HANOI -- Nguyen Sy Tuan can barely talk. His wasted frame is tucked beneath a thin white sheet on the hospital cot. His cheeks are sunken and his bulging eyes stare blankly at the ceiling. But the young man has begun to eat rice again and can finally breathe without a mechanical ventilator, a dramatic turnaround for a bird flu patient whom doctors had assumed would die.
More than a year after avian influenza emerged in East Asia, killing more than two-thirds of the people with confirmed cases, Vietnamese doctors are reporting that the mortality rate in their country has dropped substantially.
Nguyen Sy Tuan lies in bed at Hanoi's Bach Mai Hospital as he recuperates from bird flu. Experts say dropping death rates could signal a wider outbreak.
(Alan Sipress -- The Washington Post)
But while this is good news for survivors, it could mean the outbreak of bird flu in Southeast Asia is taking an ominous turn. If a disease quickly kills almost everyone it infects, it has little chance of spreading very far, according to international health experts. The less lethal bird flu becomes, they say, the more likely it is to develop into the global pandemic they fear, potentially killing tens of millions of people.
"The virus could be adapting to humans," said Peter Horby, an epidemiologist with the World Health Organization in Hanoi, the Vietnamese capital. "There's a number of indications it could be moving toward a more dangerous virus."
The mortality rate for bird flu in Vietnam this year is about 35 percent, almost exactly half that of last year, according to Health Ministry statistics. The mortality rate of the 1918 Spanish flu pandemic, by comparison, was less than 5 percent, but the outbreak killed an estimated 40 million people worldwide.
Officials said the drop in the bird flu mortality rate was more marked in northern Vietnam than in the south. While the virus in southern Vietnam is still killing at the same pace as last year, the rate in the area around Hanoi and elsewhere in the north has dropped from that level to as low as 20 percent. Vietnamese health experts said their suspicion that the disease is shifting is further supported by preliminary research showing a genetic change in the virus in the north resulting in the production of a protein with one less amino acid than in the south.
Health researchers believe that nearly all the 52 people known to have died of bird flu in Southeast Asia caught the virus from infected poultry. But with more clusters of cases among families reported in Vietnam this year -- including that of Tuan, his sister and their grandfather -- experts say they are growing increasingly suspicious that the disease has begun passing from one human to another.
Also worrying is the discovery of at least five cases, including that of Tuan's grandfather, in which people tested positive for bird flu but showed no symptoms. This could make it more difficult to contain an epidemic because people could transmit the disease without anyone realizing it.
Last year, U.S. researchers reported that ducks in Southeast Asia had begun carrying the bird flu virus without showing symptoms. Now, scientists in Vietnam have found numerous asymptomatic cases in the country's vast chicken population, according to Nguyen Tran Hien, director of the National Institute of Hygiene and Epidemiology.
"It seems that the virus may adapt in humans and in poultry a little bit. Therefore, the symptoms are not as severe as before," Hien said. "Also, the transmission may be faster and easier."
Moreover, the existing virus strain is not the only threat. Each human case also presents a chance for the bird flu virus to swap genetic material with an ordinary flu bug -- if the person becomes infected with both strains at the same time -- potentially creating a new hybrid that is highly lethal and even easier to catch.
"We are concerned that if the virus is changing, maybe a new virus is coming in the future," Hien said.
Tuan, 21, left his home among the glistening paddies of northern Vietnam's rice-growing region more than a year ago for Haiphong, on the coast, where he worked harvesting seaweed for use in local cuisine. In early February, he returned to his family's simple brick house to celebrate the Tet New Year holiday.
According to his doctors, Tuan slaughtered a chicken for a festival meal, cutting its neck while his 14-year-old sister clutched the wings and legs. The bird was likely infected, and soon the siblings were, too.