Spatial patterns of incident XXXX cases and their household contacts in a single clinic catchment area of Chongwe District, Zambia.

@entity311 @entity2166 @entity281 @entity138
BACKGROUND: @entity2166 ( @entity2166 ) for @entity311 is a strategy that may be used to complement passive surveillance, as passive surveillance fails to identify @entity281 that are asymptomatic or do not seek care. The spatial and seasonal patterns of incident (index) cases reported at a single clinic in Chongwe District were explored. METHODS: A @entity2166 strategy was implemented from June 2012 to June 2013 in a single catchment area in Chongwe District. Incident (index) cases recorded at the clinic were followed up at their household, and all household contacts were tested for @entity311 using rapid diagnostic tests (RDTs). GPS coordinates were taken at each index household. Spatial analyses were conducted to assess characteristics related to clustering, cluster detection and spatial variation in risk of index houses. Effects of season (rainy versus dry), distance to the clinic and distance to the main road were considered as modifying factors. Lastly, logistic regression was used to identify factors associated with the proportion of household contacts testing @entity138 positive. RESULTS: A total of 426 index households were enrolled, with 1,621 household contacts (45% @entity138 positive). Two space-time clusters were identified in the rainy season, with ten times and six times higher risk than expected. Significantly increased spatial clustering of index households was found in the rainy season as compared to the dry season (based on K-function methodology). However, no seasonal difference in mapped spatial intensity of index households was identified. Logistic regression analysis identified two main factors associated with a higher proportion of @entity138 positive household contacts. There was a 41% increased odds of @entity138 positive household contacts in households where the index case was under 5 years of age [OR = 1.41, 95% confidence intervals (1.15, 1.73)]. For every 500-m increase in distance from the road, there was a 5% increased odds of @entity138 positive household contacts [OR = 1.05 (1.02, 1.07)], controlling for season. DISCUSSION: Areas of increased report of @entity311 persist after controlling for distance to the clinic and main road. Clinic-based interventions will miss asymptomatic, non-care seeking @entity281 located farther from the road. @entity2166 may identify additional @entity281 missed at the clinic.
