Climate change might have a nasty bite. A new study on snakebite rates in Costa Rica has found that the bite rate shoots up during El Nino – at both the hot and cold parts of the cycle – and that the problem disproportionately affects poor, rural populations.

The findings, described in the journal Science Advances, reveals another complexity of the effects of climate change – both the effects it has on animal populations and the way it affects human disease, in the context of socioeconomic disparities.

Climate change isn’t just about warming temperatures and rising sea levels. It also sets in motion complex consequences that may have unforeseen impacts on ecosystems and human health. Research shows that climate change alters patterns of disease transmission. But for this paper, the researchers wanted to focus on another affliction: snakebites.

“Snakebites,” said lead author Luis Fernando Chaves, an ecologist at the Nagasaki University Institute of Tropical Medicine in Japan, “don’t get the attention they deserve, even though they are a major problem.”

After all, snakebites affect 2.5 million people around the world annually, and 400,000 of those people suffer serious medical consequences (such as nerve damage or amputations) and 85,000 of them will die.

And because snakes are ectothermic, or coldblooded, they rely on the environment to regulate their body temperature, which means their behavior might be highly influenced by the changing weather patterns induced by climate change.

“It can be argued that snakebite envenomation is a neglected tropical disease,” the study authors wrote.

The scientists focused on Costa Rica, which has a universal health care system, and where snakebites might be less underreported, partly because reporting snakebites is mandatory. Most snakebites in Costa Rica are chalked up to one particular species of snake, the terciopelo Bothrops asper.