In autumn 1885, just 46 years after the city was founded, the residents of Austin, Texas, began to feel sick. They developed a chill, followed by a swooping fever. They vomited, broke out in rashes, and felt an agonizing pain behind their eyes and in their bones. Weeks and even months later, the pain meant that they were unable to work. In a city with a population then of just 22,000 people, 16,000 became ill.

They weren't alone. Similar outbreaks occurred in Savannah, Georgia; Charleston, South Carolina; and Galveston, Texas. The disease was called dengue fever, or the "bone-breaking disease", and it caused outbreaks every 10 years until the 1940s. Then, during World War II, programs eradicated the mosquito population that carried the infections, and the disease was wiped out in the United States.

The problem is that dengue fever remains endemic in many portions of the world. Ranked just behind malaria as the worst mosquito-transmitted disease, dengue fever infects around 100 million people annually and causes 500,000 deaths. Formerly in just nine tropical countries, it now regularly appears in 100. And, well, it's back in the United States. In the new millennium, outbreaks have been recorded in Key West in 2009 and 2010, Brownsville, Texas in 2005, and Hawaii in 2001. In Hawaii, 122 people were infected. In Key West, new infections persisted well into the winter, when local mosquitoes should have been knocked out. Worse yet, the strain in Key West was not an imported one obtained from a tourist to or from a tropical country; it was a local one. Even now, in Key West, the disease keeps cropping up.

Dengue fever is of particular concern because of the way the disease makes its mark in a victim. For two weeks, the victim can carry and spread the virus without even knowing. In addition, if the victim has one type of dengue fever and contracts a second strain, even years later, it increases their risk of developing the worst form of the disease - dengue hemorrhagic fever. The disease disrupts patients' circulation, sends them into shock, and carries a death rate of 1 in 5.

Unfortunately, the United States could certainly have a nationwide epidemic on its hands. It has imported strains of the virus, especially through plane travel. It has two strains of mosquitoes, Aedes agypti, the more common vector, and Aedes albopictus, a less efficient transporter but which can survive winter and drought. Because the country has not seen the disease in years, it also has no immunological resistance to it. With climate change, too, it is possible that dengue could move farther north. There is no vaccine for it either, so the only protection is to wear repellant and avoid standing pools of water.

Barring some unseen factors, experts all agree that dengue fever is coming.

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