Asian tiger mosquitoes are abundant in the U.S. and can spread chikungunya, a viral disease that causes high fever, arthritis and eye inflammation, and up to now is unknown here.

Dr. James Diaz, program director of Environmental/Occupational Health Sciences at Louisiana State University Health Sciences Center, said he fears that because we have mosquitoes that can transfer this virus, it’s only a matter of time until the U.S. faces chikungunya, an illness formerly confined to the Eastern hemisphere. Currently, there is no vaccine for the virus.

Diaz said the Asian tiger mosquito is “in your backyard along Michigan Avenue,” so the exotic chikungunya virus, which is normally seen near the Indian Ocean could easily cause a local epidemic in the U.S.

A July 2009 article in Emerging Infectious Diseases reported that many people with chikungunya around the Indian Ocean are also infected with dengue, a fever that causes severe headaches and muscle and joint pain.

The article reported that Asian tiger mosquitoes also carry dengue. Dengue virus is already present in the U.S., and again, there is no vaccine.

“We have a setup that we could potentially have both chikungunya and dengue circulating in mosquitoes,” Diaz said. “Co-infections of viruses we don’t have vaccines for make us very concerned.”

In the past, mosquitoes were in the spotlight because of the role they play in spreading West Nile virus. Diaz said 9 out of 10 people infected with chikungunya experience symptoms, whereas 9 out of 10 people infected with West Nile are asymptomatic.

Roger Nasci, chief of the Arboviral Diseases Branch at the Centers for Disease Control and Prevention, said that while more people get sick from it, “the fatality rate for serious chikungunya is very, very low compared to West Nile virus, where the fatality rates are as high as 10 percent.”

Nasci said he believes “the public health infrastructure in the United States is aware of the potential for chikungunya and has taken appropriate steps for preparation.” He said the CDC has trained doctors in states around the country to respond, diagnose and treat infected people quickly.

Mark Dworkin, an associate professor of epidemiology at University of Illinois at Chicago said, “I can see why a development of a vaccine would be useful for places in the population where [chikungunya] is endemic, or for travelers who are heading to an endemic region,” but noted it should not be a priority for the U.S. because we have not had an outbreak.

Diaz said that the U.S. has not heeded warnings from Italy and France in the last two years to prepare for the virus. Both countries faced local outbreaks of chikungunya, which was brought back by travelers who visited the Indian Ocean region.

“The scenario [in the U.S.] would be similar to what happened in Italy in 2007,” Nasci said. “An infected traveler comes back carrying the virus [and] gets bitten by local mosquitoes that are competent to transmit the virus. They then incubate the virus and transmit it to somebody else.”

Still, Dworkin said time is on our side because mosquitoes can only obtain the virus from someone’s blood in the first three to four days of illness. That is “a relatively short period of time that somebody would have the virus that a mosquito can get a hold of,” he said.

Also, Nasci said the presence of window screens and air conditioning lessens America’s exposure to diseases spread by mosquitoes, unlike the high exposure in developing countries where these diseases are rampant.

Dworkin said the name chikungunya comes from a native Tanzanian language and means “that which contorts or bends up,” which probably refers to the arthritic effects of the virus.

Although chikungunya may not strike as severely in the U.S. as it does in the Eastern hemisphere, Diaz said he is afraid this virus and its ability to co-infect with dengue will not be publicized because the West Nile threat on the U.S. did not leave a lasting impression and the country is currently focused on swine flu.

tgleason@chroniclemail.com