"Ever since we became a species, some 200,000 years ago, s have been responsible for untold amounts of human suffering and countless deaths. For instance, some experts believe that Homo sapi­ens almost became extinct as the result of epidemics caused by malaria that coincided with a time when our numbers were perhaps as low as 400,000 individuals. The worst part is that this killer is still with us. In just over the past one hundred years, as many people have died from worldwide as now live in the United States. While the number of people dying from this one parasite is high, consider the fact that ma­laria in all its forms (there are four) infects some two billion individuals each year. This reduces the mortality rate to around 1 percent, making this group of infectious agents some of the most successful parasites on the planet."