Haiti is dealing a deadly virus called chikungunya, a rarely fatal but intensely painful mosquito-borne virus that has spread rapidly through the Caribbean and parts of Latin America after local transmission first started in tiny French St. Martin late last year, according to The Associated Press.

Haiti is proving to be particularly vulnerable because so many people live packed together in rickety housing with dismal sanitation and surrounded by ideal breeding grounds for the mosquitoes that carry the illness, the AP reported.

"Chikungunya has been merciless in Haiti. Lack of basic infrastructure, poor mosquito control measures, and deep social and economic disparities hampered prevention and treatment efforts," says a new report on Haiti's epidemic by the Igarape Institute, a Brazil-based think tank, according to the AP.

Since the virus was first documented in Haiti in May, there have been nearly 40,000 suspected cases seen by health workers, according to the Pan American Health Organization, the AP reported. The only places with higher numbers are the neighboring Dominican Republic and Guadaloupe.

The U.S. Centers for Disease Control is now assisting Haiti's health ministry to confirm new cases, but statistics are notoriously unreliable in Haiti, and public health experts say the number of people with the illness is unknown, according to the AP.

In Haiti, it's gotten so bad so quickly that many people are resigned to catching the virus known in Creole as "kaze le zo," or "breaking your bones," for joint pain so intense some patients can barely walk or use their fingers for days, the AP reported. There is no vaccine and the only treatment is basic medication for the pain and fluid replacement for dehydration.

Painful symptoms of chikungunya generally dissipate within a week and people develop immunity after getting infected, but some patients can develop severe and even life-threatening complications including respiratory failure, according to the AP.

It can also contribute to the deaths of people with underlying health issues, Just last week, former Haitian President Leslie Manigat died after a long period of illness and a deputy secretary of his political party said his condition might have been complicated by a recent bout with the virus, the AP reported.

Health officials in North Carolina, Nebraska and Indiana reported confirmed chikungunya cases in June, along with Tennessee, which has suspected cases, according to Reuters.

Florida has 25 cases which account for the majority reported in the United States, according to state health officials and the U.S. Centers for Disease Control and Prevention, Reuters reported. The cases in the continental United States have not been transmitted by local mosquitoes, which would raise the threat.

Along with new reports, the CDC is monitoring chikungunya in Arkansas, California, Connecticut, Maryland, Minnesota, Nevada, New York, Virginia, Puerto Rico and the U.S. Virgin Islands, according to Reuters.