Investigating disease clusters using point data
Does epilepsy occur in clusters? And if so, can we explain this clustering by exogenous or endogenous processes? In other words, what is responsible for this clustering: a) environmental factors and/or b) factors directly related to disease?
We recently have addressed this question analyzing the occurrence of epilepsy in a small village called Titule in The Democratic Republic of the Congo (DRC).
In 2014, an epilepsy prevalence study was conducted in Dingila and Titule, two localities within the onchocerciasis endemic Orientale Province of the DRC. Study investigators mapped the spatial distribution of epilepsy cases in the study area as well as clusters where there was a higher risk for epilepsy. Moran’s I statistic of spatial autocorrelation was calculated to test significant clustering of epilepsy prevalence, and to measure distance between clusters. The study found the prevalence of epilepsy to be 2.9% in Dingila, and 2.3% in Titule. Both rates are much higher than the epilepsy prevalence in non-onchocerciasis endemic regions in Africa. Epilepsy cases were clustered within and between adjacent households. Living close to a river infested with blackflies (the main vector of Onchocerca microfilariae) was found to be an individual risk factor for epilepsy.
Please download the full paper entitled Prevalence of River Epilepsy in the Orientale Province in the Democratic Republic of the Congo and read it carefully before answering the questions that will follow in the next step.
© KIT (Royal Tropical Institute), Amsterdam, the Netherlands