At least 20 New Jersey residents have tested positive for chikungunya, a mosquito-borne virus that has spread through the Caribbean. (July 30)

When the Pennsylvania Department of Health issued its first warning a little more than a month ago about a new virus with a strange name, it may not have seemed like cause for much concern.

The sometimes-disabling virus, called chikungunya (pronounced chik-en-gun-ye), is transmitted via mosquito bite, but only three people in Pennsylvania had it, and all of them had gotten bitten during overseas travels.

Public health experts, however, knew that with the vector — or means of transmission — present in Pennsylvania, chikungunya eventually would make its presence known in a bigger way.

"If you have the vector, you'll have the disease," said Dr. Jeffrey Jahre, section chief of infectious diseases at St. Luke's University Health Network.

And indeed, in only a month, the virus has started to take off in Pennsylvania. The state last week reported 12 confirmed cases, but the actual number likely is higher. St. Luke's has treated two patients with it, and Lehigh Valley Health Network last week had four confirmed and four suspected cases.

Chikungunya also is landing at an inopportune time. The state has cut spending on its mosquito eradication program, and hasn't sprayed in public areas in the Lehigh Valley at all this year. While that indicates another mosquito-borne disease, West Nile virus, is at a low level now, it does leave the door open to the new virus.

At least it's new here.

Chikungunya was first described in 1952 in Tanzania, according to the World Health Organization. It is a term in the Kimakonde language roughly translated as "to become contorted," which describes the posture of those afflicted with the virus from the joint pain they feel.

Symptoms usually develop three to seven days after the person is bitten. While chikungunya is not a fatal disease, it often results in fever, rash, muscle aches and joint pain. The pain can be disabling, and it can last for years, according to WHO.

There is no vaccine to prevent chikungunya, nor is there a treatment for it, so doctors can only recommend rest, fluids and over-the-counter medicine to treat the pain and fever.

The virus is carried by two types of mosquitoes: Aedes aegypti and Aedes albopictus. Both species are found in the southeastern United States and some parts of the Southwest. But Aedes albopictus also is found in the mid-Atlantic states, including Pennsylvania.

Chikungunya was endemic largely to Africa and Southeast Asia, until it jumped the ocean to the Caribbean islands. It was discovered on the island of St. Maarten late last year. Public health officials found that the cases soon were locally transmitted — when a mosquito bites someone who is infected with the virus and then bites another person.

In no time, the virus exploded across the islands, including Puerto Rico. Residents who had been bitten and suffered nothing more than a welt and an itch now were finding themselves feverish and, in some cases, in great pain.

That's when public health authorities started counting the days until chikungunya showed up here.

"We also knew when it occurred that way in the Caribbean that it would only be a matter of time … before there were locally transmitted cases in the United States," Jahre said.

In a matter of months, nearly 500 people across the United States have confirmed travel-related cases of the illness, according to the U.S. Centers for Disease Control and Prevention. However, four cases in Florida have been confirmed in people who did not travel to areas where chikungunya is endemic.

The big question for the rest of the country is how far chikungunya will spread via local transmission.

"Who's to say?" Jahre said.

In a briefing July 17, the CDC said it thinks chikungunya will behave like dengue virus in the United States, where imported cases have resulted in sporadic local transmissions but have not caused widespread outbreaks. It said that none of the more than 200 imported chikungunya cases between 2006 and 2013 triggered a local outbreak, but as more infected travelers return to areas where the virus is not local, the likelihood of local transmission grows.

Public health officials have relatively recent experience with the West Nile virus that teaches them to be wary about predicting the next steps.