Individually, malaria and HIV/AIDS are two of the world's biggest killers, according to the World Health Organisation, so in regions where they are both endemic the interaction between them has serious implications for public health.

Pregnancy reduces the immune response, making women more susceptible to infection, so women with malaria are more likely to be infected with HIV as well.

"Malaria concentrates in pregnant women and their babies," says Dr Pedro Alonso, Director, Global Malaria Programme at WHO. "They need special attention to diagnose infection early and prevent vertical transmission of HIV."

Malaria and HIV overlap mainly in central Africa, in countries such as Mozambique, Zimbabwe, Angola and Zambia, where lack of funds hampers mosquito eradication programmes and poverty makes even simple individual protection such as insecticidal bednets and mosquito deterrents unaffordable for most.

"Malaria and HIV are poverty diseases, where poverty is both a cause and a consequence," says Dr Alonso. "Where HIV is the underlying condition it dramatically increases the risk of dying from malaria."

The core priority remains the eradication of malarial mosquitos, Dr Alonso points out, but better diagnostic tools for detecting malaria and HIV in pregnant women are also needed.

Dr Alonso says: "The core intervention is to prevent malaria by vector control, but individuals can be helped by providing bednets and simple diagnostic tests that can reduce infection."

Double infection with malaria and HIV is likely to increase as mosquitos become resistant to the current range of insecticides, he points out. "Resistance is spreading very quickly. It is a long term race and we need always to be one step ahead."

The pharmaceutical industry needs to devote research and development to the problem and donor countries should increase spending but combatting the double threat from malaria and HIV will also involve local governments.

"Money is always needed but it is not the only solution. We need countries to take ownership of the problems and the solutions," Dr Alonso concludes.