The World Health Organization reports there have been almost two million cases of the mosquito-borne illness, Chikungunya, throughout parts of Asia since 2005. Researchers are testing an experimental vaccine to prevent outbreaks, which also occur in Africa and the Americas.
The virus is transmitted through infected female mosquitoes that bite during the day. The mosquitos also transmit other viral diseases including Dengue fever.
In fact, the symptoms of chikungunya - including fever, rash, headache and severe joint pain - are often mistaken for dengue, another tropical illness that causes severe aches and pains and a high fever.
Working to develop a vaccine against chikungunya - which the WHO says has reached epidemic proportions - researchers used a virus-like particle, rather than the killed or weakened virus used in traditional vaccines. The experimental drug contained outer surface proteins taken from a West African strain of chikungunya, without the genetic material that causes infection. It stimulated a robust antibody response in the majority of the 25 healthy, young American volunteers in the initial trial. The candidate vaccine was reportedly well-tolerated. Antibody response was seen in even at the lowest doses.
More clinical trials and regulatory approval are needed before the vaccine becomes available.
According to the WHO, more than 1.9 million cases of chikungunya were reported in India, Thailand, Indonesia, and Burma over the past decade. There have also been outbreaks in Democratic Republic of Congo and Gabon, in the island countries of the Indian Ocean and the Caribbean. A number of cases have been reported recently in France, Italy and the U.S.
Ann Powers, with the U.S. Centers for Disease Control and Prevention, says it’s hard to estimate how many people have been infected.
“Because there simply isn’t any treatment available. So, they learn from their friends, their neighbors, their family that, “Oh, I’ve got chikungunya. It’s going to be a self-limiting disease. I’ll feel bad for a while, then I’ll recover," said Powers.
But even after they have recovered from the initial infection, people will sometimes feel bad for months and even years with severely aching joints.
Looking ahead to the possible release of an approved vaccine, Powers says in the United States, it might be given to overseas travelers.
“In contrast, in some place like India where they have chikungunya circulating continuously, it might be something they might want to incorporate into their routine, vaccine regimen," she said.
Until then, Powers say the best protection continues to be avoiding mosquito bites by covering up and using an insect repellant.
An article on human trials of an experimental chikungunya vaccine is published in the journal The Lancet.