As a growing number of cases of the unpleasant, mosquito-borne chikungunya virus crops up across the country, the Pennsylvania Department of Health on Thursday issued an alert about the illness, which until very recently has had little presence in the U.S.
Chikungunya, a nonfatal virus that causes fever and joint pain, has crept onto American soil in unusually high numbers this summer. From 2006 to 2013, studies found an average of 28 cases per year in the U.S. — all associated with foreign travel, mostly to Asia. As of Tuesday, 129 cases already had been reported this year in the U.S. and its territories, according to the U.S. Centers for Disease Control and Prevention.
All of the cases reported in the contiguous U.S. were travel-associated, mostly with the Caribbean, which saw its first locally transmitted cases of the virus last year.
This means that none of the reported cases was transmitted within the U.S., but American doctors are seeing the virus when travelers visit or return from the Caribbean and show symptoms here. Some cases were reported in Puerto Rico.
Three of this year’s cases were reported in Pennsylvania; only two cases were reported in the state in the previous 10 years, according to Holli Senior, Pennsylvania Department of Health spokeswoman.
The health alert aims to build “awareness for our physicians out there that it’s there,” said Ram Nambiar, the director of infectious disease epidemiology for the Pennsylvania Department of Health.
“We want people to be aware of that and make sure that they properly follow through with patients,” Mr. Nambiar said.
As health departments begin to place more focus on the virus, they also have started to pay attention to the mosquitoes that can spread it.
One mosquito known to carry chikungunya is tropical, but a second type — the day-biting Asian Tiger mosquito, which can be identified by its black and white striped body — is common in Pennsylvania.
Last year, the Pennsylvania Department of Environmental Protection directed a pilot surveillance and control program for the mosquito in Hanover and this year moved the pilot to York, according to spokeswoman Amanda Witman.
In Pittsburgh, the mosquito has become more common in Lawrenceville and Bloomfield the past five years, according to Bill Todaro, an entomologist with the Allegheny County Health Department.
The county health department surveyed for Asian Tigers in some areas last year when it received “decent” numbers of complaints about them and is repeating the practice this summer, he said.
The Asian Tiger is one of three mosquitoes that the county health department is targeting in Pittsburgh, although officials are not yet spraying for it specifically.
The department’s priority remains mosquitoes that carry West Nile Virus, Mr. Todaro said.
With Asian Tiger mosquitoes “all over Pennsylvania,” the health department knows the possibility exists for locally transmitted cases of chikungunya to crop up in the state, Mr. Nambiar said.
“It’s here now,” he said. “It’s just getting folks aware and making sure that they use proper preventive techniques.”
Madeline R. Conway: firstname.lastname@example.org, 412-263-1714 or on Twitter @MadelineRConway.