A ounce of prevention is worth a pound of cure. The tropical diseases are migrating towards the poles. As the globe warms, mosquitoes will roam beyond their current habitats, shifting the burden of diseases like malaria, dengue fever, chikungunya and West Nile virus. In 2009, dengue emerged in south Florida and infected more than 60 people. Another disease, Chikungunya, may also set up shop in the United States. The disease's name means "that which bends up" in the Makonde language in East Africa, since the afflicted are often contorted from joint pains. The disease spreads through mosquitoes, particularly the Asian tiger mosquito, an invasive species that is expanding from the southeastern United States and may reach as far north as New York. The annual first frost tends to kill off mosquitoes, ticks and flies, but warmer temperatures are delaying frosts and pushing the frost line farther north. That creates the potential for year-round disease transmission in some parts of the country.