Health officials meeting today and tomorrow will work towards greater regional cooperation to fight the disease.

In recent years, dengue epidemics have re-emerged to become a serious global health concern, said the World Health Organisation (WHO)'s regional adviser on vector-borne disease control, Chusak Prasittisuk.

The emergence of dengue epidemics in Asia and the Pacific was of particular concern, with nine out of 11 countries in the region currently affected by the disease, he said.

Of greatest concern is dengue's apparent unrelenting march across the Asia-Pacific, with Bangladesh, Bhutan and Queensland in Australia having recently been added to the affected-countries list.

Even in Singapore, where control of dengue has been very effective for more than a decade, epidemics still occur.

The cyclical nature of dengue epidemics is also tightening, with outbreaks every few years now compared with every 10 to 20 years in the past.

"It's been moving from one country to another, in association with migration of the world population," said Chusak.

Every year globally, there are about 50 to 100 million cases of dengue fever and 500,000 cases of dengue haemorrhagic fever, which kills about 25,000 every year, said Chusak.

Dengue epidemics have recently occurred in North America and Europe after a long absence, said Duane J Gubler, director of the Asia-Pacific Institute for Tropical Medicine and Infectious Diseases.

He said the main factor behind the disease's global resurgence was a lack of effective controls.

Rapid and uncontrolled urbanisation and the faster movement of the world population are also to blame for the epidemic's spread, plus climate change that has improved conditions for the disease carrier, the domestic Aedes aegyptii mosquito.

And so health officials representing the major countries of the Asia-Pacific have come together in Chiang Mai to try and improve regional cooperation in fighting the disease.

The meeting is expected to agree on a regional partnership to fight dengue, said Dr Kevin Palmer, a vector-borne disease expert with the WHO's Western Pacific region.

The expected regional cooperation will be aimed at increasing the capacity of member countries when it comes to surveillance of the disease, creating a transparent information-sharing system, strengthening dengue case management and national plans to tackle not only epidemics, but also isolated outbreaks.

"Most of the time, we don't know about dengue outbreaks until they've been reported in the newspapers," said Palmer, adding that this showed a lack of effective surveillance and an information-sharing system.

Many countries [affected] rely largely on tourism [for foreign earnings] and since reports of dengue epidemics could impact on their economies, some of them simply cover up information, he said.

Political commitment is also crucial, said Gubler.

"We have global funds for HIV, tuberculosis and malaria, but we don't have such a thing for dengue," said Palmer.

"This disease is serious, but not severe, and that's why it's very difficult to convince countries to invest in fighting dengue," said Dr Narongsakdi Aungasuvapala, Public Health Ministry deputy permanent secretary.

With no vaccine on the horizon for at least seven years, the best course to prevent dengue is stabilising control of the disease carrier - mosquitoes.

"You've got to remember the key to controlling this disease is prevention," said Gubler.

"We can't just wait for the vaccine."

Arthit Khwankhom

The Nation