HANOI, Vietnam - When Nguyen Thanh Hung first heard he had bird flu, he knew he had to stay awake despite a crushing headache and raging fever that fueled his unquenchable thirst. Days earlier, he'd watched his older brother battle the same symptoms, fade into a coma and die.

On Jan. 11, the day of his brother's funeral in their home province of Thai Binh, about 60 miles outside the capital of Hanoi, Hung, 42, developed a mild fever and sought treatment two days later.

As his condition worsened, the doctors confirmed that both Hung and his 47-year-old brother had been infected with the H5N1 strain of bird flu that has killed nine people in Vietnam since Dec. 30 in a new resurgence.

Last year, the avian influenza virus spread to 10 Asian countries, killing or forcing the slaughter of more than 100 million birds. A total of 41 people in Vietnam and Thailand have died of it since the outbreak began. There's no vaccine or treatment, and about 70 percent of those infected have died.

With odds like those, Hung knew he must fight.

"I felt like my head was pressured by a vise and it was breaking into pieces," he told The Associated Press on Wednesday while sitting on his hospital bed in a quarantined room. "I told myself that I had to be alert and not be in the condition of my brother. I thought that if I went to sleep, I could go into a coma."

For three long days Hung's fever burned, peaking at 105.8 degrees and never dropping below 102.2. His legs and arms ached, and pains shot through his joints and muscles. His heartbeat raced and his vision was blurred, causing the room to zoom in and out around him.

All the while, health experts tried to piece together how Hung and his brother were infected.

At first they feared the virus had passed from one brother to another, raising larger questions about how the disease is being spread. So far, most human bird flu infections have been traced to sick poultry, but the World Health Organization believes isolated cases of human-to-human transmission have occurred in the past.

An investigation into the brothers' illness is still going on and the mode of transmission has not been firmly established, said Peter Horby, a WHO epidemiologist in Hanoi.

Hung said the family gathered for a meal on Dec. 25 after the death of his older brother's 2-year-old child. The brothers ate raw duck blood pudding, a delicacy, and drank rice wine as they always did during family reunions.

A third brother who also ate the blood pudding reportedly tested positive for the virus, but WHO has not confirmed that case and Horby said the test results are still being analyzed. The third brother is healthy and has not developed bird flu symptoms.

Vietnam has said it's bracing for the virus to spread more rapidly when the Lunar New Year, or Tet, festivities begin next month. Most Vietnamese travel to be with their families during the holiday, and the traditional offering made to ancestors during that festival - even in the poorest households - is a chicken.

But as the Year of the Chicken approaches on Feb. 9, Hung said he and his wife are looking forward to a quiet Tet holiday in Hanoi without any poultry on their dinner table. He has fully recovered and is expected to be discharged from the hospital this week - the only confirmed bird flu case this year to survive.