It started with a nagging pain in his wrists.

Gabriel S. Abromovitz, 32, an American who lives in Haiti helping to rebuild hospitals, thought his muscles ached one day in May because he had overdone it at the gym. He wondered if he was starting to get carpal tunnel syndrome from overusing the computer.

When other workers got sick, one of them passed along a fact sheet from the United States Centers for Disease Control and Prevention about an illness sweeping the Caribbean: chikungunya.

“I thought it was something related to chicken,” he said. “I was wiped out. It felt like a strong flu with aches and joint pain. My whole body was covered in red bumps.”

Mr. Abromovitz is among at least 800,000 people this year in the Caribbean and surrounding nations who contracted the chikungunya (pronounced chik-en-GUN-ya) virus, a mosquito-borne illness similar to dengue, which causes fever and muscle pain that is sometimes severe. It is rarely fatal, but some people suffer debilitating muscle pain for months or years.

Chikungunya was spotted on St. Martin in December 2013 and quickly spread across the islands. Although common in Asia, it was the first time the painful disease was detected in the Western Hemisphere. Now, experts say, it’s here to stay and has become an important issue for governments in tourism-heavy countries to tackle.

“Now I’d say about 40 percent of the ­people I know have gotten it,” Mr. Abromovitz said. “If you are going on vacation, I would recommend using DEET as opposed to taking your chances. Even if you’re only staying a week, I think you would have a chance of getting chikungunya.”

He recovered completely within two weeks, but saw co-workers affected more seriously.

First discovered in Tanzania in 1952, the disease has a name that means “that which bends up” in the Kimakonde language of Mozambique. It has sickened people in more than three dozen countries, including popular tourist destinations such as Martinique and the Dominican Republic. Some of the smaller islands, such as Guadeloupe and St. Barthélemy, were hit particularly hard, a sign that those nations may be over the peak.

Nearly 1,500 travelers to the region, often people visiting their families in the Caribbean, brought the disease back to the United States this year, according to the C.D.C. Before the Caribbean epidemic, the United States saw only about 30 cases a year, and those were usually people returning from Asia. After nearly 300 people in Florida brought the disease home this year, the state wound up with 11 locally transmitted cases — a first for the United States.

The C.D.C. has issued a “watch” alert for the Caribbean, which means tourists should take normal precautions.

Hugh Riley, secretary general of the Caribbean Tourism Organization, noted that “only a fraction” of the 45 million visitors who went to the Caribbean by air and cruise ship last year fell ill, and “they all have recovered.”

“The first thing the tourism industry did about chikungunya was to get the facts and the recommended procedures from the Caribbean Public Health Agency on how to protect both our citizens and our guests,” Mr. Riley said in a statement to The New York Times. “Our health officials are very actively engaging local communities to destroy mosquito breeding sites in order to reduce and eventually eliminate new cases of the virus. The aggressive program includes fumigation and getting rid of stagnant water and cleaning up the surroundings.”

Jeff Vasser, director general and chief executive of the Caribbean Hotel & Tourism Association, said that many hotels are providing their guests with repellents as a precautionary measure.

“Since the virus is spread by mosquitoes, we continue to encourage visitors to protect themselves from mosquito bites by using long-lasting repellents containing DEET, Picaridin, oil of lemon eucalyptus, or IR3535 on exposed skin,” Mr. Vasser wrote in a statement.

“The good news is that according to our local hotel association executives, across the Caribbean there have been few guest cancellations at hotels, and we are happy to see that the number of new cases of chikungunya has leveled off,” Mr. Vasser said.

Outdoor events, such as the World Creole Festival in Dominica, took place without outbreaks, and the Barbados Food & Wine and Rum Festival, which takes place in late November, is scheduled as planned, Mr. Riley said.

Lyndon Taylor, a spokesman for the Jamaica Tourist Board, said hotels are fumigating as often as five times a week, and have equipped rooms with vape mats. And in Puerto Rico, visitors to El Yunque National Forest are now greeted with posters that tell hikers how to prevent the virus.

Carnival Cruise Lines has included such information — including tips like putting on sunscreen before repellent — in the shipboard newsletter distributed daily to passengers.

Sandals and Club Med resorts did not respond to several requests for comment about what measures are being taken at their properties.

Kate Richardson, a spokeswoman for the St. Martin Tourism Ministry, said cleaning and awareness campaigns intensified in ­July. St. Martin, a country of just 33,000 ­people, had 4,240 suspected cases this year.

The last few months have recorded sizable decreases in the number of cases, Ms. Richardson said. But experts note that although some nations are past the worst of it, the illness tends to become more common during rainy season, which is approaching.

Dr. C. James Hospedales, the executive director of the Caribbean Public Health Agency, said the islands that were affected first, like St. Martin and Dominica, seem to be “over their peak, but not over the problem.” Based on past epidemics, experts predict this wave will take about 18 months to wind down.

The disease hit the region hard because it was new there, and no one had immunity.

“We predicted there would be widespread transmission, and that’s what’s happening,” Dr. Hospedales said from Trinidad. “This disease entered late last year, and now it’s spread to just about all Caribbean countries.”

The illness affects people differently. Children get over it quickly, but up to 20 percent of the people who contract it, particularly the elderly or people with chronic illnesses, are crippled with pain that is difficult to treat, he said.

“For a day or two many people describe extreme pain,” Dr. Hospedales said. ” ‘I’ve never had anything like this in my life.’ I can’t tell you how many times I have heard that sentence. Or, ‘I’d rather have 10 babies than chikungunya.’ “

PROTECTING YOURSELF

Dr. J. Erin Staples, a medical epidemiologist with the Centers for Disease Control and Prevention, says tourists should pick hotels with good screens or air-conditioning. “One of things about these mosquitoes is that they like to bite during the daytime,” Dr. Staples said. “People need to be diligent. People heard messages about West Nile that warned about mosquitoes at dusk and dawn. This is slightly different messaging.”

There is no vaccine or treatment, so that means the only prevention is to guard against mosquitoes. Experts offer these tips:

­- Wear repellent with a high percentage of the active ingredient.

­- Avoid products that combine sunscreen with repellent.

­- Wear long sleeves or specially treated clothing.

­- Be particularly mindful in the mornings, because the insects that transmit chikungunya — Aedes aegypti and Aedes albopictus mosquitoes — tend to be daytime biters.

­- People with arthritis, serious underlying medical conditions, the elderly and women who are late in their pregnancies are considered to be at higher risk for serious symptoms and should discuss their travel plans with a doctor, the C.D.C. says.

­”The message is to take extra precautions to avoid being bitten,” Dr. C. James Hospedales, the executive director of the Caribbean Public Health Agency, said. “By all means come and enjoy yourself. The vast majority of visitors will have a perfectly fine holiday and enjoy themselves. Some folks will get this; that is true. A minority.”