Rising Temperatures May Mean More Infectious Diseases

Professor Camilo Mora was bitten by a mosquito while visiting Colombia in 2014. It gave him the chikungunya virus and his joints still ache today. The professor now blames a warming world. 

He published a study this week with his colleagues at the University of Hawaii. They canvassed tens of thousands of studies to analyze the global impacts of climate change on infectious diseases that affect humans. 

This study revealed that almost 220 infectious diseases had become greater threats because of climate hazards.  

“Systems have been evolving for millions of years and now humans have come along and changed things,” Mora said. “We are punching nature, but nature is punching us back.” 

The study focused on more than 3,200 scientific works, and it is considered to be one of the most thorough examinations of climate change’s overall impact on diseases worldwide. 

Jessica Leibler is an environmental epidemiologist at the Boston University School of Public Health. She said, “It’s only in the recent past of infectious disease research that we really focus in on climate change as a driver of infectious disease.”

She also noted that infectious diseases are driven by what’s going on in our environment.

Mora’s team examined the effects of 10 climate hazards on 375 infectious diseases. They discovered more than 1,000 ways that climate change encouraged disease transmission. In fact, rising temperatures were the most significant driver of pathogenic diseases, followed by precipitation, floods, and drought.  

Warmer Temperatures Mean More Diseases Are Spreading

The culprits spreading the infectious diseases to humans were animals such as mosquitoes, snakes, birds, and rodents. 

An example of this is the Vole. It depends on snow cover for their winter home. But diminishing snow-packs have caused the creatures to seek shelter inside people’s homes, where they have been documented transmitting hantavirus. 

“Climate drives habitat change and disruption around the world. That also brings humans into contact with animal species in ways that we were not in contact with them historically, or haven’t been in the recent past,” Leibler said. “Our recent pandemic is an example to the extent that the leading hypothesis is that bats might have played a role.”

Higher temperatures have increased the presence of ticks, fleas, and mosquitoes. This has led to an increase in infections like the West Nile virus, Zika, and dengue fever. 

“Mosquitoes are obviously the big one that cause a tremendous amount of mortality internationally,” Leibler said.

Higher temperatures also increase the likelihood of survival for diseases that spread through food, water, or air. Fecal pathogens including E. coli or salmonella can get into drinking water after a flood or hurricane.

“There’s a good deal of evidence that as temperatures rise, it’s more likely that different sorts of pathogens will be present in drinking water globally,” Leibler said.

And hazards related to the climate can put stress on the human body which can make people more susceptible to infection. 

“What happens with warming countries in particular is that drought, because it undermines nutrition and increases malnutrition, compromises our body’s ability to fight infection,” said Amir Sapkota who is an epidemiology and biostatistics professor at the Maryland Institute for Applied Environmental Health. 

The study from Mora is raising concerns about the “Pandora’s box” of new pathogens that the world could face. Some have indicated that in the Arctic Circle, there are ancient pathogens in the bodies of animals frozen beneath permafrost that have started to re-emerge. Scientists traced a 2016 anthrax outbreak in Siberia to buried prehistoric animals that were exposed in the midst of a heatwave. 

“Melting permafrost may expose pathogens that are frozen in time,” Sapkota said. “We don’t even have any idea of what they are and what they would be like if they were to infect us today.”

Just in case you didn’t have enough in our crazy world to worry about!