Two died in hospitals and two others died at home in central Viet Nam.

A source from the National Hospital of Tropical Diseases in Hanoi said they received 16 people infected with the Streptococcus suis bacteria, a pork-based pathogen, since the beginning of this year, including nine during the ten days of the festival that began on 10 February.

The patients were from Hanoi and the nearby provinces of Nam Dinh, Ninh Binh and Thai Binh, and had direct contact with pork through butchering, selling pork, or eating "tiet canh," a type of pudding made with raw pig’s blood.

Two men from Nam Dinh died of severe blood poisoning, two others are also struggling with it, while the rest have developed meningitis, the source said.

Dr Nguyen Trung Cap from the hospital’s Emergency Department said the dead patients were brought to the hospital after having the blood dish, and the condition of both became critical quickly with declining liver, kidney and lung functions.

"Half the patients said they ate 'tiet canh,'" Dr Cap said.

The bacteria also killed two butchers in the central province of Quang Nam during the holiday, Tien Phong reported on 22 February.

Pham Thi Nguyet, 45, died on 8 February, four days after she slaughtered five pigs belonging to a local animal health official.

Nguyen Nguyen, 40, died on 10 February, just one day after the same official transferred to him the pigs that Nguyet had failed to slaughter.

Local health authorities have announced swine bacteria outbreaks in the areas where the patients lived. The patients died after developing symptoms of swine bacterial infections, including fever, diarrhea, multiple organ failure and rashes.

Quang Nam reported three swine bacteria infections last year, two of which were fatal.

Doctors said the disease is coming back after lying low for a long time.

They had earlier warned that more human infections might crop up when a large number of pigs are butchered and eaten for the Lunar New Year festival. The warnings were made in late January when three people in Da Nang neighboring Quang Nam were hospitalized with the bacteria.

There is a belief among many Vietnamese people that eating the red-colored blood dish would bring them luck in the New Lunar Year.

Doctors said the disease is dangerous as it can cause septicaemia or blood poisoning, meningitis, pneumonia and endocarditis – inflammation of the heart membrane.

They said sometimes blood poisoning does not kill, but still causes necrosis, requiring the amputation of legs or hands.

Nguyen Hong Ha, deputy director of the Hanoi hospital, said there are other complications after one is cured, such as hearing impairment, loss of memory and epilepsy.

Ha said the condition is often mistaken for dengue fever as it starts with high fever, a headache, cold feeling and rashes. "False diagnosis can delay treatment or lead to wrong treatment," he said, adding that treatment for the disease is costly at around hundreds of dollars for each case.

Globally, records show that fatalities from the bacteria are uncommon, though several have died from it in Viet Nam. One man in Hanoi died last December after eating pig blood pudding, and at least two others in central Vietnam died in 2011 after eating tainted pork.

The Hanoi hospital cited unofficial surveys as showing that around 10 to 30 per cent of the Vietnamese population are infected with the bacteria every year.

No estimations have been made about the annual fatalities nationwide but a study by the hospital in 2010, of its 55 patients, found that the death rate was nearly 13 per cent.

Ha said the hospital received more than 120 infections of the bacteria last year, with 70 per cent of the patients eating the blood dish and many among the rest eating pork that was not well cooked.

Lam Quoc Hung, in charge of poison control at the Health Ministry’s Food Safety Department, advised people to stop eating any kind of uncooked animal dish.

Dr Tran Van Ky from Viet Nam Association of Science, Technology and Food Safety, also said the uncooked blood dish should not be a tradition anymore.

"The blood carries many diseases from the animals… People eating raw blood from sick pigs can get swine bacteria, worms, and other digestive diseases, while those having blood from sick chicken can be infected with H5N1 or H1N1 viruses," Dr Ky said.

He said a large number of pigs and chicken as well as other livestock found in the market do not go through any quality control, given the widespread smuggling and loose management of slaughterhouses.

But caution should be maximized as even healthy pigs carry the bacteria, and they are also found in horses, cats, dogs and birds, doctors said.

They said butchers, farmers and vendors need to wear face masks, clean their hands thoroughly before, during and after work, and provide extra protection for scratches and exposed cuts.