The Likoma Network Study: Context, data collection, and initial results

Abstract

The extent and structure of sexual networks have important consequences for the spread of sexually transmitted diseases such as HIV. However, very few datasets currently exist that allow a detailed investigation of sexual networks in sub-Saharan African settings where HIV epidemics have become generalized. In this paper, we describe the context and methods of the Likoma Network Study (LNS), one of the few studies that have collected extensive information on sexual networks in sub-Saharan Africa. We start by reviewing theoretical arguments and empirical studies emphasizing the importance of network structures in the epidemiology of HIV and other sexually transmitted infections (STI). The island setting of this study is described, and we argue that the choice of an island as a research site limited potential biases that may make the collection of sexual network data difficult. We then document our empirical strategy for the collection of sexual network data and the subsequent identification of sexual network partners. A description of the protocol for the collection of biomarker data (HIV infection) is provided. Finally, we present initial results relating to the socioeconomic context of the island, the size and composition of sexual networks, the quality of the sexual network data, the determinants of successful contact tracing during the LNS, and the prevalence of HIV in the study population.

Figure 1

Likoma Island on Lake Malawi

Figure 2. Geographic location of the sampled villages and village-specific participation rates

Each circle represents a dwelling unit. Dark circles represent housing units that were included in the sexual network survey. Empty circles represent housing units that were not included in this sampling frame. Denominators of the survey participation rates are the total number of eligible respondents (aged 18–35 and their spouses) in a given village, based on the initial household census. Denominators of the HIV testing participation rates are the total number of respondents who completed the sexual network survey in a given village. Island boundaries and location of dwelling units are approximate.

Figure 3

Age and sex distribution of all inhabitants residing on Likoma Island. De Jure population as of November 2005

Figure 4

Kaplan-Meier estimates of age at first marriage among inhabitants of Likoma Island

Figure 5

Outdegree distributions among survey respondents, by gender

Figure 5

Outdegree distributions among survey respondents, by gender

Figure 6

Flow chart of the linking process and terminology used

Figure 7

Indegree distributions among survey respondents, by gender

Figure 8

Indegree distribution among nonsurveyed network members, by gender

Figure 9

Total degree distributions among survey respondents, by gender

Figure 9

Total degree distributions among survey respondents, by gender

Figure 10

Characteristics of relationships reported during the sexual network survey at consecutive stages of the tracing and linking processes