Parts of the planet warm and cool during El Niho and La Nifia. And infectious diseases also wax and wane in step with the climate cycle. Take malaria shown to spike in northern Venezuela during cool, La Niha conditions. Or flu pandemics, which often follow months after La Niha sets in. Now researchers have linked another public health risk to El Niho climate cycling: poisonous viper bites. Their study area was Costa Rica where health centers keep rigorous records on snakebites. They compared nine years of those snakebite records including some 6,500 bites to climate data over the same period. And they found that snakebites were two to three times as prevalent in the hottest and coldest years of the El Niho climate cycle. Sounds counterintuitive, right you might expect the climate extremes to have opposite effects. But the researchers say in hot, dry years, plant productivity peaks, driving an increase in the number of rodents.