BANGKOK, Aug. 30 (Xinhua) -- Thai authority is on vigilant for the possibility of an outbreak of bird flu after patients contracting the disease were reported in neighboring countries, MCOT reported on Tuesday.

Pasakorn Akarasewi, director of Thailand's Bureau of Epidemiology said that the United Nations warned of a possible resurgence of the bird flu outbreak, calling for all countries to heighten surveillance.

There have been no H5N1 patients so far and no suspicious deaths of poultry, he said.

However, patients contracting the disease were recently reported in Vietnam and Cambodia.

Regarding drug resistance problems, he said no irregularity was detected in the use of influenza drug Tamiflu.

Government Pharmaceutical Organization (GPO) head said there have been no reports of H5N1 avian influenza virus showing resistance to Tamiflu.

More than 20 million doses of Tamiflu produced in 2009 are in Thailand's stockpile, and the drug expires seven years after its manufacturing date.

The GPO started testing live, attenuated influenza vaccine from H5N3 virus. If succeeded, it can be used to prevent the infection.

The United Nations Food and Agriculture Organization (FAO) said migrating birds caused the H5N1 to spread to many countries, but no outbreak has been reported for several years in Israel, Palestine, Bulgaria, Romania, Nepal and Mongolia. Since the virus emerged in 2003, it has claimed 331 lives and infected 565 people.