The first cases of locally acquired chikungunya fever have occurred in Miami-Dade and Palm Beach counties, making it the first time the severely painful virus has been spread by a mosquito in the United States, Florida health officials said Thursday.

Health department officials said they believe persons in both cases were bitten by an infected mosquito in South Florida that had bitten someone who had acquired the disease in another country.

A 41-year-old Miami-Dade woman first started experiencing some of the symptoms of the mosquito-borne illness on June 10. She developed a fever and health officials confirmed her case. A 50-year-old Palm Beach County man was also confirmed. He first complained of symptoms July 1.

Officials said the two had not traveled out of the country before being infected.

The disease is rarely fatal, although its symptoms include fever, severe joint pain, or swelling or rashes. The arthritis-like symptoms can last for years.

Walter Tabachnick, director of the University of Florida’s Florida Medical Entomology Laboratory in Vero Beach, said no one should be surprised by the confirmations.

“We expected this. Now the question is what are the cases to follow and can Mosquito Control itself do something to mitigate what ever those numbers might be?” he said. “It’s not clear yet, how many more cases are there to follow in addition to these initial cases.”

County officials said they are looking to increase the spraying.

“We’re trying to put in our plan on how to be a little more proactive with our spraying,” said Manuel Garcia, Miami-Dade County’s Road, Bridge, Canal and Mosquito Control Division chief. “We don’t want to set a concrete plan; we have to come up with an adjustable plan based on the mosquitoes, and adjust the plan routinely.”

Garcia said when the health department notifies his division of a suspected or confirmed case, they spray in a square-mile area where the case was reported for about two weeks. Garcia said his division will collect data and look at the movement of the mosquitoes throughout the county.

Tabachnick recently led a two-day seminar on preventing the spread of chikungunya and dengue fever for public health and mosquito control personnel. He said no one can be certain that the virus-carrying mosquitoes haven’t been in Florida until now.

“Are these indeed the first cases? There are probably other people who got sick from an infected mosquito and didn’t report it,” Tabachnick said. “The issue is whether they are now going to start showing up in doctors’ offices.

“Within the next months, we will know whether or not we are out of the woods.”

Beyond spraying, officials are calling on residents to drain any standing water around them, to cover up when they go outside and to cover their doors and windows with screens. Reynald Jean, the manager of the county health department’s tuberculosis prevention program, said it’s especially important because the aedes aegypti and aedes albopictus mainly bite during the day.

“They’re daytime mosquitoes, so they’ll bite early in the morning or in the late afternoon,” Jean said.

He also suggested that if a person experiences symptoms they should visit their physician as soon as possible. They should not take aspirin because the symptoms are similar to dengue fever, which does not react well to aspirin. Tylenol is recommended. Symptoms normally develop three to seven days after a person has been bitten, according to the Centers for Disease Control and Prevention.

Though it has been around since the 1950s, chikungunya (\chik-en-gun-ye) fever was first detected in the Western Hemisphere in December when it was detected on the French island of St. Martin. As of July 11, the Pan American Health Organization said there were 5,037 confirmed cases and 350,580 suspected cases of chikungunya in 23 countries and territories, including El Salvador in Central America; Suriname and Guyana in South America; and the U.S. territory of Puerto Rico.

On Thursday, Puerto Rican health officials declared the disease an epidemic after confirming more than 200 cases, mainly in San Juan and surrounding areas.

In Haiti, where the virus has spread with a vengeance, residents say it seems to have slowed down with fewer reports of people showing an acute fever and severe joint pains. There is still no vaccine or medicine to treat the disease, but most patients recover within a week, according to the CDC.

The woman infected in Miami-Dade is said to have “recovered” and is “doing fine,” said Jean, of the county health department.

Officials continue to stress that the disease cannot be transferred from one person to another and is typically not life-threatening, but that should not deter people from taking preventative measures.

“There are places that may produce mosquitoes and these property owners have to clean these places up,” Tabachnick said. “The neighborhood has to demand they clean it up. No one has the right to reproduce mosquitoes and endanger your health.”