The bacteria enter the body when bruised skin comes into direct contact with contaminated soil or water, leading to abscesses and blood poisoning. Victims experience fever, coughing and shortness of breath. In some cases they develop pneumonia.

The death rate hit 40 percent between January and July this year, up from 10 percent last year, the ministry said. Up to early September, 79 people have been diagnosed with the disease.

That death rate was three times that of Severe Acute Respiratory Syndrome (SARS), which killed 13 percent of sufferers, K. Satkunanantham, the ministry's director of medical services, told a medical conference.

The high number of fatalities had led the ministry to investigate whether the disease was being caused intentionally, as the bacteria are a potential biological weapon, Satkunanantham said. It found no sign that the bacteria had been manufactured.

Satkunanantham said that more than 80 percent of the victims who died had pre-existing health problems, such as diabetes, hypertension and kidney failure.

There is no vaccine for melioidosis but the illness can be treated with antibiotics if detected early. Diagnosis requires testing of a saliva sample.

Melioidosis is common in Southeast Asia, with cases concentrated in the area from Vietnam to Myanmar and Malaysia, the U.S. government's Centers for Disease Control and Prevention (CDC) says on its Web site (www.cdc.gov). It is also endemic in northern Australia.

The CDC says sheep, goats, horses, pigs, cattle, dogs and cats can also catch the bacteria and spread a similar disease to humans.