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Feature photo by Photo above by seanmcgrath.

Global climate change is extending the reach of diseases once found only in tropical regions.

Do you think tropical diseases only occur in developing countries? Think again.

The World Health Organization (WHO) says diseases are spreading to temperate regions thanks to global warming.

Warmer temperatures and greater moisture extend the geographic range and season for disease-vector organisms such as insects and rodents. Below are diseases that could have you feeling the sting of global warming.


Malaria is spread by the Anopheles mosquito infected with the Plasmodium parasite. Warmer and wetter climates trigger increased mosquito abundance, biting rates, activity level, and accelerated incubation of their parasites. Winter temperatures must drop below 16ºC to prevent a malaria outbreak the following spring.

The U.N. Intergovernmental Panel on Climate Change (IPCC) projects that warmer temperatures will put 65% of the world’s population at risk of infection—an increase of 20%. This news is especially frightening in light of increased resistance to the chloroquine treatment drugs. Malaria has already hit Texas, New Jersey, Michigan, and New York.

Photo by otisarchives2.

Dengue Fever

Dengue fever is spread by the Aedes mosquito infected with the Flavivirus virus. The geographic range of the mosquito is limited by freezing temperatures that kill larvae and eggs, thus limiting transmission to tropical and subtropical regions.

With no vaccine, “breakbone” fever is considered the most serious mosquito-borne viral disease affecting humans.

But studies by the U.S. Environmental Protection Agency (EPA) and U.S. Department of Agriculture predict dengue’s encroachment upon temperate regions due to small increases in temperature.

The mosquito has spread as far north as Chicago and the Netherlands and to higher elevations of the Andes. With no vaccine, “breakbone” fever is considered the most serious mosquito-borne viral disease affecting humans.


Encephalitis is an arthropod-borne disease present in many forms, including St. Louis, equine, La Crosse, and West Nile. New York experienced outbreaks of both West Nile Virus (WNV) and St. Louis encephalitis in 1999 during its driest and hottest spring and summer in a century.

Those weather patterns favorable to outbreaks—heat and drought followed by heavy downpours—will likely occur more often with global warming. Small stagnant pools of water that accompany drought are big enough to support breeding mosquitoes but not populations of the frogs that prey on them.

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Bubonic Plague

Bubonic plague is spread by rodents and their fleas infected with the bacterium Yersinia pestis. A study in the Proceedings of the National Academy of Sciences reports that global warming promotes outbreaks of “black death.”

A 1ºC increase in springtime temperatures is predicted to lead to more than a 50% increase in the prevalence of the bacterium.

A study in the American Journal of Tropical Medicine and Hygiene reports a 60% rise in plague cases in New Mexico following wetter than average winters and springs. Wetter conditions enhance food resources for rodents and promote flea survival and reproduction.


Cholera is a waterborne disease present in drinking water and food contaminated with the bacterium, Vibrio cholerae. The WHO links the spread of cholera with increases in sea surface temperature, sea level rise, and El Niño-Southern Oscillation.

The U.S. EPA reports that algal blooms, which can be accompanied by cholera, become more frequent with warming temperatures. Cholera-harboring zooplankton also proliferates in warmer water temperatures.

Photo by otisarchives2.

What you can do

The IPCC warns that global warming will result in human mortality from infectious disease. Unlike the typical U.S. approach of emergency response to epidemics, a preventive approach would preclude unnecessary suffering, infection, and loss of life.

The Centers for Disease Control and Prevention (CDC) provides information on prevention, vaccines, and epidemics. Below are things you can do to reduce your chance of infection.

  • Get vaccinated for cholera and yellow fever when visiting areas with epidemics.
  • Prevent exposure to mosquitoes and ticks. You can do this by: wearing long sleeves and pants, and avoiding outdoor activity between dusk and dawn during mosquito season.
  • Eliminate sources of food and nesting places for rodents and treat your pets for fleas.
  • Tell your doctor if you work outdoors or have exposure to disease-vector organisms. The symptoms of many diseases are similar to the common flu and are therefore misdiagnosed, especially by doctors in temperate regions who are unfamiliar with the diseases.
  • Do your part to help stop global warming and support environmental legislation. Stopping global warming will slow the spread of diseases and obviate the need for widespread spraying of dangerous pesticides such as Malathion.
  • Often policymakers do not take action on environmental issues unless it affects human health so maybe this will be their wake-up call to do something about global warming.

    About The Author

    Mary Pfaffko

    Mary Pfaffko is a wildlife biologist from Washington, DC that goes around the world & back to look at birds, reefs, & stars.

    • James

      Malaria, Dengue Fever and Encephalitis have existed in cool climates (outside the tropics) for eons.

    • Bill the Cat

      true but they havent been very prevalent or widespread. with the small rise in temp the bacteria find it easier to multiply nd can also spread farther. atleast thats what i heard from my teacher please correct me if im wrong

    • Frank Rizzo

      Actually, there is maleria in siberia, ever go to alaska in the summer? You will get eatin alive! The earth has been cooling for the last 6 years, time to get your head our of your global anal warming buttocks. This is all about research money in the billions to everyone studying GW. You think they want the money train to go away?

    • Shark

      How about the ban on DDT killing more ppl than voodoo global warming? Please take your mindlessness to Aussieland ASAP.

    • In Search of the Tru

      I am afraid that many of the arguments that you make here cannot be supported by the facts. Diseases that are transmitted by mosquitoes have thrived over the last 40 years as a result of bans on DDT and other insecticides that were once used to control these pests. It was initially thought that high concentrations of DDT correlated to weakened eggshells in eagles and other large birds. This hypothesis was later proven false, but not until after a worldwide moratorium on DDT had been instituted. To make matters worse, there has been a push by many groups to "protect" the areas where mosquitoes breed such as swamps. In fact, many local building codes require runoff collection areas be constructed as an adjunct to new development. The greatest tragedy is that in tropical areas of the world, malaria and other such diseases were on the decline. DDT was an inexpensive way to reduce the mosquito population and therefore cut down on the incidence of such diseases. Without such controls, and with little access to adequate health care in the third world, many people die from these diseases today. Temperatures today are considerably cooler than they were in the 1930s and this year currently is tracking to be one of the 20 coldest of the last century. It is well documented that the temperature of the oceans has dropped considerably this year as well. This is completely inconsistent with the models that continue to predict a catastrophic increase in global temperatures. If there were indeed any warming, it would likely cause drying of areas where mosquitoes and bacteria breed reducing their population and hence the incidence of such diseases.

    • ianmack

      "It is well documented that the temperature of the oceans has dropped considerably this year as well." Well documented? Perhaps you could point out where you've heard ocean temperatures are dropping. Here's a study saying "The ocean warming and thermal expansion rates are 50 percent larger than previous estimates" ” target=”_blank”>…

    • Sara

      we're fucked

    • Bobbi

      Cooling by a predicted la nina 0.1 degrees after a 100 year rise in temperature…. Yeah.. that's statistically valid. The la nina effect actually predicts a greater than 0.1 C decrease as well as decreases in solar energy for the past little while. Everything except for human emissions are trying to make the earth cooler during the past couple years (as they always do in a scientifically predicted cycle) yet they have BARELY cooled. Nice global cooling proof.. and uh.. there is no malaria in alaska.. Ask anyone.. and there rate of malaria in Russia was 128 cases in a YEAR. Which has been increasing due to global warming. ” target=”_blank”>… You know how many cases are in africa? 500 MILLION. Yeah.. it's exactly the same… 5 million times more cases is nothing…

    • Makidian

      I agree with Sara, we are totally fucked.

    • ady

      there are a lot of other diseases that we should worry about besides the diseases 'spread' by global warming. Let's be serious.

    • In search of the Tru

      Look into the Argo project. Although it is sponsored by environmentalists who are eager to spin their data to support their climate change hypothesis, they have seen a stabilization in temperatures followed by a drop starting in or around 2004. This was widely reported in the NYT and on NPR earlier this year. Let me be clear– I believe that changes in temperature and local climates are inevitable. My disagreement is with those who are audacious enough to believe that these changes have been caused, or can be reversed by man. Geologically speaking man has existed for only a tiny epoch. Before this, the climate on this planet was prone to massive changes. In all likelihood this will continue with little regard to our hubris.

    • cortney

      they said THRIVING not that it doesnt exist anywhere else or never has.

    • Douglas Barnes

      The actual data (as opposed to angry internet posts) says otherwise. Furthermore,” target=”_blank”>…Furthermore, an even passing knowledge of statistics would make your post meaningless were it even true. Interesting hypothesis about the quest for grant money, though. It's right up there with "Nazca lines are proof of alien visitors."

    • Douglas Barnes

      Cooler now than in the 30s? that's simply not true. ” target=”_blank”>…

    • Adam

      Mmmm, I just love a good environmental discussion! What it comes down to is that we don't see things the way they are, we see things the way WE are. It seems to me that those people most adamant about Global Warming (either way) are those that have something to lose by their own argument not prevailing. Those who simply love the outdoors and want to see a healthy planet, normally take the side of Global Warming, as we've seen a change in the environment that is more than "cyclical."

    • putinroun

      Mobility of the human race at such a rapid method spreads more disease than anything . Historically speaking movements of people from one nation, country, or city group caused more widespread deaths than all the armament or global weather changes recorded in history. The black plague, native american indian populations, hawaiian populations, and Island populations eradicated from cultural exchanges. True insects and animals carry disease and spread them but not nearly as far and wide as the human virus carrier. Give it some serious thought people!!!! In other words( keep your ass at home) HAHAHA Fighting foreign wars spread more illness than any mosquito.

    • RyanColby

      I think its a absurd argument to say global warming is not happening. Let go of the silly pride that you have to fight against the bleeding liberals and ask yourself this; If this shit goes to hell, where will i be standing? Lets say the earth does cool down or warm up a bunch and we get fucked. Your malls, your cars, your silly politics wont matter, the only thing that will matter is survival. We should just be responsible and say hey this vividly strange but interesting world is for you, me and everyone to come. We all have a right to enjoy this land. Lets keep the future from coming to a halt.

    • Flea Treatment

      scary article… governments are not going to be focusing on the environment at the moment with the financial mess the world is in…

    • Tacnet

      + We should be more concerned about Global Warming and Climate Change because Typhoons are getting much stronger and there are greater incidence of Flooding. take for example the recent Typhoon Ketsana which devastated some countries in South East Asia.

    • David Becker

      Malaria is historically not a warm weather disease. It was endemic here in Michigan (which had lots of swamps) before air conditioning, screens on windows, insect repellant and urbanization. It is false to say that global warming has increased it; there is no reason it should. There has also been no observed increase in the intensity or number of violent typhoons, cyclones or hurricanes. Ditto flooding. These comments are simply talking points which violate the truth.

    • Beautiful Girls Gallery

      Global warming is becoming such an obvious problem that someone somewhere other than the US President needs to step up to help drive a massive campaign which aims to reduce Global Warming.

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