Dengue is not well documented in Africa. In Cameroon, data are scarce, but dengue infection has been confirmed in humans. We conducted a study to document risk factors associated with anti-dengue virus Immunoglobulin G seropositivity in humans in three major towns in Cameroon.
A cross sectional survey was conducted in Douala, Garoua and Yaounde, using a random cluster sampling design. Participants underwent a standardized interview and were blood sampled. Environmental and housing characteristics were recorded. Randomized houses were prospected to record all water containers, and immature stages of Aedes mosquitoes were collected. Sera were screened for anti-dengue virus IgG and IgM antibodies. Risk factors of seropositivity were tested using logistic regression methods with random effects.
Anti-dengue IgG were found from 61.4% of sera in Douala (n = 699), 24.2% in Garoua (n = 728) and 9.8% in Yaounde (n = 603). IgM were found from 0.3% of Douala samples, 0.1% of Garoua samples and 0.0% of Yaounde samples. Seroneutralization on randomly selected IgG positive sera showed that 72% (n = 100) in Douala, 80% (n = 94) in Garoua and 77% (n = 66) in Yaounde had antibodies specific for dengue virus serotype 2 (DENV-2).
Age, temporary house walls materials, having water-storage containers, old tires or toilets in the yard, having no TV, having no air conditioning and having travelled at least once outside the city were independently associated with anti-dengue IgG positivity in Douala. Age, having uncovered water containers, having no TV, not being born in Garoua and not breeding pigs were significant risk factors in Garoua. Recent history of malaria, having banana trees and stagnant water in the yard were independent risk factors in Yaounde.
In this survey, most identified risk factors of dengue were related to housing conditions. Poverty and underdevelopment are central to the dengue epidemiology in Cameroon.
General awareness of dengue fever in Africa, and particularly in Cameroon, is weak. Many acute febrile illnesses are considered as malaria, although not laboratory confirmed, and the diagnosis of dengue fever is seldom evoked while its laboratory confirmation is even more seldom obtained. On the basis of anti-dengue virus IgG seropositivity in humans, our survey demonstrated that dengue virus transmission occurred in the three main towns of the country. Although the findings varied according to the location, identified risk factors of anti-dengue virus seropositivity were commonly related to housing conditions. Taking into account the risk factors identified in Douala, practical ways to lower the risk of dengue virus transmission are long term development and improvement of sanitation and education. We concluded that poverty and underdevelopment are central to the problem of dengue virus transmission in urban areas in Cameroon.