Elisabetta De Cao and Alessia Melegaro (Dondena Centre), with Emilio Zagheni (Max Planck Institute) and Piero Manfredi (Università di Pisa) presented The Relative Importance of Frequency of Contacts and Time of Exposure for The Spread Of Directly Transmitted Infections ad Alp-Pop 2012. The Alpine Population Conference (La Thuile, 15-18 gennaio 2012).
Abstract: The impact of public health interventions against infectious diseases critically depends on how individuals mix and the social context in which this mixing occurs. The availability of POLYMOD contact data has initiated the understanding of the relationship between individual interactions and close-contact childhood infection processes even if there are still unsolved problem such as necessary to assess the overall uncertainty in the estimates. A new model is proposed here that integrates di_erent available data sources on social activities and contact patterns (Time Use Data and POLYMOD data), and estimate mixing matrices that more thoroughly describe the relevant social structure for infections spread assuming that potentially infectious contacts are proportional to self-reported number of social contacts and time of exposure in social activities. Mixing matrix and transmission-model parameters are jointly estimated by using the Bayesian melding approach to take into account the overall uncertainty. Due to the availability of Italian data on contact pattern, time use data from early ages, and data on VZV and Parvovirus B19, this setting is used as an example. About 23% of the time of exposure per contact results suitable for VZV infection transmission whereas it is only around 1% for B19 infection. The R0 for VZV is around 6, while for B19 is around 3. Moreover, physical contacts appear to be critical when considering respiratory infections.