If you read Newsweek or CNBC this week, you may be under the impression that one of the primary drivers of the Ebola outbreak in Africa is climate change. It is not.
According to three veteran epidemiologists who study how climate impacts disease spread, there is currently no scientific evidence that suggests a climate link to the current Ebola outbreak, which has so far claimed the lives of at least 1,200 people. Prematurely reporting on this link is harmful, they say, because it undermines good research that is being done on the growing link between global warming and other types of infectious diseases, such as malaria and cholera.
“Because the whole climate change debate has been so controversial, we’ve got to be doing solid science in that area,” said Andrew P. Dobson, an ecology and evolutionary biology professor at Princeton University who has been researching infectious disease spread and its relation to climate change since 1988. “If people start saying inflammatory things, it just messes up the whole funding arena for everybody else.”
Both Newsweek’s story, titled “Ebola and Climate Change: Are Humans Responsible for the Severity of the Current Outbreak?“, and CNBC’s story, titled “Is climate change key to the spread of Ebola?”, quote scientists from the non-profit EcoHealth Alliance to suggest that the virus could be worsened by a gradually warming earth. CNBC’s story in particular notes the theory that the Ebola virus is spread to humans via infected fruit bats. Climate change could cause those bats to have more babies, the story said, or could cause humans to come in contact with bats more frequently as drought dries out agricultural land, sending people into the forest for food.
But Jason Rohr, who studies disease ecology at the University of South Florida, said those claims are “irresponsible” to make because they’re not yet backed up by peer-reviewed research.
“The evidence is incredibly weak,” he said. “There’s a difference between weather patterns affecting an infectious disease and actual climate change impacting a disease. Weather patterns are going to occur on a much smaller time scale, whereas climate change, you need to link it to a long-term pattern. We’ve had so few [Ebola] outbreaks that we can’t yet make those claims.”
A. Marm Kilpatrick, who studies the ecology of infectious diseases at the University of California Santa Cruz and used to work for EcoHealth, also said scientists lack the long-term data to make those claims with confidence. While EcoHealth did not return ThinkProgress’ request for comment, Kilpatrick said he spoke with EcoHealth president Peter Daszak about the quotes given to CNBC.
“They asked him, ‘Could climate have influenced transmission of that disease,’ and the answer is sure,” he said. “We could all come up with stories about how that could have happened, but is there any actual evidence for that at all? The answer is no, and if you said, what do you think are the most important things leading to additional spill-over of Ebola from bats to people, none of us would mention climate change.”
“Climate change still influences Ebola, it influences everything,” he added. “It’s just that if you had to spend money on research efforts, it’d be more valuable to investigate other factors first.”
What scientists do have the data to claim confidently is that the spread of Ebola in humans may begin when people eat or otherwise come into contact with bats, apes, and other wild animals. This generally happens in undeveloped countries where health care is poor — another reason why the disease spreads so easily from human to human.
To fight Ebola, Dobson said, scientists must find out more about the basic biology of Ebola itself, and the immunology of bats, which he said seem to be reservoirs for a lot of infectious diseases. In addition, bringing better health care education and infrastructure to the places infected would do a world of good, he said.
Though Ebola in its current state is not cause for climate-related concern now, there are other, more prolific infectious diseases that stand to worsen in a warming world and are far more deserving of our attention in that context, Dobson said.
“We should be worried about climate change for other diseases,” he said. “Malaria, dengue fever — where the development time of the pathogen is very dependent on temperature, and the abundance of the mosquitoes is dependent on rainfall.”
Both vector-borne diseases — like those transmitted by mosquitoes — and water-borne diseases have a more solid scientific link to climate change and need to be researched more because of it, Dobson said. Because mosquitoes’ presence and lives are predominantly dependent on temperature, research funding needs to be dedicated to both the developmental time of diseases in the mosquitoes and the length of time the mosquitoes live for in hotter temperatures, he said. For waterborne diseases like cholera, Dobson said more research needs to be done about how rainfall patterns are going to be impacted by climate, and that needs to be paired with long-term hospital records to analyze how the two are dependent.
Diseases that look as though they have stronger connections to climate change are showing their faces throughout the United States. A mosquito-borne virus called chikungunya that’s been spreading throughout the Caribbean islands over the past year has made its way to U.S. soil, causing fevers, headaches, and joint swelling. The rise of that disease could be driven in part by climate change, which is increasing temperatures and moisture levels in the U.S. and ultimately facilitating a better environment for the type of mosquitoes that carry the virus.
In addition, the warm-water-dwelling, flesh-eating bacteria Vibrio vulnificus has infected more than a dozen people in the U.S. this year, some of whom have died. Even barring any studies connecting Vibrio and climate change specifically, a 2011 report from Climate Change and European Marine Ecosystem Research, a group of 17 European marine institutes, drew connections between climate change, the increasingly warm ocean waters, and the spread of water-dwelling bacteria like Vibrio.
This story has been updated to correct the person Mark Kilpatrick spoke with at the EcoHealth Alliance. He spoke with EcoHealth president Peter Daszak, not executive vice president William Karesh.