An outbreak of mosquito-borne virus Chikungunya in Papua New Guinea is continuing to spread around the country.
The virus was first detected in Sandaun province last June and has now been reported in Madang, West New Britain, East New Britain, Morobe and Eastern Highlands.
Dr Paul Horwood from Papua New Guinea's Institute of Medical Research is helping track the disease and has told Radio Australia's Pacific Beat there are also suspected outbreaks in New Ireland and Oro provinces.
"It certainly is a concern to the medical authorities in the country," he said.
"We'd have to say there have been tens of thousands of cases around the country."
Dr Horwood says the dengue-like illness exhibits symptoms including a high fever and "quite debilitating" arthritis pain, usually in the arms, legs and shoulders, which can be ongoing.
He says people with the illness can also present with headaches, rashes on the arms, legs, stomach and chest areas, along with abdominal symptoms.
Dr Horwood says the mosquitoes spreading Chikungunya are the "day-biting" kind, also known to transmit dengue fever.
There is no treatment to cure the virus but Dr Horwood says people can avoid exposure by reducing mosquito breeding areas around the house and wearing long clothing and mosquito repellent.
Papua New Guinea's government has been working with the National Department of Health and provincial health authorities to help distribute information and clean up potential breeding areas.
Dr Horwood says there have been no reported deaths from Chikungunya in the country.
"Luckily death from Chikungunya is quite rare," he said.