Journalist: Author, A Planet of Viruses; Science Ink: Tattoos of the Science Obsessed
When will disease be eradicated?

By the middle of the twentieth century, scientists and doctors were sure that it was just a matter of time, and not much time at that, before most diseases would be wiped from the face of the Earth. Antibiotics would get rid of bacterial infections; vaccines would get rid of viruses; DDT would get rid of malaria. Now one drug after the next are becoming useless against resistant parasites, and new plagues such as AIDS are sweeping through our species. Except for a handful of diseases like smallpox and Guinea worms, eradication now looks like a fantasy. There are three primary reasons that this question is no longer asked. First, parasites evolution is far faster and more sophisticated than anyone previously appreciated. Second, scientists don't understand the complexities of the immune system well enough to design effective vaccines for many diseases yet. For another, the cures that have been discovered are often useless because the global public health system is a mess. The arrogant dream of eradication has been replaced by much more modest goals of trying to keep diseases in check.

CARL ZIMMER is the author of Parasite Rex and writes a column about evolution for Natural History.