Climate Change is Making Us Sick Climate change's contribution to the spread of infectious diseases

“Climate change” is a term becoming more well known today. Nonetheless, one very important aspect that most people do not know climate change has a large impact on is health. Pollution can cause respiratory and heart problems, increased temperature can cause heat stroke and worsen allergies, and the severe weather and natural disasters can lead to malnutrition, depression, injuries, and death. In fact, climate change has already and will continue to have a great influence on the spread of infectious diseases. The World Health Organization estimates "climate change will cause an additional 250,000 deaths per year between 2030 and 2050. Most will likely perish from malaria, diarrhea, heat exposure and under-nutrition.” We may be the ones who got us into this mess, but we can be the ones who get us out of it and lessen the horrible effects we could soon see.

HOw is climate change helping spread disease?

The answer: in many ways!

With increasing temperature and unpredictable swings of weather, agriculture is more difficult. Crop failure leads to malnutrition, population displacement, resource conflict, and more. Lack of available resources leads to worse hygiene habits. Harsh changes in temperature are a stress on the body. All of these things lead a person to be more susceptible to infectious diseases. Microorganisms are generally better at adapting to the changing environment and take advantage of the opportunity of a host with lowered immunity.

Additionally, the environment largely affects human behavior. People may seasonally migrate or have a different lifestyle during intense weather. During these times, humans often spend time indoors and close together if it is too hot, wet, or cold, and it gives pathogens a great opportunity to spread from one host to another. During droughts or times of flooding, water sources are scarce and thus is reduced hygiene during these times of tough survival.


Diseases can be transmitted in many different ways. Each pathogen is unique in its mode of getting from one place to the next. As seen in the diagram, most can be described in one of four ways: vector-borne, water-borne, food-borne, or air-borne - all of which climate change will greatly influence.

Many studies have been done exploring the connection between climate change, humans, and infectious diseases. For example, in a study done by researchers from all over the globe, it states "The health effects of climate change (including changes in climate variables and extreme weather events) on human infectious diseases are imposed through impacts on pathogens, hosts/vectors, and disease transmission."


A "host" is a living organism that a disease pathogen resides inside. A "vector" is an intermediate host that carries and transmits pathogens to other organisms which become hosts (like humans who will likely become infected and sick).


The swings in weather in consequence of climate change create an environment for mosquitoes to thrive and expand their range. Experts say that outbreaks are bound to become more common as the effects of climate change become more prevalent. Longer warm-weather seasons and changing rainfall patterns allow them to thrive for longer periods of the year and move into more areas.


Malaria claims more lives every year than any other disease, killing about 650,000 people a year. The mosquitoes that carry the virus and the parasites that cause the illness thrive where temperatures are warm. Scientists have already found evidence (for example, in Ethiopia, Peru, Bolivia, Ecuador, and Columbia) that malaria migrates to higher elevations during warmer years and during times of heavy rainfall or after natural disasters, which means that climate change will continue to expand malaria's geographical boundaries. The WHO explains, “Globally, temperature increases of 2-3ºC would increase the number of people who, in climatic terms, are at risk of malaria by around 3- 5%, i.e. several hundred million.”

Scientists explain the sudden outbreaks and expansion of chikungunya, yellow fever, and even the terrifying reemerging of zika virus with similar reasons. For example, chikungunya infection can be seen during periods of drought, as well as following heavy rains. Climate change is pushing weather patterns to these extremes. "As drought and heavy rainfall events increase with climate change and disease vectors spread, chikungunya prevalence is likely to increase, with the possibility of becoming endemic worldwide.”

the expansion of mosquitoes to non-tropical first world countries

Dengue Fever, which causes high fever, headaches, bone aches, rash, possible bleeding, seizures, or death, originated in Asia and Latin America. “In 2009, a case of dengue fever was reported in Florida for the first time in roughly 75 years; 27 more cases were reported in an outbreak that lasted for one year. Today, NRDC notes that mosquitoes capable of carrying and transmitting the disease have been found in 28 states, as well as Puerto Rico."

“The first cases of West Nile virus in the U.S. were reported in 1999; six years later, more than 16,000 patients had been diagnosed with the disease." It is now the most common mosquito-borne illness in the United States. It is spread when infected birds are bitten by bugs that then go on to bite humans. It can cause fevers accompanied by body aches, disorientation, diarrhea, neck stiffness, headache, joint pain, and tremors, and about 1 percent of people with West Nile go on to develop potentially fatal encephalitis or meningitis.

Ticks and Fleas

Lyme Disease is the most commonly diagnosed vector-borne disease in the U.S. There is usually 20,000 cases a year, but has increased to about 30,000 in recent years. If a deer tick bites a infected rodent, that tick can then bite a human and infect him with Lyme disease. Longer, hotter summers have expanded the geographical range of the deer tick, and Lyme disease has traveled to every state except Hawaii since it was first reported in 1975. It is also spreading to Canada, where thousands of people are becoming infected.

Some scientists fear that the increased temperatures from global warming will inevitably lead to an expansion of flea vectors into the northern hemispheres. Temperature and humidity are crucial for their development and survival. This, and our continued encroachment on natural areas, may provide new lines of transmission for a largely unknown pathogen population of wild fleas that we might not know much about. Fleas are hosts for many pathogens, and many of their diseases may re-emerge in epidemic form, like Rickettsia, murine typhus, and plague.

Rodents and other wildlife

There is evidence of diseases transmitted by rodents increasing with heavy rainfall or flooding. Mice and other rodents seek shelter from the storm, often with humans, and thus can more easily spread the infections they carry, like leptospirosis. They also join human dwellings during times of drought. Hantavirus pulmonary syndrome broke out in the U.S. in 1993 after a six-year drought and sudden heavy storms. Also, rodents and other animals are coming in more contact with humans because their forest homes are being destroyed. Forest fires force wildlife closer to human civilizations, and there is a direct link between the Ebola outbreak in Sierra Leone and their deforestation.


Water-borne diseases are any illness caused by drinking contaminated water, commonly with human or animal feces, which contain pathogenic microorganisms.

In developing countries, four-fifths of all illnesses are caused by water-borne diseases, with diarrhea being the leading cause of childhood death. Every day, an estimated 1,300 children die from diarrhea. History shows that floods favor cryptosporidium and gastroenteritis infections and cyclones increase cholera and leptospirosis. Natural disasters can contaminate freshwater supplies. Droughts may cause increased concentrations of pathogens in the available water. Diarrheal pathogens reproduce better in warmer conditions with prolonged sunshine. This has been seen all over the world, including Africa, South America, islands, India, and even around the Great Lakes and Colorado. Climate change will only increase these occurrences - and number of deaths.


An illness caused by eating food contaminated with bacteria, viruses, parasites, or toxins.

Diseases like botulism, hepatitis A, and more diarrheal illnesses can be transmitted through food. Epidemiologists have noted increases in salmonella and campylobacter infections after weeks of increased temperature. Salmonella occurrences in Australia specifically vary with elevated temperatures, and higher humidity has also correlated with decreased hospitalization rates for children diagnosed with food-borne rotavirus.

Ebola and more

Climate change worsens food security, forcing people to find alternative food sources during the shortages like eating infected wild animals to survive. Scientists traced the ebola outbreaks back to infected bat consumption. Many Africans ate bats because they were starving and contracted ebola. The bats were in closer proximity because of weather, another consequence of climate change .


Airborne diseases are spread when droplets of pathogens are expelled into the air due to coughing, sneezing or talking. One can then get the disease simply by breathing it in.

Wind assists the transport of air-borne diseases. Viruses and infections can be transported across entire oceans on dust particles. Wind has transported influenza all the way from Asia to the Americas over the Pacific. The desert dust during Asian dust storms increases the concentration of bacteria and fungi in the atmosphere. A study found influenza A virus was significantly higher during these dust storm days than on normal days. Wind can also change the spatial distribution of mosquitoes and help them fly farther.

As humans come in closer quarters to one another to avoid the effects of climate change, air-borne diseases can spread from one person to the next much quicker and easier.

So, what is being done about the spread of infectious diseases because of climate change? What can we do?

The spread of infectious diseases is an extremely complex process, and cannot be stopped with one solution.

Dr. Maria Neira, WHO Director, Department of Public Health says we should:

• Reduce carbon emissions to slow the rate of global warming while also saving nearly 2.5 million lives per year.

• Countries should make better use of early-warning information to predict the onset, intensity, and duration of epidemics. Then they could have medicines and vaccines ready.

• Health systems must become more resilient to climate change, particularly in developing countries. Hospitals should withstand powerful storms, heat waves, etc. Water and sanitation sources should stay clean during extreme weather events.

• Confront climate change and its health perspective with our political leaders. We must position health as a central pillar in the climate debate rather than an ancillary agenda.

There are many people, companies, and organizations that are making a difference.

The Enhancing National Climate Services (ENACTS), makes high-quality climate data available to decision makers in Africa, including those who are dealing with malaria. ENACTS monitors and reviews climate variability and gives decision makers a warning of when climate effects could trigger malaria outbreaks and when malaria interventions should be implemented.

Brilliant researchers are creating new vaccines to protect people from infectious disease, like this new, cheaper, heat-stable rotavirus vaccine talked about here -

Doctors Without Borders helps suffering people all over the world, whether they be flood victims, refugees fleeing from distress, or people stricken with malaria. They provide basic healthcare, vaccines, and more.

The United Nations Foundation works hand in hand with the World Health Organization, UNICEF and other UN agencies to develop and expand major initiatives to help families survive and thrive. Their global health priorities include: "preventing malaria deaths, eradicating polio, reducing measles mortality, mobile health for development, innovating health finance, improving health for every woman and every child."

And many, many more selfless and loving humanitarian efforts from people all over the world!

If we cannot help through the humanitarian efforts, there is plenty we can do from home to help with the growing problem of infectious diseases! We must reduce our carbon footprint to reduce our contribution to climate change.

According to NRDC, individuals can help improve the health of our Earth by:

• Driving more fuel-efficient cars or hybrid vehicles

• Using public transportation or cycling to work

• Using household appliances and devices that expend less energy

• Retrofitting their homes with ‘green’ technologies (like solar panels or compact fluorescent light bulbs)

• Researching alternative energies and getting involved in community-level projects that promote awareness of climate change causes and effects

Climate change is influencing almost every aspect of our lives, including our health and the spread of infectious diseases. Humans may be the ones who brought this problem upon ourselves, but we can also be the ones to alleviate the effects and get us out of it. Together, we can stop contributing to climate change and help every one of us who are affected by it.


Comics: Steve Sack -

Alex Hallat -



Created with images by NIAID - "E. coli Bacteria" • ArtsyBee - "mosquito malaria plaque" • mislav-m - "What makes you tick" • 422737 - "mammal rat eyes" • skeeze - "solar panel array power sun"

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