The relative importance of frequency of contacts and duration of exposure for the spread of directly transmitted infections.
The recent availability of survey data on social contact patterns has made possible important advances in the understanding of the social determinants of the spread of close-contact infections, and of the importance of long-lasting contacts for effective transmission to occur. Still, little is known about the relationship between two of the most critical identified factors (frequency of contacts and duration of exposure) and how this relationship applies to different types of infections. By integrating data from two independently collected social surveys (Polymod and time use), we propose a model that combines these two transmission determinants into a new epidemiologically relevant measure of contacts: the number of "suitable" contacts, which is the number of contacts that involve a sufficiently long exposure time to allow for transmission. The validity of this new epidemiological measure is tested against Italian serological data for varicella and parvovirus-B19, with uncertainty evaluated using the Bayesian melding technique. The model performs quite well, indicating that the interplay between time of exposure and contacts is critical for varicella transmission, while for B19 it is the duration of exposure that matters for transmission.
Department of Economics, Econometrics and Finance, University of Groningen, Nettelbosje 2, 9747 AE Groningen, The Netherlands e.de.cao@rug.nl.
Elisabetta
E
De Cao
Department of Sociology, Powdermaker Hall 252EE, Queens College, City University of New York, New York 11367, USA.
Emilio
E
Zagheni
Facoltà di Economia, Università di Pisa, Via Ridolfi 10, I-56124 Pisa, Italy.
Piero
P
Manfredi
Department of Policy Analysis and Public Management and Dondena Centre for Research on Social Dynamics, Università Commerciale L. Bocconi, Via Roentgen 1, 20136 Milano, Italy.
Alessia
A
Melegaro
D001499:Bayes Theorem; D002644:Chickenpox / Q000635:transmission; D003141:Communicable Diseases / Q000635:transmission*; D004812:Epidemiologic Methods; D006801:Humans; D015233:Models, Statistical; D010322:Parvoviridae Infections / Q000635:transmission
Bayesian melding; Contact data; Italy; Parvovirus B19; Time use data; Varicella zoster virus