Helminth infections and their effects on the immune system have been characterized to include a strong upregulation of Treg cells, increased production of IL-10 (Maizels and Yazdanbakhsh 2003; Wilson et al. 2005), and, in this study, an increased percentage IL-10 responders in children without ready access to a sewage system or tap water can be partially explained by this higher prevalence of helminth infections (data not shown; χ2p < 0.05). The gene discussed is IL10; the disease is helminthiasis.