AIDS prevention has seen two breakthroughs this month. The big news is the protective value of circumcision. But there is another important finding: AIDS and malaria mix with disastrous effects.

In a paper published in Science, researchers calculated that the interaction of the diseases increased AIDS cases by 8 per cent and malaria by 13 per cent. Over 25 years, that meant a million extra cases of malaria. The researchers drew on earlier findings that HIV-positive people who get malaria experience a spike in the level of the AIDS virus in their blood. During that spike, they are supercontagious, with double the chance of infecting a sexual partner.

One important lesson of the study is that protecting HIV-positive people from malaria would also limit the spread of AIDS. They need insecticide-treated bed nets to sleep under, and should take a daily dose of the antibiotic cotrimoxazole. Combining bed nets and cotrimoxazole with antiretroviral therapy reduced malaria cases in HIV-positive people by 95 per cent in one study.

Cotrimoxazole is cheap, but not widely used in poor countries. Donors eager to fight AIDS have shown less interest in improving Africa’s health systems, training health workers and equipping clinics. The new study hints that that it is all one fight.