The patient showed up at the University of Miami Jackson Memorial Hospital feverish and hobbled by joint pain, a rash spreading across her face, and was presumed to be suffering from lupus or severe rheumatoid arthritis.

But in talking to the middle-aged woman last week, doctors realized that her symptoms and recent history of travel to the Dominican Republic added up to a different diagnosis: chikungunya, an infectious disease carried by the same mosquitoes that spread dengue fever.

Chikungunya (pronounced chick-un-GOON-ya) has plagued other parts of the world—particularly Asia and Africa—for decades, becoming more prevalent in recent years. But it arrived in the Caribbean only in December and has already infected as many as 250,000 people there.

The virus is generally not lethal and can't pass from person to person. But the pain it brings can be horrible—some who have weathered its wrath have said they wished the virus had killed them. In rare cases, the agony can last for months or even years.

Public health officials in the Caribbean are struggling to contain the outbreak, in part because of the difficulty of limiting mosquito breeding grounds and because the disease is so new to the area.

Paola Lichtenberger, director of the Tropical Medicine Program at the University of Miami, says she is sure the epidemic is more widespread than official numbers suggest simply because making the diagnosis is so difficult.

Public health officials in the U.S. and around the world, meanwhile, are tracking cases carefully and encouraging people in affected areas to take precautions to avoid infections and to clean up areas of standing water. Airports in ten major American East Coast cities with Caribbean-bound flights have posted warnings to passengers about chikungunya.

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So far, 73 American travelers have brought the disease home from abroad and another 15 have been infected by mosquitoes in Puerto Rico and the U.S. Virgin Islands, though it hasn't yet reached mosquitoes in the continental United States.

But it's only a matter of time before that happens, according to Lichtenberger, who has helped treat three chikungunya patients since the outbreak began.

"I'm pretty sure we're going to have cases here, if we already haven't had them," she says.

Coming to America

So far, the Dominican Republic has been hardest hit, with 135,000 suspected cases; Guadeloupe comes next with 40,000, followed by Haiti with 39,000 and Martinique with 35,000.

"The whole Caribbean is just full of it," Lichtenberger says.

Doctors who had never seen the disease until six months ago struggle with proper diagnosis, she says, especially because chikungunya can look a lot like influenza or dengue—and can even occur together with dengue.

Lichtenberger expects more cases in the continental United States soon.

Someone from the Caribbean who has long planned a vacation or family visit to the U.S. isn't going to cancel just because mom, dad, or junior feels lousy, Lichtenberger says. If the sick person gets bitten by a mosquito in the U.S., the virus can easily get transmitted.

That's why it's important for sick people to take precautions to protect themselves from further mosquito bites, she says: not for their sake, but for others'.

But Mark Heise, who studies the genetics of disease susceptibility at the University of North Carolina in Chapel Hill, says chikungunya probably won't spread too far in the United States.

"It's something we should be concerned about, but I don't think people need to panic about it either," he says.

Heise looks at the transmission of dengue as an indicator for how chikungunya is likely to spread. Dengue fever is a major problem in the Caribbean and South and Central America, and there are sporadic cases on U.S. soil, "but it isn't a major public health threat."

The type of mosquito that has most often spread chikungunya, Aedes aegypti, does not live in the United States, says Stephen Morse, a virologist and professor of epidemiology at the Mailman School of Public Health at Columbia University in New York.

But its cousin Aedes albopictus, also known as the Asian tiger mosquito, lives as far north as Chicago and is also believed to be able to transmit chikungunya.

The virus tends to burn itself out in a particular community because it strikes so many people so quickly, Morse says. It leaves them with immunity that can last years or even a lifetime.

View Images A health worker examines a patient during a medical brigade last month to detect cases of chikungunya at a school in El Salvador. Photograph by Jose Cabezas, AFP/Getty

No Vaccine, No Meds

Chikungunya got its name from the phrase "which bends up" in the local dialect in Tanzania where it was first identified in the early 1950s. The term described the posture of someone with the disease, bent over with pain.

Most victims suffer extreme joint pain for 5-12 days, making it hard for them to grasp things with their hands or put weight on their legs. The pain usually subsides by the two-week mark, but a small number of patients "continue to have sporadic bouts of joint pain, and we really don't understand why that is," Heise says.

People middle-aged and older and those with preexisting medical conditions tend to suffer more than children and young adults, says Heise, whose research focuses on why the virus replicates in joints and why it causes an overreaction of the immune system.

There is no vaccine or medication that can change the course of the disease, though patients are given painkillers and told to drink a lot of fluids, Morse says.

To avoid getting chikungunya while staying in affected areas, take the usual precautions against mosquitoes: Wear long sleeves, use repellents, and keep outside areas free of standing water where mosquitoes can breed.