By Tony Cheng
BBC correspondent, Bangkok
Thailand has found cases of bird flu in two provinces, prompting authorities to issue an alert to poultry farmers.
Millions of birds have been culled as a preventative measure
The announcement came as Vietnam said a young woman had died from the H5N1 virus, the sixth death in three weeks.
Both countries are braced for a possible return of the virus that decimated poultry stocks last year, and killed at least 38 humans.
In contrast to the last outbreak, this time the Thai government wasted no time in announcing the new cases.
They were found amongst fighting cocks and poultry birds in two separate provinces, and were the first to be discovered this year.
All infected birds have been culled, and the movement of livestock from both areas has been stopped.
Also on Thursday, Vietnamese health officials announced the death of an 18-year-old, who died after eating chicken infected by bird flu.
Health experts have warned that the cooler winter conditions are allowing latent reserves of the virus to spread amongst poultry stocks with weakened resistance.
The World Health Organisation has expressed fears in the past that bird flu could be the cause of the next global flu pandemic.
That would require a mutation to create a strain of the virus that can be easily transmitted from human to human.
These latest reports show no evidence of that, but the reappearance of bird flu will strike dread into the hearts of poultry producers, who have barely recovered from last year's outbreak.