Threats from a warming climate come in extra large and very small packages: Mosquitoes Carry Yet Another Tropical Disease toward the U.S.

Cases of chikungunya fever have already spread across the Caribbean islands.

Feb 6, 2014 |By Dina Fine Maron, in Scientific American

It began last October, with a simple mosquito bite on the Caribbean island of Saint Martin. With that itch-inducing nip from an infected mosquito, a disease known for causing patients to stoop over in pain made its first locally acquired appearancein the Western Hemisphere. By mid-December, two dozen cases of the viral disease had been confirmed. More than 1,000 cases have since scattered across the Caribbean isles, inching ever closer to the U.S.

The disease—chikungunya fever (pronounced chik-un-GUHN-ya)—is named for its trademark overwhelming joint pain: In the Makonde language of southeastern Africa the word means “that which bends up.” There is no vaccine for chikungunya, but the virus is rarely fatal. It typically causes high fevers, joint pain, rash and headaches that last for about a week. In severe cases it leads to longer-term joint pain.

Risk that it could soon show up in the U.S. Virgin Islands or Commonwealth of Puerto Rico is “high” says Mark Fischer, a medical epidemiology with U.S. Centers for Disease Control and Prevention’s Arboviral Diseases Branch. “I think it’s very likely that this virus will further spread throughout the Caribbean or the Americas,” he says. That means the continental U.S. could soon be feeling the pain, he adds. And although the cold weather would afford some level of protection to some areas of the U.S. (because mosquitoes are less likely to be out supping on humans in the cold) that modicum of protection will disappear as the weather gets warmer. In fact, the spread of chikungunya in the Western Hemisphere could be poised to create a new normal. “This will move from country to country and could basically establish itself and become endemic in this part of the world,” Fischer says.

There are no guarantees about when, or even if, a massive chikungunya fever outbreak will happen. Consider the example of dengue, another virus transmitted by the same mosquito species. It has taken hold in some parts of the U.S., such assouthern Texas, but not in other areas, including Tucson, Ariz., where the conditions are perfect for an outbreak. Chikungunya outbreaks are equally hard to predict.

Whereas it is unnerving that chikungunya has landed on islands close to the U.S., that in itself doesn’t necessary increase the risk it will end up in this country. “I don’t know if we are at any greater risk now that it is in the British Virgin Islands than we were weeks ago when it was in Saint Martin,” Fischer says. It is not that mosquitoes will cross the ocean. Instead, chikungunya is most likely to spread with infected people hopping from island to island and to the mainland. So will it land here? We’ll have to wait and see.