Ross McKitrick has a new paper in the Journal of the Royal Statistical Society A, examining reasons for the eradication of malaria in some countries but not in others. You'll never guess what isn't a factor.
Malaria has disappeared in some countries but not others, and an explanation for the eradication pattern has been elusive. We show that the probability of malaria eradication jumps sharply when average household size in a country drops below four persons. Part of the effect commonly attributed to income growth is likely due to declining household size. The effect of DDT usage is difficult to isolate but we only identify a weak role for it. Warmer temperatures are not associated with increased malaria prevalence. We propose that household size matters because malaria is transmitted indoors at night, so the fewer people are sleeping in the same room, the lower the probability of transmission of the parasite to a new victim. We test this hypothesis by contrasting malaria incidence with dengue fever, another mosquito-borne illness spread mainly by daytime outdoor contact.
There's a discussion of the new paper here and the full paper can be seen here.