Demographic science aids in understanding the spread and fatality rates of COVID-19

Jennifer Beam Dowd; Valentina Rotondi; Liliana Adriano; David M Brazel; Per Block; Xuejie Ding; Yan Liu; Melinda C Mills

A stylized example from social network theory can be helpful in explaining why intergenerational interactions, co-residence, and commuting patterns might have played a role in the spread of the COVID-19 infection to the older population in Italy. Individuals' social networks are generally composed of people similar in age. The population structure of contact can be represented as age-homogeneous communities that have low contact between groups. If the initial infections in northern Italy were younger people commuting to cities and having plausibly international contacts, a crucial determinant of risk for the elderly is their network distance to these younger sources, i.e. how many intermediaries need to be infected until they are reached. Network science showed that even relatively few connections between communities can lead to a stark reduction in average network distances; the so-called small world phenomenon 5 . Such community "connecting" individuals might be those young people around Milan that work in the city but reside in the most hard-hit villages in the surrounding with their parents and grandparents. Thus, intergenerational co-residence may have accelerated the outbreak by creating intercommunity connections that increase the proximity of elderly to the initial cases, an area for further study. . CC-BY 4.0 International license It is made available under a author/funder, who has granted medRxiv a license to display the preprint in perpetuity.