Infectious Diseases and Climate Change

Climate change is expected to impact the spread of infectious diseases in Washington state. Shifts in weather patterns like warmer summers, milder winters, and changes in rainfall, for example, might change the distribution of infectious diseases.

One Health Approach

One Health is a collaborative effort of multiple disciplines working locally, nationally, and globally to improve the health of our ecosystem, including humans, animals, plants, and our environment. One Health promotes multi-sectoral and cross-disciplinary collaboration to solve health challenges, like climate change. Read more about our One Health work.

Foodborne and Waterborne Enteric Diseases

Enteric diseases are a group of illnesses primarily affecting the gastrointestinal tract. These diseases are typically caused by various pathogens such as bacteria, viruses, and parasites, and they are often transmitted through contaminated food or water, or via direct person-to-person contact, and are highly sensitive to changes in climate. Enteric diseases monitored in Washington include:

Rising temperatures, altered precipitation patterns and extreme weather events can influence the incidence and distribution of these diseases.

Rising Temperatures

Warmer temperatures can enhance the survival and proliferation of foodborne and waterborne pathogens, leading to an increased risk of contamination. Heatwaves may affect the storage and transportation of perishable foods, potentially accelerating the growth of bacteria and compromising food safety.

Altered Precipitation Patterns

Changes in precipitation patterns, including more intense rainfall and flooding, can contribute to the spread of foodborne and waterborne diseases by disrupting sanitation systems, contaminating food and water supplies, and affecting produce growing areas. Excessive rainfall and flooding can contaminate crops with harmful microorganisms. Drought, exacerbated by climate change, can have significant implications for foodborne illnesses including water scarcity and contamination, and reduced produce yields potentially leading to changes in agricultural practices including using irrigation from unconventional sources. Some foodborne illnesses, such as those caused by E. coli or Salmonella, can have animal origins, and drought-related stress on livestock may contribute to the transmission of these pathogens. These alterations in environmental conditions can challenge existing food safety measures, increasing the risk of foodborne outbreaks.

Extreme Weather Events

Extreme weather events, such as hurricanes, floods, heatwaves, and storms, can have profound effects on food safety and contribute to an increased risk of foodborne illnesses. The impacts are diverse and can occur at various stages of the food supply chain, from production and processing to distribution and consumption. For example, storms and floods can contaminate water sources used in agriculture and food processing.  Contaminated water can introduce pathogens to crops, seafood, and other food products, increasing the risk of foodborne illnesses when consumed.

Changes to Coastal Waters

Climate change can influence temperature, salinity, and nutrient availability in coastal waters, contributing to increased growth and distribution of marine bacteria, including Vibrio, the pathogen that causes vibriosis. Rising water temperatures can create more favorable conditions for Vibrio to grow and proliferate. Changes in ocean salinity and nutrient availability can also influence Vibrio habitats, leading to variations in the geographic distribution and abundance of the bacteria among coastal waters. These factors can contribute to an increased risk of shellfish becoming contaminated with Vibrio bacteria, which may result in more illnesses of vibriosis among people. 

Addressing the intersection of climate change and foodborne illnesses requires a comprehensive approach. This includes implementing robust food safety regulations, enhancing surveillance and monitoring systems, and promoting sustainable agricultural practices resilient to climate variability. Collaboration at the global level is essential to mitigate the impacts of climate change on food safety and ensure the well-being of populations worldwide.

Zoonotic and Vector-borne Diseases

Zoonotic and vector-borne diseases are caused by infectious agents that spread from animals and arthropods (such as mosquitos and ticks) to people. The environmental and ecosystem health impacts of climate change influence the behavior, geographic range, and health of animals and vectors, which can change the distribution and human health risk of these diseases. Extreme weather events, such as flooding or wildfires, can bring animals into closer contact with people or their environments as they seek shelter. Increased interactions between animals and people change the way diseases are spread between them. In Washington state, several zoonotic and vector-borne diseases are anticipated to pose an increased risk to people as our climate changes:

Mosquito-borne Diseases

Warmer average temperatures throughout the state could result in expanded mosquito distribution. Warmer temperatures also speed up the life-cycle of mosquitoes, allowing adult mosquitoes to mature faster, increasing people’s risk of exposure to West Nile virus (WNV).

The relationship between drought and the spread of WNV is complex. Climate experts anticipate increased frequency of drought due to climate change. Drought can reduce mosquito habitat. However, scarce water sources can also bring bird host reservoirs and vector mosquitoes closer together, thereby helping amplify the virus. Mosquito habitat created by irrigation systems can likewise offset the impact of drought conditions.

Tick-borne Diseases

Factors that may impact the distribution of ticks and the infectious agents they carry include climate, presence of animal species, and interactions between humans and the environments where they live, work, and play.
Changes in temperature and precipitation will impact the distribution and seasonality of ticks. These changes will also expand the geographic range of disease-carrying ticks, leading to increased risk of tick-borne diseases.

Environmental Fungal Diseases

Environmental pathogens grow in soil, water, or other environments. Environmental diseases that may increase in Washington state due to climate change include Valley Fever and Cryptococcus gattii infection.

The Coccidioides fungus that causes Valley Fever is present in areas of low rainfall and high temperatures. Coccidioides fungi have been detected in south-central Washington State. As an environmental fungus living and growing in soil, its ability to survive and thrive in different areas will change with changing environments. Factors that affect the ability of Coccidioides to live and grow include climate, soil conditions, and the presence of other species in the soil and environment. Due to these complex factors, it is not simple to predict where and how Coccidioides growth areas will change. As higher temperatures and lower rainfall occurs, habitat areas for Coccidioides may increase.

Cryptococcus gattii lives in the environment on trees and in the soil; it has been found in northwestern Washington state. Similar to Coccidioides, the ability for Cryptoccocus gattii to survive in different areas will change with changing environments. 

Addressing the Climate Impact on Zoonotic and Vector-borne Disease

Addressing the intersection of climate change and zoonotic or vector-borne diseases requires a comprehensive and multisectoral approach. This includes enhancing surveillance and monitoring systems across human, animal, and environmental health and improving communication to populations at risk.


Zoonotic Climate Impacts Flyer (PDF)
Zoonotic Climate Impacts Flyer, Spanish (PDF)
CDC Climate and Vector-borne Disease
CDC Climate and Vector-borne Disease Flyer (PDF)
CDC Climate, Food and Waterborne Disease
CDC Climate and Fungal Disease
CDC Climate and Infectious Disease
CDC Climate and Infectious Disease Flyer (PDF)