In a cohort of HIV-infected persons living in endemic French Guiana, where the prevalence of positive skin tests is around 30%, we found that the incidence rate of disseminated histoplasmosis increased sharply as CD4 counts dropped below 100 per μL exceeding 10 per 100 person years, with a significant seasonal effect and a risk difference of 0.7 per 100 person years between dry and wet seasons [7,8]; the attributable risk percent in the overall HIV cohort (61%) implies that, overall, 61% of cases were attributable to the dry season and, arguably, to newly acquired infections. The gene discussed is CD4; the disease is infection.