A team of infectious diseases experts has called for more awareness and preparedness in the medical field to deal with the impact of climate change on the spread of diseases.

Their article, published today in medical journal JAMA, raises the alarm about the emergence and spread of harmful pathogens. The authors also urge the medical community to update their education and training and take steps to combat global warming.

“Clinicians need to be ready to deal with the changes in the infectious disease landscape,” said lead author George R. Thompson, a professor at the UC Davis School of Medicine in the Department of Internal Medicine, Division of Infectious Diseases, and the Department of Medical Microbiology and Immunology.

“Learning about the connection between climate change and disease behavior can help guide diagnoses, treatment and prevention of infectious diseases.”

Changing infectious diseases landscape

One type of infectious disease is vector-borne disease, caused by pathogens carried by vectors like mosquitoes, fleas and ticks. Some diseases caused by vectors are dengue, malaria and Zika.

Changing rain patterns are expanding vectors’ range and their active periods. Shorter, warmer winters and longer summers are also linked to more vector-borne diseases. For example, diseases caused by ticks (like babesiosis and Lyme disease) are now occurring in the winter too. They’re also being found in regions farther west and north than in the past.

“We’re seeing cases of tick-borne diseases in January and February,” said first author of the study Matthew Phillips, an infectious diseases fellow at Massachusetts General Hospital and Harvard Medical School. “The tick season is starting earlier and with more active ticks in a wider range. This means that the number of tick bites is going up and with it, the tick-borne diseases.”

Another concern is malaria. The mosquitos that transmit the disease are expanding northward, a climate-induced change. Changing rain patterns have led to more mosquitos and a higher disease transmission rate.

Zoonotic diseases, such as plague and hantavirus (carried by rodents), are also showing changes in incidence  and location. The experts noted changes in animal migration patterns and natural ranges. Due to their habitat loss, wild animals are coming closer to humans. With that comes a higher risk of animal diseases spilling over to humans and for new pathogens to develop.

Fungal infections, storm surges

The study also pointed to the emergence of new fungal infections, such as Candida auris (C. auris), and changes in the location of some fungal pathogens. For example, the fungal infection Coccidioides (also known as Valley fever) was endemic to hot, dry areas in California and Arizona. But Valley fever was recently diagnosed as far north as Washington State.

Changes in rain patterns and coastal water temperature can also affect the spread of waterborne diseases, such as E. coli and Vibrio. According to the team, the sea level is rising, and storm surges and coastal flooding that used to be rare or extreme events are happening more frequently.

Call for medical community to take steps

The team called for stronger measures for infectious disease surveillance and urged medical clinicians to anticipate the changes in infectious disease patterns.

“Clinicians need to be ready to deal with the changes in the infectious disease landscape,” said Thompson. “Learning about the connection between climate change and disease behavior can help guide diagnoses, treatment and prevention of infectious diseases.”

Another concern is malaria. The mosquitos that transmit the disease are expanding northward, a climate-induced change. Changing rain patterns have led to more mosquitos and a higher disease transmission rate.

Zoonotic diseases, such as plague and hantavirus (carried by rodents), are also showing changes in incidence  and location. The experts noted changes in animal migration patterns and natural ranges. Due to their habitat loss, wild animals are coming closer to humans. With that comes a higher risk of animal diseases spilling over to humans and for new pathogens to develop.

The study also pointed to the emergence of new fungal infections, such as Candida auris (C. auris), and changes in the location of some fungal pathogens. For example, the fungal infection Coccidioides (also known as Valley fever) was endemic to hot, dry areas in California and Arizona. But Valley fever was recently diagnosed as far north as Washington State.

Changes in rain patterns and coastal water temperature can also affect the spread of waterborne diseases, such as E. coli and Vibrio. According to the team, the sea level is rising, and storm surges and coastal flooding that used to be rare or extreme events are happening more frequently.

The team called for stronger measures for infectious disease surveillance and urged medical educators to train clinicians to anticipate the changes in infectious disease patterns.

This study was partially supported by National Institutes of Health grants T32AI007061 and 5U19AI166798.

Citation: Matthew C. Phillips, MD, PhD^1,2; Regina C. LaRocque, MD, MPH^1,2; George R. Thompson III, MD^3,4. JAMA. Published online March 20, 2024. Infectious Diseases in a Changing Climate10.1001/jama.2023.27724

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