Two aspects of the changing climate are expected to cause an uptick in communicable diseases: higher temperatures and increased rainfall.
The runoff from heavy rain is often contaminated with waste from agricultural fields, sewers, and other pollutants. During and after heavy rains, runoff can seep into homes, schools, and businesses.
Viruses, bacteria, and parasites in the floodwaters can make people and animals sick. In addition, they can cause dangerous fungal and mold infestations in buildings. After Hurricane Katrina, many homes were uninhabitable due to black mold contamination.
Fertilizer-rich runoff from fields causes outbreaks of blue-green algae in lakes and ponds—these outbreaks can make humans sick and can kill pets.
A warming climate has also caused an increase in diseases carried by insects like mosquitoes and ticks. The incidence of Lyme disease—which is spread by tiny deer ticks—has spiked in recent decades, as rising temperatures let ticks breed faster and spread north to regions that were previously too cold for them. Some experts predict that mosquito-borne viruses like West Nile and Dengue will also spread farther north as the climate warms.
The U.S. has successfully eradicated diseases—like malaria and yellow fever—in the past. With the impacts of climate change, we’ll have to set our sights on other diseases in the next century.