These climate change effects could cause illness in patients. Here’s how

Climate change—defined by the United Nations as “long-term shifts in temperatures and weather patterns”—may be impacting our health along with our planet.

Research indicates that climate conditions are becoming increasingly conducive to the transmission of multiple infectious diseases by promoting pathogens’ biological features and favoring vector transmission through modifying ecosystems and human behaviors.

Link between climate change and disease

In a study published in 2022 by Nature Climate Change, researchers reviewed the medical literature on established cases of illnesses affected by climatic hazards.^[] They found that 218 (58%) out of the 375 known human infectious diseases seemed to be made worse by one of 10 types of extreme weather connected to climate change.

Lead study author Camilo Mora, PhD, BSc, professor at the University of Hawaiʻi, Mānoa Department of Geography and Environment, recounted an example from his own life in an interview for PBS NewsHour.^[]

A flood in his house in rural Columbia in 2017 was the first time he had ever remembered having water in his living room. It created a breeding ground for mosquitoes, causing him to become infected with chikungunya, a dangerous and potentially lethal mosquito-borne virus. Years later, he still has joint pain.

Dr. Mora also told PBS NewsHour of a case from 2016 in Siberia in which an anthrax outbreak was purportedly linked to thawing of the permafrost. A heatwave in the region brought dead and long-frozen, anthrax-infected reindeer to the surface, which were fed upon by reindeer herds. Thousands died, and people were also reporinfected.

According to a 2021 article published by The Lancet Microbe, the increase in temperatures and precipitation has led to the rise in infectious diseases that include vector-borne diseases such as dengue, malaria, and leishmaniasis; enteric infections and diarrhea, including cholera, rotavirus infection, and vibriosis; and parasitic diseases, such as schistosomiasis.^[]

Mosquitos and tick-borne illnesses

Hotter summers, mild winters, and early springs have resulted in more time for mosquitos and ticks to reproduce, expand into different habitats, and spread more disease.

• Reported illnesses from tick, mosquito, and flea bites more than doubled between 2004 and 2018. During this time, more than 760,000 cases were reported, and nine new mosquito and tick-borne germs were discovered and spread in the US, according to the CDC.^[]

• The CDC report also recounted how warm weather conditions contributed to a 2012 US outbreak of West Nile virus that led to more than 5,600 illnesses and 286 deaths.

• According to the article in The Lancet Microbe, since 2012, Europe has seen a return of malaria, sustained transmission of Plasmodium vivax infections, increased Vibrio spp. infections, repeated summer outbreaks of West Nile virus, and local transmissions of chikungunya and Zika virus.

Animal-human contact

The CDC found that animals are fleeing to new locations after their natural habits are destroyed by climate change. This movement, especially to human-occupied regions, could potentially expand the spread of zoonotic disease due to increased contact between humans and animals.

Examples cited by the CDC include:

• Expansion of the rabies virus in new areas in the US

• An increase in Alaska’s population of voles, which can spread diseases like Alaskapox to humans

• Continued spreading of Ebola, Lassa, Rift Valley fever, and monkeypox in the US

Deadly algae blooms

Toxic algae blooms—rapid growths of cyanobacteria in rivers, lakes, and oceans that are precipitated by warmer temperature—are becoming a summer trend in US lakes, according to the CDC report.

These toxic algae blooms manifest as foam or scum on the water's surface and can have different colors. They can contaminate shellfish that, when consumed, can endanger our health.

Medical community position

The American Medical Association (AMA) backs the Intergovernmental Panel on Climate Change and “supports educating the medical community on the potential adverse public health effects of global climate change.”^[]

The AMA recommends the incorporation of climate change’s health implications into medical education, covering such topics as flooding, heat waves and resulting drought, infectious and vector-borne diseases, potable water supplies, and population displacement.

An increased awareness of climate change and its potential impact on public health could also have economic benefits. In the AMA article, Jonathan Patz, MD, MPH, cited research that found that a $30 investment in technology to reduce one ton of carbon dioxide emissions could result in a $200 savings in health costs.

Discussing the issue with patients

Physicians are speaking out about the need to address this growing public health threat with patients. In a 2021 opinion piece published in The BMJ, five clinicians urged their contemporaries to “learn how we can engage our patients in discussion about the climate and ecological emergencies.”^[]

The authors listed three conditions that are needed to facilitate productive discussions about the health ramifications of climate change with patients:

1. Talks on this topic must be viewed as a valid use of clinical time by administration and clinicians.

2. Clinicians should take into account where they are in their psychological “climate change journey,” as well as where the patient is on theirs.

3. In responding to patients, clinicians should validate their emotions of “eco-distress,” and they should provide information on community groups for patients who wish to take action on the issue.