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African Viral Disease Spreads

The Asian tiger mosquito, an invasive, disease-carrying pest, may spread to new areas as a result of global warming. The mosquito breeds faster in warmer temperatures. It's a known carrier of the Chikungunya virus. (AP Photo/Jim Newman, University of Flo
It’s not an illness you hear much about, but it can make a person feel miserable for years. And it’s sometimes fatal. It’s spreading and scientists describe the mosquito-borne disease as a major public health threat around the world.

It’s called Chikungunya. The World Health Organization says the name comes from the Kimakonde language spoken along the Mozambique-Tanzania border. It means “to become contorted.” The name describes those suffering from the disease because they are often stooped over.

Dr. Scott Weaver, director of the Institute for Human Infections and Immunity at the University of Texas Medical Branch, said, “It’s a mosquito-borne virus. It originated in Africa and still circulates there now. Its original transmission cycle involves mosquitos in forest habitats and non-human primates. That’s the main vertebrae hosts. But periodically it emerges from that cycle into an urban cycle involving people and different kinds of mosquitos.”

The most recent emergence from the African cycle, he said, occurred in 2004.

“It’s not normally life threatening. There are a few fatal cases. The case fatality rates recently have been estimated at about one in 1,000 people. But even though it’s not normally fatal, it’s a very painful and debilitating disease that can incapacitate people for weeks to months or even pain can persist for years.”

And it can be mistaken for other illnesses.

“It starts off like many other flu-like infectious diseases with abrupt onset of fever and headache and body aches. But what distinguishes it from most others is that the pain is focused on the small joints like the hands, the wrists and the ankles. And that’s accompanied by swelling. And the combination of swelling and pain can leave people pretty severely incapacitated,” said Weaver.

He said that Chikungunya is currently circulating in India and many areas of Southeast Asia. But a lack of accurate diagnoses means it’s unclear just how many people there are infected. Cases were reported in northern Italy in 2007 and in southern France in 2010. Late last year, cases were reported in the Caribbean and two countries in South America.

Weaver does not think it will stop there.

“I think that we will see some cases in the southern U.S. We can predict, I think fairly well, what will happen with Chikungunya because it’s a very similar disease and transmission cycle to Dengue virus and we have a lot of experience with Dengue. Typically, with dengue, we see cases along the Mexico border and south Texas. And then we see outbreaks of focal transmission from imported, infected travelers in Florida,” he said.

There are two different strains of Chikungunya. The strain from eastern Africa in 2004 is able to easily mutate and increase its ability to infect the Asian tiger mosquito. The bloodsucker is found on every continent except Antarctica.

Another African strain that emerged in the 1950s is much less able to adapt and infect the Asian tiger mosquito. It’s the one found in the Caribbean. Its inability to adapt could limit its spread. Right now, Its primary vector is the so-called yellow fever mosquito.

Climate change and means of transport, like ships, can help spread the disease-carrying mosquitos.

There’s no treatment available, just drugs to try to ease the symptoms. However, vaccine research is underway and human clinical trials are about to begin. One of the vaccine candidates was developed at the University of Texas Medical Branch. An effective vaccine against Chikungunya is still years away.