Travellers warned after rare virus surfaces in Canada, U.S.

A handful of people in Canada and the United States have caught a rare but painful mosquito-borne virus while visiting southern India or some Indian Ocean islands near Africa, the top U.S. public health agency says.

The Centers for Disease Control and Prevention delivered the low-key warning on Thursday, saying there has only been a tiny outbreak of chikungunya fever in North America. However, the agency warned that the virushas infected nearly 750,000 people in countriesin and around the Indian Ocean in the past three years.

Chikungunya is similar to dengue fever and causes such severe joint pain that many people adopt contorted postures, but they usually rebound within a week and the disease is almost never fatal, the CDC said.

The agency said 12 cases of chikungunya fever were diagnosed in travellers returning to the United States from abroad between 2004 and 2006 and "additional imported but unrecognized cases likely occurred."

In the 13 years before 2004, there were nine confirmed or probable cases in the United States, the agency said.

In May, Canada reported four confirmed cases among Canadians who had been to the Indian Ocean area, and there have been 340 European cases so far in 2006.

The CDC said that recent outbreaks have taken place in:

• Three states in India (Karnataka, Maharastra, and Andra Pradesh), since April 2006.
• The islands of Mayotte, Mauritius, Réunion (a French territory off the coast of Madagascar) and the Seychelles, in the Indian Ocean off the east coast of Africa near Madagascar, since March 2005.

Chikungunya fever "is characterized by sudden onset of fever, headache, malaise, arthralgias (pain in the joints) or arthritis, myalgias (muscle pain), and low back pain," the CDC said. About half the cases have a skin rash and the pain in the joints can be severe.

While the fever usually lasts less than a week and "full recovery is the usual outcome," some patients have symptoms that can go on for years, the CDC said.

There are no specific drugs or vaccines to treat chikungunya fever.

The CDC advised doctors to be aware of possible infections "in travellers returning from CHIK-fever-endemic or outbreak areas" because there is some risk that the disease could take root in the United States especially in tropical or subtropical areas.

Because the fever is carried by mosquitoes, CDC recommends travellers to affected areas to stay behind screens, wear long-sleeved shirts and pants, and use repellents. If travellers develop the fever, the agency suggests that they stay under a mosquito net or indoors to limit mosquito bites and to avoid spreading the virus to local bugs.