Climate Change Playing a Role in Cross-Species Viral Transmission to Humans


As if the known repercussions of climate change aren’t enough, here’s one more. A study published in Nature called “Climate change increases cross-species viral transmission risk” is both fascinating and scary.

At least 10,000 virus species have the ability to infect humans but, at present, the vast majority are circulating silently in wild mammals. However, changes in climate and land use are shifting the playing field and in the process placing humans more at risk.

Researchers say, bats account for the majority of novel viral sharing and are likely to share viruses along evolutionary pathways that will facilitate future emergence in humans. It turns out a couple of degrees in temperature do make a difference.

The study establishes a macroecological link between climate change and cross-species viral transmission. Actually, an example of this may be the recent global pandemic of COVID-19 caused by SARS Coronavirus2 if it was caused by bats (which continues to appear likely). Another example is the explosion of ticks in the U.S. which has caused a huge spike in tick diseases with Lyme leading the way.

Even ticks have their place in the environment, so humans first inclination to “destroy the enemy” isn’t at all a solution. For example, some want to annihilate bats, due to their apparent increasing ability to spread illness to humans. However, if bats die, we lose essential pollinators and mosquito killers. Aside from humans, the most dangerous living things on the planet are mosquitos.

The study also showed that aside from mammals, birds increasingly are a reservoir for zoonotic viruses (viruses passed from animals to humans). In part, birds because of changing bird migration patterns in a warming world. Similarly, with amphibians facing disproportionately high extinction rates due to a global fungal panzootic, and emerging threats such as ranavirus causing conservation concern, pathogen exchange among amphibians may be especially important for conservation practitioners to understand.

And the problems don’t stop on land, increasingly marine mammals are an important target for zoonotic threats and even fish, particularly fish we eat. Pathogens eventually find their way into the water table, as exemplified by SARS CoV2 which causes COVID-19.

Incidentally, researchers involved in this study support the likely prospect that the progenitor of SARS-CoV-2 probably originated in southeast Asian horseshoe bats and may have spread to humans through an as-yet-unknown bridge host. Tracking viral spillover into humans is paramount, and so is the proactive monitoring of viral transmission among wildlife species.