Research, 'coronavirus was in Lombardy since January 1st'

The coronavirus began to circulate in Lombardy from January 1st and continued to do so in a submerged way for over a month and a half before the diagnosis of patient 1 of Codogno, which took place on February 20. This is what emerges from the analysis published on the ArXiv website and conducted by 14 research centers, with the coordination of the General Directorate of Health of the Lombardy Region. "The epidemic in Italy has remained unknown for weeks," writes Nature magazine today, commenting on the research on its website.

"The epidemic in Italy began long before February 20, 2020. By the time the first case of Covid-19 was identified, it had already spread to many municipalities in southern Lombardy," reads the article. "It is an extremely interesting work that reconstructs the prehistory of the coronavirus in Italy", commented the physicist Giorgio Parisi, of the Sapienza University of Rome. From the research, he continued, it also emerges that at the beginning the symptomatic cases were 80%, against 5% of asymptomatic and 15% of unclear cases, perhaps with symptoms so light as not to give the security of the infection.

The authors of the research reconstructed the origin of the epidemic by analyzing the data relating to 5,830 cases confirmed in the laboratories of Lombardy, for which the data relating to the appearance of symptoms had also been reported. Then we proceeded backwards, reconstructing the chain of contacts further and further back in time. Thus the sporadic cases that appeared in the region from 1st to 29th January and then the most frequent cases from 30th January to 19th February were identified, with a peak of over 60 occurred on 18th February. Two days later, on March 20, the epidemic came out, with the identification of patient 1 in Codogno.

The researchers also estimated that the reproduction rate was 3.1 initially, meaning that each person with the infection could infect 3.1, and began to decrease after February 20. Furthermore, in the initial phase, the epidemic spread exponentially, with an average doubling of cases every three days in Bergamo (3.5 days), Codogno (3.4 cases) and Cremona (2.6).