Dengue fever, African genetic admixture, and income in Brazil

People of African descent, and poorer people have a smaller risk of getting dengue hemorrhagic fever (DHF), according to previous studies. This study uses genetic admixture and measures of income to see how they co-vary with risk of DHF in Brazil. They find that ancestry and income are independently associated with DHF risk. They explain the income finding in two ways: 1) those with a higher income are more likely to be diagnosed, and 2) "exposure to dengue may also differ by socioeconomic level". One last thing. They state that "Income and percent African ancestry were only weakly correlated (r2=0.12) and not collinear." I'm not so sure they've completely established a genetic influence, but I guess now it's time for admixture mapping for genetic variants that contribute to DHF risk, all the while controlling for income.

Genetic ancestry and income are associated with dengue hemorrhagic fever in a highly admixed population
Ronald E Blanton, Luciano K Silva, Vanessa G Morato, Antonio R Parrado, Juarez P Dias, Paulo R S Melo, Eliana A G Reis, Katrina A B Goddard, Márcio R T Nunes, Sueli G Rodrigues, Pedro F C Vasconcelos, Jesuina M Castro, Mitermayer G Reis, Maurício L Barreto and M Glória Teixeira
European Journal of Human Genetics Published online 13 February 2008.

Abstract: To test whether African ancestry is protective for severe dengue, we genotyped 49 hospitalized cases of dengue hemorrhagic fever (DHF) as well as 293 neighborhood cases of dengue fever and 294 asymptomatic controls in Salvador, Bahia, Brazil. Ancestry-informative markers and 282 unlinked SNPs not associated with the clinical presentation of dengue were used to estimate ancestry. After controlling for income, both self-defined Afro-Brazilian ethnicity and African ancestry were protective for DHF (P=0.02, OR=0.28 and P=0.02, OR=0.13, respectively). Income or an index of income indicators, however, was also independently associated with the diagnosis of DHF.