Chikungunya, a highly infectious disease, may soon arrive in the U.S.

When Clare Rourke woke up one morning last March with a sore toe, she didn’t worry too much about it. She, her husband and their three daughters were living in Yogyakarta, Indonesia, for a few months as part of a family year abroad. She and her husband had traveled widely — through India, the Middle East and South America — and had never been seriously ill. And they took necessary precautions, making sure everyone in the family received the recommended vaccinations.

But by the middle of that day, Rourke was sicker than she had ever been before. “I hurt in so many places — my feet, hand, wrists, ankles, elbows, knees,” she says. “I actually remember thinking that I just might die.” Her joints were so swollen, hot and painful that she couldn’t rest her elbows on the bed. Her temperature rose to 104 degrees. “I felt like something was attacking me and I was seriously losing the fight,” she says. That night, two of her daughters also became achy and feverish, and within a few days, all three had rashes on their hands, legs and arms. They were infected with chikungunya, a virus originally from Central Africa.

The virus, transmitted by mosquito bites, was rampaging through Yogyakarta — part of an outbreak that has stretched across the Indian Ocean, India and Southeast Asia since 2005. Now it is roaring through the Western Hemisphere. In December 2013, the first locally transmitted case of chikungunya in the Americas was identified on the Caribbean island of St. Martin. As of mid-April, more than 25,000 cases had been reported across the region, from the Dominican Republic to French Guiana, on the northeast coast of South America.

Public health officials suspect the virus may already be in Puerto Rico, and they predict it will make the leap to the continental United States within months. “There’s nothing to stop this outbreak from continuing to spread,” says Lyle Petersen, director of the division of vector-borne diseases of the U.S. Centers for Disease Control and Prevention. Infections are likely to escalate this summer, when the Caribbean rainy season sets in and mosquito populations climb. Chikungunya seems poised to join a handful of tropical diseases — including dengue, Chagas’ disease and West Nile — that are spreading across the southern United States.

The good news is that the initial symptoms — sudden fever, rash, headache and aching joints — generally clear up within a week or two, and the disease is rarely fatal. So far in the Caribbean outbreak, six people have died from it.  

But there is no vaccine and no treatment. And as Rourke found out, many of those infected suffer from severe joint pain long after the initial illness. In the Makonde language of East Africa, chikungunya means “that which bends up,” and that’s exactly what Rourke did for months, hobbling about her house and leaning on furniture to support her. Even maximum doses of painkillers like ibuprofen made little difference. A neighbor, seeing her limp down the street, gave her a local remedy, a syrupy medicine, but that didn’t help either. Finally, steroids brought some relief.

It’s not known what percentage of people infected with the virus develop long-lasting joint pain. In an outbreak in 2005 and 2006 on the French island of Reunion in the Indian Ocean, about one-third of the population was infected, giving researchers a good opportunity to study the disease. Local physicians working with researchers at the Institut Pasteur in Paris followed one set of chikungunya patients who had been sick enough to be sent to the hospital, finding that about 60 percent still had significant arthritic pain three years later. People over the age of 35 and those with diabetes were more likely to be affected. “It’s going to make you feel awful for a long time,” says Kristy Murray, an infectious-disease specialist and associate vice chair for research at Baylor College of Medicine and Texas Children’s Hospital. “It’s really debilitating.”

Both of Rourke’s daughters got over their symptoms quickly, but it took three months for Rourke’s pain to ease and nine months before it was bearable. More than a year later, she still has some stiffness in one ankle and one hand but says she hardly notices; mostly, she’s grateful that the pain has finally diminished.

It’s not yet clear how widespread the virus could become in the continental United States. The strain of chikungunya spreading in the Caribbean is most commonly transmitted by Aedes aegypti, a mosquito species that can survive only in the warmest parts of the country, in southern Texas, Louisiana, Alabama, Mississippi, Georgia, Florida and South Carolina, as well as parts of southern Arizona and a few cities in California. That could limit transmission.

But in other outbreaks, the virus was carried by the Asian tiger mosquito, Aedes albopictus. This invasive species first appeared in Houston in the 1980s, hiding in a shipment of used tires. It is now found from Illinois to New York State. Researchers don’t know if the Asian tiger mosquito can efficiently transmit the strain of chikungunya circulating in the Caribbean. But if it can, the disease could easily travel as far north as New York City.

People who get chikungunya can be highly infectious because the virus reproduces very rapidly in the blood. A study of a small outbreak in northern Italy in 2007 that affected about 197 people suggests that just one infected person carried the virus from India.

Why are tropical diseases like chikungunya and West Nile virus now causing outbreaks around the world? It’s due in part to increasing travel and urbanization, say Murray and Petersen. Another reason might be climate change: Mosquitoes that used to be killed off by severe winter weather now survive farther north than before. “These diseases can’t take root if they don’t have the vectors to carry them, but now the vectors are thriving in places they never did before,” says Linda Marsa, author of “Fevered,” which examines how climate change will affect our health.

Because chikungunya is so new in the Western Hemisphere, few doctors have heard of it, says Murray, and they may not think to test patients for the virus. In an effort to catch an outbreak early, starting this month, Children’s Hospital in Houston will test all kids who show up at the emergency room with feverish symptoms for chikungunya as well as dengue and West Nile.

Murray urges people to protect themselves from mosquito bites even during the day, because that’s when the Asian tiger mosquito prefers to bite. Even though nobody has yet found the virus in the U.S., it could arrive any day, she says. “We have cruise ships coming in every day [from the Caribbean]. We have the vectors here and the perfect conditions for spread.”