El Nino Could Boost Lyme Disease in Western U.S.

By Randy Dotinga

HealthDay Reporter

MONDAY, Oct. 24, 2016 (HealthDay News) -- The big shifts in rain and warmth caused by El Nino and La Nina conditions may boost Lyme disease and intestinal infections in parts of the United States, a new study suggests.

Over four decades, more tick-borne disease in the West and more gastrointestinal disease in the Northeast were tied to the periodic swings in weather conditions, researchers said.

They believe the findings provide insight into potential effects of climate change.

"There are important links between the environment and infectious disease risk, not only in low-income countries, like places with a lot of malaria, but in high-income countries like the U.S. and Canada, too," said study lead author Dr. David Fisman. He's a professor of epidemiology at the University of Toronto's Dalla Lana School of Public Health.

"Hopefully, people will understand that environmental change can impact their health, not only directly -- via extreme heat or cold -- but also indirectly via impacts on infectious disease."

El Nino and La Nina are bands of warm water and cold water, respectively, which occur periodically in the tropical Pacific Ocean. They can affect weather in other parts of the world.

In the United States, El Nino is generally tied to wetter weather in the South and drier conditions in the Pacific Northwest.

For the new study, the researchers examined U.S. hospitalization data for various kinds of diseases from 1970 to 2010 and looked for possible links to El Nino-type events.

"We discovered that the risk of some diseases, especially diarrhea diseases and tick-borne disease, does seem to be affected, but the direction of effect is different in different parts of the U.S.," Fisman said.

The researchers aren't certain that weather shifts directly caused the varying patterns in illness they've detected.

Still, they saw a surge of diseases spread by ticks, mainly Lyme disease, in Western states about a year after an El Nino.

Diseases that cause diarrhea seemed to decrease in the West but increase in other areas, especially the Northeast, in relation to the weather conditions, Fisman said.