Although malaria was largely eradicated from North America half a century ago, it's still a major problem in many developing countries. When some 200 U.S. Marines were sent into Liberia recently, a third of them developed malaria. This happened despite medication that was supposed to confer immunity. The reason appears to be a combination of troops not taking their medication correctly, and the possibility that some of the marines came down with a strain of malaria that was resistant to the current drugs. Malaria has been around about as long as humans and comes in thousands of different strains. Some versions of malaria are more debilitating, and lethal, than others. This was discovered again during World War II, when some islands in the Pacific (like Ndene, in the Santa Cruz islands) were not used for American air bases because the local strain of malaria was so lethal. Even with the diligent application of insecticides and preventive measures (insect repellent and mosquito nets), a small percentage of troops still got malaria. And on the islands with the "killer strains" of malaria, the death toll of those with Malaria was too high. Other islands were used for the bases, even if it meant aircraft or ships had to travel another hundred miles or so. Even so, malaria was a major issue during World War II in the Pacific. During 1943 in Burma, for every soldier laid low by combat, 140 were put out of action by malaria (mostly) and other tropical diseases. This rate was got down to 60 in 1944 and 40 by 1945. The Japanese were not as successful in reducing the sickness rate, and it could be said that malaria was more helpful, than hurtful, to the allies. Even in places like Italy, where malaria was still present, as many troops were down with malaria as were out of action because of combat injuries. But during the Vietnam war, only 117 Americans died from malaria (about one in 480 deaths) . It was thought that medical science was on top of this ancient affliction. But as troops go to more different parts of the world, the chances of running into the nastier strains of malaria increase.