Climate Change Is Helping to Spread Deadly Viruses

The ebola outbreak stunned the world, as it rampaged across the globe, killing tens of thousands. But climate change may spark a whole host of similar, global epidemics, according to new scientific research.

Ebola and the West Nile virus are just two examples of the many diseases that have recently spread into unexpected places, as climactic fluctuations have pushed species into new environments, zoologist Daniel Brooks says in a paper published today in a British journal.

As animal and plant life have moved, so have the parasites attached to them — and those parasites can leap to new species much more easily than previously thought, Brooks told VICE News. When a parasite latches onto a new host organism, the organism is much more vulnerable to the novel pathogen.

"Climate change does result in species moving around, and with respect to pathogens those movements actually create an enormous number of opportunities for parasites to jump into hosts they've never seen before," Brooks told VICE News.

Previously, researchers claimed that parasites remained attached to one species only, but Brooks explained that parasites actually successfully moved to similar organisms. For example, a parasite linked to one particular rodent would readily hop to other rodents — which have had no chance to develop a resistance to the parasite.

Brooks, who specializes in reconstructing the genealogies of species, looked at the past 30 years of research in the field, and also tracked previous vector-borne diseases — including during the last Ice Age.

"These host switches don't happen at random. They're actually clumped at particular times," Brooks said of climate's effect on the spread of parasites. He explained that glaciers pushed plants and animals south, so parasites jumped to new hosts after the last Ice Age.

"There is an enormous possibility of diseases passing to new hosts," Brooks said. "It's going to intensify as climate change progresses."

One prime example of the phenomenon is West Nile virus, which wiped out a devastating number of songbirds, as the disease spread across the Western Hemisphere in the early 2000s, Brook explained. At the time, it was considered an acute disease, but then the songbirds developed a resistance to the virus. Still, West Nile has far from disappeared — it is just less obvious, and is now considered a chronic disease.

"Initially the disease is a problem, and then appears not to be a problem anymore, but the parasite never goes away," Brooks warned. "Pathogens move around a lot when they have the opportunity, and all of these pathogens have much greater capacity than we think. The planet is a minefield."

With diseases rippling across the globe at an increasing rate, Brooks emphasized the critical need for studying non-human species and their role in the spread.

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"As long as we think of ebola as a human-to-human problem, we're missing the possibility that if some non-human picks up ebola we never get rid of it," he said. "We need to pay more attention to natural history."

Salvatore Agosta, who has co-published papers in the field with Brooks, affirmed Brooks's claims, emphasizing that "there is a lot more flexibility for parasites" than previously thought. As organisms migrate amidst climate change, the potential for spreading increases, Agosta, an assistant professor at Virginia Commonwealth's Center for Environmental Studies, told VICE News.

A representative from the Center for Disease Control (CDC) told VICE News climate change was certainly impacting the spread of diseases — but that the details remained unclear.

Lyme Disease has already moved north due to climate change over the last several years, for example — but it has also spread further south, suggesting that other factors are at play, according to Ben Beard of the CDC.

"The simple statement is that changes of climate will affect the environment," Beard told VICE News. "What's more difficult is to say precisely where and how."

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Predicting new outbreaks both presents the greatest challenge, and often receives the least attention — creating a risky combination, John Carlo, the former chair of the Texas Medical Association's Council on Science and Public Health, told VICE News.

Heath care professionals understand how to respond to many disease outbreaks, such as the West Nile virus. But other illnesses, like chikungunya, have shocked the profession. Mosquito-borne diseases are on the rise in Texas, prompted by climate change, said Carlo.

And when the CDC faced budget cuts last year, Texas was hard-pressed to tackle its sudden influx of ebola cases, he noted.

"The first thing you want is a more robust capacity to deal with any emerging threats," Carlo told VICE News. "But any time you're dealing with low funding the first thing you cut is what seems unnecessary, and when you're dealing with the unknown that's the first thing cut."

Follow Meredith Hoffman on Twitter: @merhoffman