COLOMBO (Reuters) — Sri Lanka has confirmed an epidemic of the mosquito-borne Chikungunya viral fever, a top health official said on Saturday. Doctors suspect it has infected 5,000 people in the island's far north.Dr. Nihal Abeysinghe, director of the state Epidemiology Department, said pockets of the fever had been detected in Sri Lanka's northwest, south and east, but could not say how many cases had been reported.

"We have got some samples down to Colombo and we handed them over to five different laboratories. All five have reported it as Chikungunya," Abeysinghe said. "You could say it is (an epidemic)."

"We have confirmed there is an outbreak going on in Kalmunai, Mannar, Batticaloa, Puttalam and some parts of Colombo city," he added. "It is in densely populated pockets."

Abeysinghe said he believed up to 60 percent of reported fever cases were due to Chikungunya.

"There are several different fevers. Not all fevers reported are Chikungunya," he said, but added that bird flu was "very, very unlikely because there are no respiratory symptoms, no cough or cold or anything like that".

However laboratories had yet to confirm whether an outbreak of viral fever in the northern Jaffna peninsula, cut off from the rest of the country for months amid renewed civil war between the state and Tamil Tiger rebels, was Chikungunya as suspected.

The outbreak comes as Sri Lanka also grapples with a sharp increase in dengue fever cases as monsoon rains create breeding conditions for mosquitoes which carry the diseases.

Symptoms of Chikungunya include high fever, joint and muscular pain, severe headaches, body aches and a rash similar to that seen in dengue patients. While the disease is painful, the US Centers for Disease Control and Prevention (CDC) says no deaths from Chikungunya have been documented in scientific literature.

Dr. A. Ketheeswaran, director of provincial health services for the Jaffna peninsula, suspects the viral fever spreading in the far north is Chikungunya.

"In Jaffna, this viral fever which has the symptoms of Chikungunya is spreading very fast. I find that more than 5,000 people have been infected," Ketheeswaran said.

Cut off behind rebel lines, Jaffna residents are living on rations shipped in by sea from the south, and medicines and food are in short supply. Residents said doctors had recommended paracetamol as a fever preventive, but most shops had run out.

Abeysinghe said it was very unlikely that Chikungunya caused the death on the peninsula of a Tamil woman suffering from viral fever on Friday.

"It is very unlikely to be (due to Chikungunya). There may be a lot of other disease conditions associated with these people who are reported to have died due to Chikungunya," he said.

Chikungunya, Swahili for "that which bends up", was first isolated in the blood of a febrile patient in Tanzania in 1953, the CDC said.