'It is likely that dengue fever will be more severe this year than last year,' said Mr Thawat Suntrajarn, director-general of the disease control department at the public health ministry.

The disease has already killed six and sickened more than 5,800 since the beginning of this year, Mr Thawat said, warning that the number of new infections could surge during Thailand's rainy seasons from June to August.

Thailand has suffered 1,000 more cases than during the same period of last year, he said.

In 2007, dengue fever killed 91 people and infected more than 63,000 in Thailand, according to official data.

Dengue is usually associated with poorer tropical countries. The disease leads to a sudden onset of fever with severe headaches, muscle and joint pains, and rashes. -- AFP