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International Biometric Society INVESTIGATING SOCIAL CONTACT STRUCTURES AND THEIR INTERACTIONS WITH DIFFERENT TYPES OF TIME USE IN SUB-SAHARAN AFRICA Alessia Melegaro1, Emanuele Del Fava1, Piero Poletti1,2, Constance Nyamukapa3, and Simon Gregson3 1 Bocconi University, Milan, Italy Fondazione Bruno Kessler, Trento, Italy 3 Imperial College London, UK 2 In the field of modelling infectious diseases, epidemiological literature has shown the importance of considering social contact structures when investigating the routes of transmission of airborne infections diseases and the subsequent effect of control measures put in act in order to stop transmission. Traditional transmission models assume that people mix with each other in a homogenous way. However, this assumption is far from being realistic. In the past, research has tried to solve this problem by hypothesizing theoretical social structures, most of which assumed high assortativeness between people belonging to the same age group and more or less homogeneity for contacts between people belonging to different age groups (Anderson and May, 1991). However, in recent years research has moved forward from this approach by directly collecting field data on social contacts among people, including both physical and conversational contacts. Seminal studies in Europe showed that, along with a strong assortativeness in contacts between people of the same age group, to a greater extent among school-aged children, a great number of contacts is registered between adults and children. Stratifying contacts per location (household, school, workplace, and general community), it has been seen that those high-frequency contacts occurred mostly in household, usually between parents and their children. The school is another location characterized by a high frequency of contacts. In order to validate these contact data, their inclusion in models for transmission of childhood infections has lead to a far better explanation of the available infection data (seroprevalence and incidence data). However, many questions still remain open. One of these regards the investigation of the impact of social contact structures in contexts characterised by an ongoing demographic transition, as it is the case of Sub-Saharan Africa and other middle/low income countries. In countries that show at the same time large households, composed of people belonging to different generations, mostly in rural areas, and smaller households in the fast-growing urban areas, can we expect a different stratification of social contact structures between different age groups and locations? Moreover, how do social contact structures differ among people with very different use of their time during the day? We expect indeed different patterns between someone who spends most of his/her day at home and someone who spends his/her day either at school or on the workplace. We try to answer all these questions by collecting, for the first time to our knowledge, field data on social contacts and on time use from Zimbabwe, a Sub-Saharan African country still prevalently rural, where HIV has reached an endemic state. Our sample consists of around 1200 subjects mainly living in two different areas, one mostly rural and one mostly urban. People included in the study were asked to keep a diary for two continuous days, randomly allocated, in order to collect information on their social contacts and on their time use. As regards contacts, they were asked to give information on age, gender, relationship, type (physical/non-physical), and location for each of their contacts; as regards time use, they were asked to record their location (household, school, workplace, general community) in different time slots during the day and also to give a rough estimate of the number of people around them. The combination of these two sources of data will allow us to better characterise the shape of social contact patterns for different types of time use and to subsequently inform a mathematical model designed to assess the impact of different policy measures on the control of the transmission of infectious diseases of high concern in the country. International Biometric Conference, Florence, ITALY, 6 – 11 July 2014