Pediatrician Jennifer Halverson will never forget her 36th birthday.
The St. Paul native was volunteering at a maternity clinic in Port-au-Prince, Haiti. She felt great — she went to her job that day and then out to dinner with friends.
But when she got home and went to sleep that night in May, something didn't feel right.
"Then I woke up at 3 in the morning," she says, "and what struck me the most was that my shoulders were on fire. It was like I was being stabbed in both shoulders."
The pain quickly spread to all of Halverson's joints — her hips, her knees and elbows. Even her fingers and toes hurt.
Halverson also had a fever, a rash and painful sores in her mouth. When she flew home to Minnesota, the doctors confirmed what she thought might be true: chikungunya. Though the rash and sores quickly faded, and the illness is rarely fatal, the joint pain it causes can last for months. Halverson is still hurting — she says she still can't open jars.
A year ago, chikungunya didn't even exist in the Western Hemisphere. It was only found in Africa and Asia. But in October, the mosquito-borne illness cropped up on the island of St. Martin. Then it spread like wildfire.
The Pan American Health Organization reported Monday that over the past seven months, chikungunya has sickened more than a quarter-million people in the Caribbean. And the nasty virus has already started to trickle into the U.S.
So far, 112 travelers have brought chikungunya to 27 states, the Centers for Disease Control and Prevention said Tuesday. The disease hasn't yet spread beyond those travelers. But health officials think it's only a matter of time.
"Right now, we are worried about chikungunya in the U.S.," says Roger Nasci of the Centers for Disease Control and Prevention. "In fact, we expect that over the course of the next months or years — as this virus spreads through the American tropics, and we see more travelers coming into the U.S — we will see local transmission."
Why? Because many parts of the U.S. have the key ingredient for spreading chikungunya: a big black-and-white striped mosquito, called Aedes albopictus.
"Yeah, that's the Asian tiger mosquito that people notice when it's there because it bites during the daytime," Nasci says. "They're very aggressive and very noticeable because populations can be large."
The Asian tiger mosquito is common in the eastern third of the U.S. And its territory reaches as far north as Connecticut and New York City. The Aedes aegypti mosquito also transmits chikungunya. But this species is found mostly on the southern edges of the U.S.
There's no need to worry about chikungunya for this Fourth of July weekend, Nasci says. The risk for catching chikungunya in the U.S. is still very low — even if a case or two pops up in your county.
But if you're still worried, Nasci says there's an easy way to cut your risk further: Get rid of standing water in your backyard.
"These mosquitoes, they live in the water in your flower pot reservoir, the kid's toy that's out back and collects rainwater ... or that tire or bucket," he says. "So if you eliminate those containers, you're going to reduce the number of mosquitoes near your residency, which is going to reduce your risk."
And if the virus does get a foothold or two here in the U.S., Nasci thinks the outbreaks will likely be small and limited only to summer months. Even in Florida, mosquito populations go down during the winter.
There's something else Americans have going for them when it comes to stopping chikungunya: "We love air conditioning," he says.
So we spend a lot of time indoors, where mosquitoes — and chikungunya — can't get us.
RENEE MONTAGNE, HOST:
American health officials are watching out for a new mosquito-borne viruses that's making its way to the U.S. It's called chikungunya. It is currently sweeping through the Caribbean where it's already made more than a quarter million people sick this year. Here in the U.S., 27 states have reported cases. As NPR science reporter Michaeleen Doucleff reports, the question now is, just how big a health threat the virus will be.
MICHAELEEN DOUCLEFF, BYLINE: Jennifer Halverson will never forget her 36th birthday. She was volunteering at a maternity ward in Haiti, and she felt great. She went to her job that day and then out to dinner with her friends at night. But when she got home and got ready for bed, something wasn't right.
JENNIFER HALVERSON: And then when I woke up at three in the morning, the thing that struck me the most is my shoulders were on fire. It was like I was being stabbed in both shoulders.
DOUCLEFF: The pain quickly spread to all of Halverson's joints, her hips, her knees, her elbows - even her fingers and toes hurt.
HALVERSON: The pain itself was so severe that literally any movement - lifting my arms up, trying to change clothing, trying to lift the covers off of me in bed - was extremely painful.
DOUCLEFF: She also had a fever, a rash and painful sores in her mouth. She was supposed to go back home anyway, and when she got back to Minnesota, the doctors confirmed what she thought might be true.
HALVERSON: I knew right away that this was most likely chikungunya. The symptoms were just classic.
DOUCLEFF: That was about six weeks ago. The rash and sores have disappeared, but the joint pain is still there, and that's usually the case with chikungunya. It probably won't kill you, but the pain can last a long time. At this point in the story, you're probably going, chicken what? - because we've never really heard of chikungunya. Why should we? It didn't even exist in the Western Hemisphere a year ago. But late last year, the virus hopped its way over from the Philippines to the French part of Saint Martin. Then chikungunya spread like wildfire.
ROGER NASCI: The virus infected large numbers of people in many areas across the Caribbean and in the other regions of Latin America.
DOUCLEFF: That's Doctor Roger Nasci with the Centers For Disease Control and Prevention. He says that for infectious diseases, what happen in the Caribbean usually happens to the U.S. because about half of all air travel from the Caribbean ends up in the U.S. So far this year, about 110 travelers have shown up in the U.S. with chikungunya. The good news is the disease hasn't spread beyond these travelers. The bad news is that Nasci thinks it's only about a matter of time.
NASCI: Right now it's - we are worried about chikungunya in the United States. In fact, we expect that over the course of the next months or years, as this virus spreads throughout the American tropics and we see more travelers coming into the U.S. - that we will see local transmission.
DOUCLEFF: Why? - because many parts of the U.S. have the key ingredient for spreading chikungunya, a big black and white striped mosquito.
NASCI: Yeah, that's the Asian tiger mosquito that people notice when it's there because it bites during the daytime when people are out trying to enjoy their backyards, and they're very aggressive and very noticeable because the populations can be large.
DOUCLEFF: Nasci says there's no need to worry about chikungunya for this 4th of July weekend. For you to catch it here, you would have to be next to somebody who just brought the virus back to the U.S. Then a mosquito that bites them would also have to bite you. With only about 100 cases reported so far, the risk of this happening is very low. But if you're still worried, Nasci says there's an easy way to cut your risk further.
NASCI: These mosquitoes - they live in the water in your flowerpot reservoir, the kids toy that's outback that collects the rainwater or the water from your sprinklers, that tire or that bucket. So if you eliminate those containers, you're going to reduce the number of mosquitoes in your - near your residence, which is going to reduce your risk.
DOUCLEFF: And if the virus does get a foothold here in the U.S., Nasci thinks the outbreaks will likely be small and limited only to summer months. Even in Florida, mosquito populations go down during the winter. And, he says, there's something else Americans have going for them.
NASCI: We love air-conditioning.
DOUCLEFF: So we spend a lot of time indoors where mosquitoes and chikungunya can't get us. Michaeleen Doucleff, NPR News.
MONTAGNE: You're listening to MORNING EDITION from NPR News. Transcript provided by NPR, Copyright NPR.