Climate change helps spread dengue fever in 28 states

Just in time for the summer mosquito season, the Natural Resources Defense Council (NRDC) released a report last week detailing the latest climate-based threat to human health.

The two mosquito species capable of carrying dengue fever are rapidly spreading across the southern United States, increasing the incidence of the disease. We already knew that “Climate change is the biggest global health threat of the 21st century” – now, it seems, we’re reaching the point where “threat” turns into “harsh reality.”

The report tells it straight:

Global warming threatens to further exacerbate the spread of many infectious diseases because increases in heat, precipitation, and humidity can foster better conditions for tropical and subtropical insects to survive and thrive in places previously inhospitable to those diseases.

And, as the NRDC discusses in its report, dengue fever is top among those diseases. Also known as “breakbone,” dengue causes “fever, severe headache, backache, joint pains, nausea and vomiting, eye pain, and rash.” The Center for Disease Control (CDC) warns that, “if unrecognized and not properly treated,” dengue can develop into dengue hemorrhagic fever (DHF) and possibly kill its host. Unpleasant, right?

Once considered exclusive to the tropics, dengue has experienced a 30-fold increase in incidence rates during the last 50 years and has since spread to more temperate climates, now including huge swaths of the United States.

While previously limited to the United States-Mexico border, the Aedes aegypti and Aedes albopictus mosquitoes have now spread to 28 American states (check out the map), threatening an estimated 173.5 million Americans, particularly in the southern and mid-Atlantic regions. The report describes how climate change exacerbates the situation:

Warmer temperatures boost the speed of development of adult mosquitoes, increasing their numbers. Female mosquitoes bite more frequently in hotter temperatures, and warmer winters enable mosquitoes to survive in areas that were formerly too cold. Higher temperatures also shorten the time it takes for the virus inside the mosquito to develop and become infective.

Worldwide, about 2.5 billion people live in areas threatened by the mosquito species that can carry dengue. NRDC projects this number to increase to 5.2 billion people by 2085, and as America’s climate becomes more tropical (see: “Our hellish future: Definitive NOAA-led report on U.S. climate impacts warns of scorching 9 to 11°F warming over most of inland U.S. by 2090“), a larger and larger proportion of that 5.2 billion will be Americans.

In short, climate change produces ideal breeding grounds for mosquitoes and the diseases they carry in once-safe, once-temperate regions. This puts hundreds of millions of Americans and billions of people worldwide at increased risk of contracting dengue, among other diseases; in regions with weak medical services, they face the possibility of death.

Unless we shift course soon, “desperately fighting deadly mosquitoes” could become the next major green job. How about we act now, stop climate change at a minimal cost, and actually save lives?

Austin Davis is a summer intern at American Progress, working on climate, energy and clean economy issues. Austin is pursuing a BA in political science at Middlebury College.

19 Responses to Climate change helps spread dengue fever in 28 states

  1. David B. Benson says:

    Reminds me of too busy wrazzling alligators

  2. Phil Eisner says:

    I am a member of the Board of Health in my city and will bring up dengue fever and its mosquitos in our next meeting. I expect this will quicken their interest in global warming,

  3. Dano says:

    Next ‘suppressed’ report released by CEI/AEI: cooling actually increases the spread of dengue fever.

    This helpful tip to identify industry mendacicization comes to you courtesy of RIH, a 501C(3).



  4. Dan B says:

    One of my lifelong friends volunteered for the Peace Corps and was assigned to Tonga, the “Arkansas” of the Pacific.

    He contracted “breakbone fever” and survived. Barely.

    Little things will get us. Little things like Carbon molecules.

    Forget Speilberg. The coming challenges are extremely slow and stealthy. Don’t look behind that door you encounter 20 years from now. It’s your death warrant. It’s the warrant for all humanity.

  5. Richard Steckis says:

    I do not know what this NRDC is (it is not a US Govt. body) but the Centers for Disease Control do not seem to be breaking into a sweat over it.

    Just because a vector expands its range, does not mean that the disease ipso facto follows.

  6. Eli Rabett says:

    There was a NAS report on the relationship between climate change and health some years ago that looked into these issues and concluded that the effect of spreading the range of diseases could by handled but would require careful monitoring for the appearance of new diseases in other areas. Looks like this is being followed. It is something one has to pay attention to, but not get paranoid about.

  7. john says:


    If Dengue fever were the sole effect we had to worry about, I’d agree. Develope a vaccine, monitor its progress etc. Expensive; likely to kill more people each year than 911, but we could cope.

    But let’s throw in Malaria, rising sea levels and disposessed people (can you see New Orleans times 10?); record-making draughts; rampant wildfires; diminished food stocks; sterile oceans and completely devastated fish stocks; and killer heat waves — it all gets a bit more complicated.

    And I’m going to address this question to those who don’t trust government to be capable of doing anything right — in fact, if you are a typical denier it’s one of your central set-pieces.

    This may not apply to you, Eli, but just in case it does, here’s a question for you ( and if it doesn’t, I’d like to have a denier’s answer.)

    If you don’t trust government to do anything right, why are you willing to create havoc on an epic scale that only a government can respond to?

  8. I keep waiting. But the Bill and Melinda Gates Foundation still has not discovered global warming.

    Looking at their heavy investments in carbon fuel energy, it looks like they are mired in denial.

  9. Caution: I thought the headline was telling me that DF was spreading in 28 states, but actually, as you explain, it’s conditions favorable to transmission that are spreading, not necessarily the disease itself. Outbreaks of DF have so far been confined to areas near the Mexican border. (Almost every state has had cases from infected travelers, but that’s another matter.) Anyway, thanks for the info.

  10. Meagan says:

    In response to #5 and #9: With the vector present in 28 states, and travelers bringing the disease into every US state, sustained transmission of Dengue in the US becomes increasingly likely. For an example of where this has already occured, look at Chikungunya in Italy. The Aedes albopictus mosquito was reported to have spread into Italy as a result of warming climates by 1998. By 2007 there were sustained outbreaks of Chikungunya. A similar pattern of vector establishment followed by disease can expected for Dengue.
    However, it is interesting to note that one possible reason Dengue may not become established may be our incessant use of air conditioning: people who stay inside are not likely to be bit by mosquitos.

  11. TomG says:

    Meagan…just because you’re inside doesn’t make you safe.
    Ever own a dog? As in “A dog is always on the wrong side of a closed door”?
    My Shepherd, who thinks he’s German, has a close friendship with mosquitos and he’s not above introducing them to me, usually at night when I can’t see the little…
    My point is, air conditioning is a good barrier, but it’s not fool proof.

    Richard @ #5…
    I believe you’ve missed the point.
    Just because the disease is not currently present in this expanded range is meaningless.
    Before it couldn’t exist in this area, but now it can.
    Disease will always take advantage of an opening.

  12. gtrip says:

    “A survey of the past shows that war, pestilence and famine always have been related, sometimes one, and sometimes another being the cause, and the other two the effect. Where one of the trio has occurred the others, sometimes singly, but usually together, have followed.”

    “The primary cause of famine almost invariably has been the failure of food crops. This failure has often resulted from a variety of natural causes – long-continued drought, blasting hot winds, insect armies, earthquakes, severe and untimely frosts, and destructive inundations.”

    From National Geographic Magazine in its July, 1917 issue.

  13. gtrip says:

    Richard Steckis says:
    July 11, 2009 at 10:21 am
    I do not know what this NRDC is….Ever heard of google? It’s a hollywood funded save the world cuz the parties are boring group.

  14. Richard Steckis says:

    Meagan says:

    “The Aedes albopictus mosquito was reported to have spread into Italy as a result of warming climates by 1998.”

    I suspect the mosquito has always been present in Italy. If not A. albopictus then definitely A. aegypti. My reasoning for this is that Malaria was common in Italy for most of recorded history. It was common in Roman times and was not generally eradicated until the 19th Century through swamp draining and mosquito control programs.

  15. Nancy Oden says:

    The problem with mosquito scares is that Big Pharma will begin again pushing DDT and other poisons onto us. Much better and safer are:
    –staying inside at dawn and dusk when mosquitoes are most active;
    –covering up with long sleeves, long pants with rubber bands around legs, socks, wide-brimmed hat with bug net;
    –spreading exposed skin (face, neck, or wherever) with thick layer of cream or vaseline so they can’t bite;
    –eliminating standing water which does not contain fish or other mosquito larvae eaters;
    –understanding that we cannot stop what’s happening so learn to protect ourselves (as above) and live with them.

    – Nancy Oden, Jonesport, Maine

  16. Glenn Dorfman says:

    Is there anything that climate change is not responsible for?

  17. Meagan (#10) I was only arguing that the headline itself implied more than is currently the case.

  18. David B. Benson says:

    Glenn Dorfman — Oceans about fished out; Aral Sea dried up; vast expanses of degraded soils and denuded forests.

    Lota of way for humans to muck it up with envoking global warming.

  19. Meagan says:

    Just a quick point in response to Richard: Mosquitoes most definitely have been in Italy for millennia, but malaria is spread by the Anopheles genus of mosquito. Chikungunya is only spread by the Aedes genus. It was the Aedes genus that was invasive to Italy and brought Chikungunya; it is the Aedes genus that is now invasive to the United States.