Dr. Paul Epstein is a physician in Boston, and the associate director of the Center for Health and the Global Environment at Harvard Medical School. He's created a niche as an eco-physician, exploring the link between increased illness and global warming. Illnesses such as heatstroke, asthma and allergies are the more obvious outcomes of a warmer and more polluted planet, but Epstein says an increase in infectious diseases such as malaria and West Nile virus may also be linked to the greenhouse effect.