A cohort study of risk factors for malaria among healthcare workers in equatorial guinea: Stay away from the ground floor

Background. Nonimmune long-term travelers to sub-Saharan Africa are at a high risk of contracting malaria. Most previous studies described risk factors and spatial distribution only in short-term travelers. This study describes the epidemiology and spatial distribution of malaria cases among expatriate healthcare workers in Equatorial Guinea. Methods. We conducted a cohort study evaluating the risk factors for malaria among healthcare personnel working in a hospital in Bata, Equatorial Guinea. Demographic data were recorded for all workers, and the spatial distribution of malaria cases within the hospital perimeters was determined. Results. During 2008 noncomplicated falciparum malaria was diagnosed in 13/102 workers (12.75%). On univariate analysis, the factors negatively associated with the risk of contracting malaria were living above the first floor and being older than 30 years. This association remained significant in multivariate analysis [hazard ratio (HR) = 0.24, 95% confidence interval [CI] = 0.06-0.91 for subjects living above the first floor and HR = 0.14, 95% CI = 0.04-0.52 for subjects above 30 years old]. Males and smokers had increased risk of contracting malaria on univariate analysis. However, this association was not significant in multivariate analysis (HR = 3.37, 95% CI = 0.87-13.1 and HR = 3.12, 95% CI = 0.83-11.75, for univariate and multivariate analysis, respectively). Low compliance with malaria prevention guidelines was observed in the study cohort. Conclusions. Living on the ground floor of apartment buildings in sub-Saharan Africa, as opposed to living on the top floors, confers an increased risk of acquiring malaria in long-term travelers with low compliance to prophylaxis. These findings should be discussed in advance with people intending to stay in sub-Saharan Africa for an extended period of time. The association between belonging to a younger age group and an increased risk of acquiring malaria, and the marginally significant increased risk of malaria in males and smokers, can probably be explained by increased exposure to malaria vectors. The compliance of healthcare workers with malaria prophylaxis is extremely low, as was previously described for other long-term residents.