The New York Times Magazine has a story by Tina Rosenberg about the resurgence of malaria in Africa. The best solution to the problem is, Rosenberg concludes, to use more DDT.
DDT use was banned in the early 1970s after it became apparent that widespread spraying causes serious environmental damage. By that time malaria was eradicated in Europe and America, and nearly eradicated elsewhere as well. But since then it has become apparent that complete eradication is in fact a "biological impossibility," and now efforts are focused on containing the disease and minimizing deaths. But the way DDT is used today in parts of central Africa (and indeed, in many other parts of the world, including Latin America) is what is called house-spraying. Walls and doors are sprayed, which kills and repels mosquitos for months following. The strategy may have some adverse health affects, but so far none are proven. On the other hand, its positive effects are proven -- dramatic reduction of malaria deaths. Other chemicals are available, but they are much more expensive, and anti-malaria funds are shockingly low (other diseases get most of the funding).
Because it is so cheap, it actually seems like it should be fairly simple to restore the use of DDT for house spraying (and continue the ban on its use as an agricultural insecticide). But there is now an unshakeable ethos amongst NGOs and UN aid organizations that DDT is bad, bad, bad. There is also a feeling of impropriety in prescribing a chemical for non-European countries that Europeans will never again have to use. As Rosenberg puts it: "Probably the worst thing that ever happened to malaria in poor nations was its eradication in rich ones."