A new study has found that droughts are reshaping how infectious diseases spread. Sustained dry spells are seeing rivers and reservoirs dwindle, fueling wildfires, and reshaping ecosystems across Europe and the United States. This, in turn, is changing the spread of infectious diseases, leading to surges in illnesses such as cholera and West Nile virus around the world.

Drought’s Impact on Disease Transmission

Researchers in the US have shown how drier conditions could make humans and wildlife more vulnerable to certain infectious diseases. Pieter Johnson, of the University of Colorado at Boulder, said that climate change is making droughts more variable and less predictable, which is becoming one of the defining challenges for understanding and managing disease in natural ecosystems.

Over the past few decades, more than 77% of Earth’s land experienced drier conditions, according to a United Nations report. The worst megadrought in 1,200 years in the western United States has drained crucial reservoirs such as Lake Mead to only a third of their capacity. Rising temperatures driven by climate change are making droughts more frequent, more intense, and more widespread.

Effects of Drought on Disease Patterns

While many infectious diseases are transmitted in water or through hosts such as mosquitoes that rely on water to reproduce, Johnson says drought doesn’t simply make those diseases disappear. For example, previous studies have found that periodic droughts in Florida increased the spread of St. Louis encephalitis virus, which is transmitted to people through infected mosquitoes.

Johnson and his study co-author Tara Stewart Merrill synthesized nearly 100 previous studies and identified the main mechanisms through which infectious diseases may respond to drought. They found that droughts can make certain parasites and disease carriers that are adapted to harsh conditions more successful. In North America, mosquito-borne diseases such as West Nile virus and St. Louis encephalitis virus have become more prevalent, in part because dwindling water levels have reduced the aquatic organisms like dragonfly larvae that prey on mosquito larvae.

Original reporting: KTBS 3 (Shreveport) — read the source article.