Cholera, Other Illnesses May Spread with Climate Change

L’ARCAHAIE, HAITI – OCTOBER 28: A man suffering from cholera rests in bed at a rural hospital October 28, 2010, in L’Arcahaie, Haiti. Haiti, one of the poorest nations in the Western Hemisphere, has been further unsettled by an outbreak of cholera which has killed at least 300 people so far. The epidemic has affected the central Artibonite and Central Plateau regions with 3,612 cases so far on record. While authorities believe the outbreak is contained, they believe it has not yet peaked. There is also fear that the deadly diarrheal disease could migrate to the sprawling camps for the hundreds of thousands of Haitians displaced by the earthquake. (Photo by Spencer Platt/Getty Images)

Infectious-disease specialists are concerned that climate change is contributing to the spread of certain diseases, including the germs that cause cholera and other diarrheal illnesses.

Data now suggest that the locations where certain pathogens are found have changed, said Dr Glenn Morris, the director of the Emerging Pathogens Institute at the University of Florida. Morris gave a talk here today (Feb. 16) at the Climate & Health Meeting, a gathering of experts from public health organisations, universities and advocacy groups that addressed the health impacts of climate change.

Officials with the Pan American Health Organization warned about a possible surge in cholera cases because of the widespread flooding caused by Matthew. Haiti’s cholera outbreak has killed roughly 10,000 people and sickened more than 800,000 since 2010

Pathogens tend to live in places that have ideal sets of conditions, Morris said. For example, these bugs may have evolved to function best within certain temperature ranges, he said. And as climate change occurs and global average temperatures rise, researchers are beginning to see some indications that the areas where certain pathogens can live are shifting, he said.

“We are seeing the spread of pathogens to new ecological niches,” Morris said.

And the pathogens that live in water are among scientists’ top concerns, Morris told Live Science.

Temperature anomalies (in degrees Celsius) of various regions around the world in August 2014.
Credit: NASA

Vibrio and algal blooms

One group of bacteria, called Vibrio species, are particularly well-studied, Morris said. Vibro bacteria are responsible for cholera and other diarrheal diseases. Although cholera can be treated by rehydration according to the World Health Organization, the disease can still be fatal if not treated quickly enough.

Vibrio bacteria live in seawater, and with sea temperatures rising, scientists have recently observed a northward shift in the bacteria’s range, he said. In addition, diseases such as cholera often spread following events like flooding, which may become more common with climate change, Morris said.

Boats going through an algal bloom on Lake Erie near Toledo, Ohio.

Other waterborne diseases can come from harmful algal blooms, which are caused by toxic forms of algae, Morris said. Algal blooms have been linked to illnesses such as ciguatera, which people get from eating fish that contain toxins produced by the algae Gambierdiscus Toxicus, according to the Centers for Disease Control and Prevention. Another illness linked to harmful algal blooms is amnesic shellfish poisoning, which is caused by eating contaminated shellfish.

Warming seas are breeding cholera-causing bacteria in the north Atlantic, poisoning shellfish and other seafood.

These harmful algal blooms are showing up in places where they previously didn’t occur, including the Pacific Northwest, Alaska and Maine, Morris said.

This dead fish suffocated during the massive algae bloom in Lake Erie in 2011.
Toxic algal bloom in California’s Klamath River
An Aedes aegypti mosquito, the chief vector of Zika virus.

But what about mosquitos?

Morris noted that there have also been some concerns about mosquito-borne diseases, because of evidence suggesting that certain species of the insect are moving farther north than they used to. But it’s unclear what impact this will have in the long term, Morris told Live Science. He noted that in developed countries, including U.S., many aspects of homes help protect people against mosquito bites, such as the use of window screens and air conditioning.

While the illnesses Morris noted in his talk are all known diseases, they can still pose public health challenges when they move into parts of the world where they haven’t occurred before, he said.

Mosquito larvae: Increased rainfall can create stagnant pools of water where mosquitoes breed
Copyright: Flickr/NOAA Photo Library

“We’ve always thought about tropical areas as having particularly significant problems with infectious diseases,” but “we’re starting to see some greater indications that those diseases may be creeping up here” in the U.S., he said.

Morris said that the U.S. can handle those diseases, but the bigger concern is that pathogens are always evolving. Microorganisms may be able to change over time, “and increasingly take advantage of conditions that may not have been present before,” he said.

Read the full article here:

Did you know?

Read how extreme weather contributes to the spread of diseases:

A fisherman cups algae-choked water from China’s Chaohu Lake in 2009.
Two people row their way across algae-infested Chaohu Lake, China, in a 2009 picture.
Fingers of sediment and green swirls of algae are visible in Lake Erie on March 21, 2012.

Learn more about Algal blooms:

Leave a reply!

  1. What does the rise in sea temperatures (an effect of climate change) directly affect the health of humans?
  2. Why are temperate countries like the USA starting to be more concerned about mosquito-borne diseases?
  3. Why is eating shellfish becoming riskier with rising sea temperatures?

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