چکیده (انگلیسی):

Infectious disease spread depends on contact rates between infectious and susceptible individuals.
Transmission models are commonly informed using empirically collected contact data, but the
relevance of different contact types to transmission is still not well understood. Some studies select contacts
based on a single characteristic such as proximity (physical/non-physical), location, duration or
frequency. This study aimed to explore whether clusters of contacts similar to each other across multiple
characteristics could better explain disease transmission.
Methods: Individual contact data from the POLYMOD survey in Poland, Great Britain, Belgium, Finland and
Italy were grouped into clusters by the k medoids clustering algorithm with a Manhattan distance metric
to stratify contacts using all four characteristics. Contact clusters were then used to fit a transmission
model to sero-epidemiological data for varicella-zoster virus (VZV) in each country.
Results and discussion: Across the five countries, 9–15 clusters were found to optimise both quality of clustering
(measured using average silhouette width) and quality of fit (measured using several information
criteria). Of these, 2–3 clusters were most relevant to VZV transmission, characterised by (i) 1–2 clusters
of age-assortative contacts in schools, (ii) a cluster of less age-assortative contacts in non-school settings.
Quality of fit was similar to using contacts stratified by a single characteristic, providing validation that
single stratifications are appropriate. However, using clustering to stratify contacts using multiple characteristics
provided insight into the structures underlying infection transmission, particularly the role of
age-assortative contacts, involving school age children, for VZV transmission between households.
© 2016 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license
(http://creativecommons.org/licenses/by/4.0/).