The extensive circulation of Sars-CoV-2 among the elderly in Italy during the first wave of the pandemic would not have been caused by the strength of inter-generational ties within families, but rather by the greater number of daily encounters with people of all ages, compared with other European countries like Germany and the United Kingdom
In Italy, during the first wave of the Covid-19 epidemic, the speed of Sars-CoV-2 as well as the level of lethality of the disease were higher than in other European countries. Many scholars have tried to explain this phenomenon by pointing out that in Italian society there are very close family ties, with grandparents, parents, children and grandchildren who often live together or at least see each other very often: a characteristic that would have contributed to the rapid spread of the virus among the elderly.
But a new study published in PLOS ONE and conducted by scholars from the universities of Trento, Sorbonne and Bologna now suggests a different explanation: what accelerated the spread of COVID-19 in Italy were not inter-generational contacts, but rather the fact that, on average, Italians have more face-to-face contacts with people of any age on a daily basis than populations in other countries such as Germany or the United Kingdom.
"The age structure of the population alone is not sufficient to explain the differences observed between Italy and other European countries", explains Marco Albertini, professor of the Department of Political and Social Sciences of the University of Bologna, one of the authors of the study. "The results of our study show, however, that more than the links between generations within Italian families, it is the specific characteristics of social networks that have played an important role in increasing the rate of spread of the virus".
To analyze the problem and identify the most relevant factors in the spread of the coronavirus (potentially), the scholars used a variety of simulation methods combined with real data on the characteristics of in-person social contacts.
The analysis examines, in particular, the characteristics of social networks in three countries: Italy, Germany and the United Kingdom.
"We specifically examined the role of three aspects of social networks," explains Lucas Sage, PhD student at the universities of Trento and the Sorbonne, first author of the study. "Degree distribution, or how many face-to-face contacts people have on average in the three different countries; age-mixing, or the age differences of the people you meet; clustering, or the tendency to share the same contacts in social networks".
By comparing these different aspects with data from Italy, Germany and the United Kingdom, the results of the simulations showed that age differences among people have a very low impact, while the overall number of face-to-face contacts determines a greater spread of the infection.
As for the Italian case, these results indicate that it is not the specific characteristics of family ties, but rather more generally the high level of sociability of the population that explains the higher speed of the coronavirus.
"An important consequence of these results is that contagion containment measures designed to reduce contacts between young and old people would not be particularly effective", concludes Stefani Scherer, professor of the University of Trento, one of the authors of the study. "More than the vertical contacts between age groups, it is in fact the number of face-to-face contacts in the general population that plays a role in the spread of the virus among the elderly".
The study was published in PLOS ONE with the title "The spreading of SASR-CoV-2: Interage contacts and networks degree distribution". The authors are Lucas Sage of the Department of Sociology and Social Research of the University of Trento and Sorbonne Université (France), Stefani Scherer of the Department of Sociology and Social Research of the University of Trento, and Marco Albertini, professor of the Department of Political and Social Sciences of the University of Bologna.