%. As regards the number of patients admitted to intensive care, the average of the last seven days is 160; in the corresponding period of last year the average number of patients was 64.
