Public health experts warn that as climate change becomes more serious, humans are likely to be hit by an increasing number of health problems, ranging from heat strokes to infectious diseases. Milder winters and increased flooding could help insects breed and extend their ranges, perhaps leading to more tick-borne infections like Lyme disease. Mosquitoes in particular are expected to thrive under climate change, and Physicians for Social Responsibility warns that malaria, encephalitis, yellow fever, and other infectious diseases may extend out of tropical regions to countries in the North, including the U.S. Rodents carrying diseases like hantavirus may also grow more numerous, according to a report released last week by the Ecological Society of America and the Union of Concerned Scientists.