Channel NewsAsia 8 Apr 08;
PARIS: A 24-year-old man in China probably infected his father with the H5N1 strain of bird flu before dying, renewing concerns that the disease could one day spread easily among humans, according to a study released on Tuesday.
The case is one of a handful over the last four years in which the H5N1 virus is suspected to have spread from one person to another, according to lead researcher Yu Wang of the Chinese Centre for Disease Control.
To date, however, all such cases have been what scientists call "limited, non-sustained, person-to-person transmission," meaning that contagion only occurs under very specific circumstances.
The vast majority of the known 378 human cases of H5N1 bird flu since 2003 were spread by domestic or wild fowl, according to the World Health Organisation. More than 60 percent proved fatal.
"It is not normal social contact that has led to the human transmission," epidemiologist Jeremy Farrar, a researcher at the national Institute of Hygiene and Epidemiology, told AFP in an interview.
"In this case it took extensive exposure to secretions of somebody who was very sick in hospital," he explained.
Another limiting factor may be genetic, the study found. The suspected cases of human-to-human transmission have all been "within the family, among blood relatives", said Farrar.
None of the 91 persons besides the father who came into contact with his son before he died showed any sign of infection, said the study, published in the British medical weekly The Lancet.
Nor was there any significant genetic variation between the viral strain in the father or the son.
Experts fear that the H5N1 virus could mutate after infecting one human into a more contagious form, as occurred during at least three flu pandemics in the 20th century.
An estimated 20 to 40 million people perished in the so-called "Spanish flu" of 1918.
Any new clusters of the virus "require urgent investigation because of the possibility that a change in the epidemiology of H5N1 cases could indicate that H5N1 viruses have acquired the ability to spread more easily among people", said Wang.
The two cases examined in the study were identified in December in the city of Nanjing, in China's Jiangsu Province.
Since 2003, there have been 107 H5N1 bird flu fatalities in Indonesia, 52 in Vietnam, 20 in China, 17 in Thailand, and between one and seven in seven other nations. AFP/so
Father 'caught bird flu from son'
BBC News 8 Apr 08;
Tests on a father diagnosed with bird flu in China show he probably caught the disease from his dying son.
Scientists are concerned that if the virus evolves to pass easily from human to human millions could be at risk.
A genetic analysis of the Chinese case published in The Lancet found no evidence to suggest the virus had gained that ability.
But an expert has warned that failure to control outbreaks of disease in poultry is fuelling the risk to humans.
Writing in The Lancet, Dr Jeremy Farrar, of Vietnam's Hospital for Tropical Diseases, said: "Whatever the underlying determinants, if we continue to experience widespread, uncontrolled outbreaks of H5N1 in poultry, the appearance of strains well adapted to human beings might just be matter of time."
However, he said a pandemic was by no means a "biological inevitability".
So far 376 cases of human infection with the H5N1 form of bird flu have been recorded in 14 countries since November 2003, mostly in South East Asia.
There have been 238 recorded deaths from the virus, of which a quarter have come in clusters of two or more linked people.
At present H5N1 remains overwhelmingly a disease which affects birds, and the only humans at risk appear to be those with regular close contact with infected animals.
But the researchers, from the Chinese Centre for Disease Control and Prevention, warn that clusters of H5N1 human infections require close scrutiny to determine whether the virus is starting to evolve into a more potent threat.
Father survived
The Lancet study highlights the case of a 24-year-old man, from Nanjing, in Jiangsu Province, who died from bird flu.
It is thought he passed the disease on to his 52-year-old father, who survived after receiving prompt medical attention, including anti-viral treatment, and plasma cells from somebody who had been vaccinated against the disease.
It is believed the son caught the disease during a visit to a poultry market six days before he became ill.
Medics also tested 91 people who had come into contact with the infected men, but none of those had contracted H5N1.
The researchers say the possibility that the father caught the disease independently cannot be completely ruled out, but think it unlikely.
Other cases of suspected human-to-human transmission have also been between blood relations.
This may be because related individuals share a genetic susceptibility to infection.
Professor Ian Jones, an expert in virology at the University of Reading, said the fact that the father was the only person to be infected was encouraging.
"The virus isolated had no changes to indicate adaptation to human infection," he said.
"There is no indication from this data that we are any nearer a pandemic."
Professor Wendy Barclay, of Imperial College London, agreed there was no evidence to support the idea that H5N1 had acquired mutations that make it more dangerous to humans.
"The experience here reinforces the idea that there are still several barriers the virus must overcome before it acquires human transmissibility."
