Sexual network analysis of a gonorrhoea outbreak.
OBJECTIVE
Sexual partnerships can be viewed as networks in order to study disease transmission. We examined the transmission of Neisseria gonorrhoeae in a localised outbreak in Alberta, Canada, using measures of network centrality to determine the association between risk of infection of network members and their position within the sexual network. We also compared risk in smaller disconnected components with a large network centred on a social venue.


METHODS
During the investigation of the outbreak, epidemiological data were collected on gonorrhoea cases and their sexual contacts from STI surveillance records. In addition to traditional contact tracing information, subjects were interviewed about social venues they attended in the past year where casual sexual partnering may have occurred. Sexual networks were constructed by linking together named partners. Univariate comparisons of individual network member characteristics and algebraic measures of network centrality were completed.


RESULTS
The sexual networks consisted of 182 individuals, of whom 107 were index cases with laboratory confirmed gonorrhoea and 75 partners of index cases. People who had significantly higher information centrality within each of their local networks were found to have patronised a popular motel bar in the main town in the region (p = 0.05). When the social interaction through the bar was considered, a large network of 89 individuals was constructed that joined all eight of the largest local networks. Moreover, several networks from different communities were linked by individuals who served as bridge populations as a result of their sexual partnering.


CONCLUSIONS
Asking clients about particular social venues emphasised the importance of location in disease transmission. Network measures of centrality, particularly information centrality, allowed the identification of key individuals through whom infection could be channelled into local networks. Such individuals would be ideal targets for increased interventions.
Department of Epidemiology and Biostatistics, McGill University, 1020 Pine Avenue West, Montreal, Quebec, Canada H3A 1A2. prithwish.de@mail.mcgill.ca
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Singh
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Yacoub
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Jolly
D000293:Adolescent; D000328:Adult; D016358:Contact Tracing / Q000379:methods*; D004196:Disease Outbreaks; D005260:Female; D006069:Gonorrhea / Q000453:epidemiology* / Q000635:transmission; D006801:Humans; D008297:Male; D008875:Middle Aged; D011792:Quebec / Q000453:epidemiology; D012111:Residence Characteristics; D012307:Risk Factors; D012747:Sexual Partners