Global Warming

Climate Change Pushing Tropical Diseases Toward Arctic

Temperature changes around the globe are pushing human pathogens of all kinds into unexpected new areas, raising many new risks for people.

Among the most well-documented of these new threats is the spread of ocean-traveling Vibrio bacteria that can sicken or kill unsuspecting swimmers or shellfish eaters, even though these bacteria need warm water to survive.

Before 2004, for example, Alaskan waters were thought to be too cold to support enough Vibrio to cause disease. But around July 4 that year, aboard a small cruise ship, several dozen passengers got sick after eating oysters from the Gulf of Alaska—more than 1,000 kilometers further north than the previous northernmost Vibrio incident. The waters that summer around the oyster beds were 2 degrees warmer than they’d ever been.

Already in Europe, for example, the ticks that carry Lyme disease, once largely limited to the south, are finding new hosts as far north as Sweden. Some winters aren’t cold enough to kill the young nymphs, which also allows them to stick around another season. A similar issue has struck a region near Russia’s Ural Mountains, which has seen a 23-fold increase in tick-borne encephalitis in 20 years. Temperature changes have lengthened the tick season by half (the same problem is hammering moose). Meanwhile, the sandflies that host parasites that cause leishmaniasis, some varieties of which cause skin lesions or spleen and liver damage, are showing up in north Texas.

Evidence suggests, for example, that moisture changes could alter the spread of the soil-borne fungi that give rise to the American Southwest’s flu-like valley fever. Infections that aerosolize, like tuberculosis, can linger longer and perhaps be transported easier in regions of the world projected to become more humid. New research suggests the spread of blood-sucking kissing bugs that contain parasites that carry Chagas Disease may well help that affliction spread into North America. Already millions of people worldwide, mostly in South America, suffer from chronic Chagas, which can lead to life-threatening heart damage and stroke.