The Hanoi Hilton’s club sandwich no longer features chicken.

The chief bird flu fighter in the northern Thai Binh province, where a cluster of human cases has caused concern, is trying to stop chickens from crossing the road to reach - and infect - the other side.

A survivor in the province swears never again to eat fowl.

But a longtime chicken seller can’t understand what the fuss is all about and the elder sister of another survivor ate chicken in Hanoi while her brother struggled for life on a respirator.

There are as many bird flu voices in Vietnam at the moment as the cackling and crowing of the millions of fowl - chickens, ducks, geese, quail - that dot the land and rice paddy fields.

After 15 deaths in Vietnam since December 2004 out of 41 patients stricken in that period by the H5N1 bird flu virus, chicken is mainly off the menu and under the microscope.

Since the disease first hit Asia in late 2003, killing since then a total of 36 Vietnamese, the communist nation has reported a total of 68 human infections among a population of 82 million.

In the same time, 12 Thais and four Cambodians have also died of the virus including a 20-year-old Cambodian woman who was a rushed to a hospital in Vietnam last week.

The World Health Organisation (WHO) says the virus could mutate into a form that could pass easily between humans and cause a worldwide pandemic in which millions could die.

THE DOCTORS

Doctor Pham Van Diu, director of the Centre of Preventive Medicine in Thai Binh, 110 km (68 miles) south-east of Hanoi and the site of three bird flu “cluster” outbreaks this year, is in the front line of the battle.

Diu, who has worked in the Red River Delta province since 1984, seeing it safely through such scourges as bubonic plague, cholera, polio and dengue fever, admits he is perplexed.

“It is a big jigsaw puzzle and there is not just one piece missing but many pieces missing,” he says.

Why do people who slaughter chickens, and would seem most at risk, seem immune? Why does the flu seem to strike mainly within families? Why have there been no foreigners among the stricken?

“When it first appeared we thought it was SARS,” he said. “But it didn’t follow rules of past diseases like many victims, more dead, as well as less time and space between outbreaks.”

He says strict measures to control movement of poultry, isolation of cases and public awareness allowing early diagnosis have helped Vietnam control the spread for the moment.

Diu said last year 1.5 million birds were slaughtered in a cull of the sick. In the first three months of this year, only 15,000 have been slaughtered.

Peter Horby, a medical epidemiologist with the WHO in Hanoi, gives Vietnamese authorities high marks for most measures they have taken.

But he warns: “We need to resolve the mystery of bird flu, not just contain it and learn to live with it.”

He said the number of outbreaks dotted around Vietnam shows bird flu is still “entrenched” in various parts of the country.

Horby fears the day when 20 people come down with bird flu on the same day and in several different locations.

“But we are not there yet,” he says.

THE SELLERS

Ha, a 50 year-old seller of live chickens in a Thai Binh city market, scoffs at a bird flu threat.

“If there is a threat, why haven’t any people like me been sick,” she asks, thrusting her face into the wire mesh of a cage containing 20 live roosters.

Like other people in the market, Ha only gave her first name saying she had sold chicken for 15 years, carrying on a livelihood started by her parents who also had never been ill.

“If you don’t eat sick chicken and if you cook the chicken well, there is nothing to fear,” she says.

At another stall, Huyen, who sells slaughtered chickens, says her daily sales this year are less than half the 50 she used to sell.

“If you only sell healthy chicken, you never die,” she says, while admitting that she now buys her birds also from other provinces, rather than just Thai Binh.

But Yen, an 80-year-old woman who sells joss sticks and other non-food items, disagrees.

Wagging a stern finger she warns: “If you eat chicken, you die. Here. Now.”

THE SURVIVORS

Nguyen Thi Ngoan, 14, is back at school this month, a survivor, like her 21-year-old brother and 81-year-old grandfather, of bird flu.

The family lives in Thai Binh province’s Ho Doi 2 hamlet, about an hour’s drive from the provincial capital.

She spent nearly three weeks in hospital, catching the flu several days after her brother was stricken in January. The pair, along with their grandfather, had eaten chicken together.

The grandfather was diagnosed with the flu but never showed its outward symptoms of fever and a shivery cold.

“I will never eat chicken again,” Ngoan says. “Once near death is enough. I also don’t like some mean schoolmates calling me bird flu girl.”

Just last week her 21-year-old brother came off a respirator and is on the way to a full recovery.

“He never believed he had bird flu,” says elder sister Nhung who cared for him while he was in hospital in Hanoi.

“The day he fell ill he got wet and thought it was just a bad cold.”

Nhung admits that while looking after him in Hanoi she ate chicken but she would never eat it again in her own province.

“When our brother comes home we will have feast - my mother’ll kill a cow, not chicken,” says the younger sister Ngoan.