"Please don't rush to seek vaccinations against human influenza. Healthy people don't need vaccines, which should only be used for people in risk groups such as health professionals who have to take close care of patients, disease-control officials or livestock officials," said Dr Kamnuan Ungchusak, who heads the Public Health Ministry's Bureau of Epidemiology.

Ministry spokesman Dr Suphan Srithamma said the three patients who succumbed to influenza this year were a 41-year-old man, a five-year-old girl and a two-year-old girl.

Suphan said children, the elderly and ailing people would be among the risk groups when it came to the human-flu threat.

Medical Sciences Department director general Dr Paijit Warachit said that although primary checks had showed human influenza was spreading in some provinces and had not mutated into another strain of human flu, a detailed lab test was continuing.

The Bureau of Epidemiology said human influenza was now spreading in Bangkok, Nong Khai, Angthong and Prachuap Kiri Khan. About 160 people have caught the flu this month.

Last year, 16,309 people came down with influenza. Two of them died.

Meanwhile, agencies are stepping up measures against bird flu.

In Tak, the provincial public health office covered its compound with nets to prevent wild birds from getting in. Security guards also made banging sounds to scare the birds away.

"These measures help reduce bird-flu risks. Besides, they make the compound clean and easier to maintain," said Tak public health office chief Dr Pajjuban Hemhongsa.

In Uttaradit, provincial livestock chief Panom Meesiriphan said his authority was closely monitoring more than one million chickens and ducks in Muang, Laplae, Phichai and Tron districts where bird-flu infections were detected last year.

"So far, we haven't detected any bird-flu infection in our province this year," he said.