This is a randomized placebo controlled trial. Malaria chemoprophylaxis with mefloquine in asymptomatic HIV-infected adults living in a malaria endemic region of Luanshya, Zambia will be compared to a placebo control group and followed up for 18 months. In Zambia prompt treatment of malaria cases is the mainstay of malaria control; antimalarial chemoprophylaxis is not currently recommended for general use so that the use of placebo as a comparator in this study is justified. We will analyse safety and efficacy of mefloquine, malaria and AIDS related parameters at predefined time points, and verify if this intervention could produce a slower decrease in CD4 counts compared to passive case management of malaria. Specific designed studies taking into account possible confounding parameters (and interactions) are needed to measure the impact of malaria control in an HIV endemic environment. In particular, the question should be answered if malaria control has an impact on the disease progression of HIV. The possible impact of these interventions on morbidity and mortality taking into account these parameters might have a major public health impact. This might be on the use of antiretroviral drugs, the incidence of clinical (eventually severe) malaria and spread of antimalarial resistance through immune compromised HIV patients (with and without antimalarial treatment). Studies of alternative strategies that contribute (next to antiretrovirals) to the control and prevention of HIV pandemic are equally important and urgently needed. The need to design these strategies is critical given the high incidence of malaria and HIV in countries in Sub Saharan Africa such as Zambia and its serious impact on survival and the socio-economic situation. Moreover, a cost-benefit analysis might show that some alternative strategies have a major impact on the field with less technical, financial and social constraints than the strategies recommended so far.

All HIVP patients will be treated for opportunistic infections (OI) and receive antiretroviral drugs following the National guidelines on Management and Care of Patients with HIV/AIDS (also if this occurs after the study period). At the time they need cotrimoxazole prevention or/and receive antiretrovirals they would have reached a study endpoint and will be excluded from the trial though the follow up will continue.