The fear of climate change-driven, super-powered infectious diseases is real. As the recent viral (haha) New York magazine story on climate change doomsday scenarios articulated:
There are now, trapped in Arctic ice, diseases that have not circulated in the air for millions of years — in some cases, since before humans were around to encounter them. Which means our immune systems would have no idea how to fight back when those prehistoric plagues emerge from the ice.
Prehistoric plagues are worrisome enough, but what about your present day infectious diseases? What about Zika and Malaria? The prognosis is also grim: For every degree of temperature increase mosquitoes reproduce ten times faster. According to the World Bank, by mid-century around half the world’s population could be exposed to Malaria-carrying mosquitoes.
Scientists have caught on to these risks and are now studying how exactly a warmer planet will give rise to more infectious diseases. Now, the first large-scale assessment of the effects has found that the impact of climate change on the emergence and spread of infectious diseases could be even greater than previously thought.
Published in Scientific Reports, the assessment looked at how climate affects bacterium, viruses or other microorganisms and parasites that can cause disease in humans or animals in Europe.
By examining published literature on the 100 human and 100 domestic animal pathogens that have the largest impact on health in Europe, the researchers determined that nearly two-thirds of the pathogens were “sensitive to climate,” and that two-thirds of those have more than one climate driver, meaning “the impact of climate change upon them will likely be multifaceted and complex.”
Previous research has estimated only about half of pathogens to be climate sensitive.
According to the release, diseases spread by insects and ticks were found to be the most climate sensitive, followed by those transmitted in soil, water and food. Furthermore, pathogens that spread from animals to humans — known as zoonotic pathogens — were found to be more climate sensitive than those that affect only human or animals. Some three-fourths of emerging diseases are zoonotic, and thus may be more likely to be impacted by climate change.
“We found that emerging pathogens were more likely than those non-emerging to be associated with rain or climate change,” Dr. Marie McIntyre, who led the project at the University of Liverpool’s Institute of Infection and Global Health, told Project Earth.
McIntyre said that emerging means the diseases are increasing in incidence, expanding into new geographical areas or finding new hosts or vectors. She said some good examples of emerging pathogens in Europe include: Vibrio cholerae (the causative agent of cholera), Fasciola hepatica (which causes liver fluke in livestock), Bacillus anthracis (the cause of anthrax), and Borrelia burgdorferi (the cause of tickborne Lyme disease), as well as Zika virus and Chikungunya virus.
“When diseases emerge they become of high interest to those involved in public health and veterinary public health, and consequently to funders of research and a large media interest is generated,” said McIntyre.
The study also found that some taxa are more likely to be affected by climate change than others: For example, bacteria, fungi and viruses generally had fewer climate drivers compared to protozoa and helminths (parasitic worms).
“We found that the most common combination of drivers to which pathogens were sensitive was moisture and rainfall, but these are often omitted in models of climate change on disease, which often use temperature,” said McIntyre. “Our work suggests that many models which are used to predict future climate effects may be improved in the future as skill in projections for rainfall and moisture increases, but we’re not there yet”
The study’s authors state that evidence already suggests that climate change is allowing certain diseases to get to higher latitudes and altitudes, and that “the expectation must be that such effects will continue, and perhaps accelerate in future, as the global climate continues to warm and rainfall patterns change.”
According to the World Health Organization, there is already a global increase in infectious diseases underway — including such favorites as HIV/AIDS, SARS, and hepatitis C — due to rapid population growth and other modern lifestyle changes. Climate change will amplify these impacts, with the WHO stating that “changes in infectious disease transmission patterns are a likely major consequence of climate change.”
Clearly further study is needed.
“Now we have identified the scale of the climate problem, the next step of the work should be to comprehensively examine the actual impact of climate on each disease,” said McIntyre.