Malaria, the world's most widespread parasitic（寄生虫引起的） disease, kills as many as three million people every year—almost all of whom are under five, very poor, and African. In most years, more than five hundred million cases of illness result from the disease, although exact numbers are difficult to assess because many people don't （or can't） seek care. It is not unusual for a family earning less than two hundred dollars a year to spend a quarter of its income on malaria treatment, and what they often get no longer works. In countries like Tanzania, Mozambique, and the Gambia, no family, village, hospital, or workplace can remain unaffected for long.
Malaria starts suddenly, with violent chills, which are soon followed by an intense fever and, often, headaches. As the parasites multiply, they take over the entire body. Malaria parasites live by eating the red blood cells they infect （感染）. They can also attach themselves to blood vessels in the brain. If it doesn't kill you, malaria can happen again and again for years. The disease passed on to humans by female mosquitoes infected with one of four species of parasite. Together, the mosquito and the parasite are the most deadly couple in the history of the earth—and one of the most successful. Malaria has five thousand genes, and its ability to change rapidly to defend itself and resist new drugs has made it nearly impossible to control. Studies show that mosquitoes are passing on the virus more frequently, and there are more outbreaks in cities with large populations. Some of the disease's spread is due to global warming.
For decades, the first-choice treatment for malaria parasites in Africa has been chloroquine, a chemical which is very cheap and easy to make. Unfortunately, in most parts of the world, malaria parasites have become resistant to it. Successful alternatives that help prevent resistance are already available, but they have been in short supply and are very expensive. If these drugs should fail, nobody knows what would come next.

疟疾是由寄生虫引起的世界上传播最为广泛的疾病，每年死于疟疾的人多达300万---他们几乎都是年龄在5岁以下，家庭贫困的非洲儿童。多年来，尽管因很多人没有或无法寻求治疗而难于估计准确的数字，但是，也有5亿多人因疟疾而患病。一个年收入不到200美元的家庭将其收入的四分之一用于治疗疟疾是极其平常的，而且，他们所得到的常常是无法再工作。在坦桑尼亚，莫桑比克，冈比亚，长期以来，从家庭到村庄到医院到工厂，至今无不仍然受到影响。
疟疾发病突然，起初病人畏寒，接着高烧；常伴有头疼。由于寄生虫不断繁殖，它们遍布于病人的全身。疟疾寄生虫通过吞噬其感染的红血细胞而生存。疟疾寄生虫还能附着在病人大脑的血管内。如果疟疾没有使病人丧命，它会使其多年反复发病。疟疾是由感染了四种寄生虫中的一种寄生虫的雌蚊子传染给人类的。在地球上，蚊子和寄生虫是人类最致命的一对天敌---也是导致人类丧命的因素之一。疟疾有5，000个基因；其迅速变异的自身防护能力及其对新药的耐药性使人类几乎无法控制疟疾。研究表明，蚊子传播病毒越频繁，在人口众多的大城市爆发的疾病就越多。有些疾病的传播是由于全球气候变暖所导致的。
几十年来，在非洲，治疗疟疾的首选药物是氯喹。它是一种既便宜又容易制造的药物。不幸的是，在世界上大多数地区，疟疾寄生虫已经对它产生了耐药性。能够化解其耐药性的有效的可选药物已经制造出来了。但是，这些药物供应短缺，而且价格非常昂贵。如果这些药物也失去效力，谁也不知道以后会怎样。