>>The Public Health Ministry has issued an alert about the return of Chikungunya disease, which has spread to 23 provinces and affected more than 20,000 people since January.

The southern provinces are hardest hit with almost 8,000 cases reported in Songkhla province alone.

The announcement, released yesterday, said health authorities will intensify their war on garden-striped mosquitoes, which spread the disease, after 20,541 cases were recorded in 23 provinces from the start of this year to May 20.

The number of people taken ill, which has increased by more than 5,000 people in less than a month, has persuaded provincial public health officials to step up their mosquito eradication campaign, particularly in the South, where dark and humid rubber plantations make ideal mosquito breeding grounds.

The southern provinces of Nakhon Si Thammarat, Narathiwat, Pattani, Songkhla, Trang and Yala have reported unusually high numbers of people infected with Chikungunya disease since January.

Pattira Thangrattanasuwan, director of the Crown Prince Hospital in Pattani's Sai Buri district, said the vector-borne disease had now become the most serious health threat to people in the deep South.

"The hospital has made Chikungunya the number one health threat, ahead even of the southern violence which had been ranked the top cause of physical and mental illness among Sai Buri people," said Dr Pattira.

More than 800 people had come down with the disease in the district over the past six months, she said.

The re-emergence of the disease in rural areas after a long period of absence in 1995 prompted health authorities to question whether Chikungunya disease had developed into a more dangerous strain. Vichai Satimai, director of the vector-borne disease bureau, said the current Chikungunya outbreak was related to the African strain of virus, which could spread rapidly.

A specific study on changes in virus virulence had not yet been made.

However, an expert in vector-borne diseases believed climate change might affect the life cycle of mosquitoes, enabling them to produce a minimum infective dose of the dengue or Chikungunya viruses faster than before.

"Chikungunya fever is not life threatening. But patients may experience persistent joint and muscle pain up to a year or more which obviously can affect their way of life," he said.

Symptoms of Chikungunya fever occur among adults more than children, unlike dengue fever. Pain medication and long-term anti-inflammatory therapy might be required, he said.

Paijit Warachit, Public Health Ministry deputy permanent secretary, said health agencies were trying to contain the disease by sending provincial staff and health volunteers to spray rubber plantations with chemicals that kill mosquitoes and larvae in water sources.

Residents would be told to destroy breeding grounds of the disease carrier and protect themselves from mosquitoes by using mosquito nets and repellent lotion.

Dr Paijit said the opportunity for Chikungunya flare-ups in other areas apart from the South was slim due to geographical differences.

However, reports of isolated cases in different parts of the country were possible and national surveillance was needed among targeted police, military and students returning home from the South to ensure that the outbreak was contained.

Meanwhile, thirteen cases of Chikungunya disease have also been reported in the northeastern province of Ubon Ratchathani. These people developed the disease after returning from working at a rubber plantation in the South, said Sarayut Uttamangkapong, director of the disease control and prevention northeastern office.