Vietnamese bird flu lurks in wings for time to strike

By MARGARET HARRIS, Herald Correspondent


VIETNAM - Get on a plane out of Hong Kong and the fear is palpable. The masks are noticeable, temperature scans are thorough and medical cards collected and checked.

But get off that plane in Vietnam and you might think the threat has evaporated. There are temperature checks but the masks, the lines of health monitors and that formless anxiety that cloaks Hong Kong travellers are conspicuously absent.

All the interest seems to be in setting up to celebrate Tet - the Vietnamese Lunar New Year.

True, the fear in Hong Kong is all about Sars. Vietnam has never been as paranoid despite suffering a significant outbreak of the virus last winter. But in Vietnam, bird flu, a disease experts fear even more than Sars, is doing its best to evolve from a significant health threat into a major human disaster.

"Nature is getting the better of us," said Professor Ken Shortridge, the man who first identified the avian flu virus in Hong Kong in 1997 - now retired in New Zealand. "It's there all the time it lurks. I don't think we've had this before in the world, viruses potentially dangerous to humans waiting to spread."

Shortridge believes that, because Sars and this new strain of bird flu are both trying to get into humans at the same time, the pressure on humans and health systems could reach a critical level. The symptoms of Sars and the bird flu are similar: high fever, sore throat, a cough, aches and pains, exhaustion. But the treatment (there are effective anti-flu drugs available and vaccine production is at a more advanced stage than for Sars) is very different.

And the two spread very differently. So sorting out whether Sars or bird flu or both are emerging is critical, says Shortridge. "The world could face a catastrophic situation. Sars will help to beget flu and the two will act in tandem."

So why is Vietnam so calm? Because so far the threat is more theory than practice. The practice is centring on eradicating chickens, the reservoir in which H5N1 is held, hoping to remove that stronghold before it can borrow enough genes from human flu viruses to make humans a new and much better home for itself.

Right now the H5N1 isolated from three of the people who have died in Hanoi with symptoms suggestive of bird flu is "purely avian" says Dick Thompson, spokesman for the World Health Organisation's communicable diseases centre in Geneva.

Keeping the virus that way: purely a bird infection able to get into humans unlucky enough, (or in adult cases careless enough when handling chickens) is what all the excitement is about.

It really is a race between man and virus this time. And the virus has got a number of things in its favour. First, it appears to have really taken hold in North and East Asia - infecting flocks in Japan, Korea and Vietnam.

And although a particularly vicious version ravaged flocks initially in southern Vietnam, the actual human infections have all occurred in the Vietnamese capital, Hanoi. When these infections first appeared - and ironically it was the fact doctors were on alert for Sars that they took serious note of a number of children dying of a pneumonia associated with a high fever from the end of October to early January - no one was talking about chickens getting sick.

But, says Dr Pascale Brudon, head of the WHO in Hanoi, after talking to the families of some of the children who died, it turned out all had noticed their chickens sicken and die around the time the children got infected.

Which means bird flu could be jumping into humans throughout Asia. It may have done so already without being noticed in other places where the flocks are infected.

And the more time it has to acquaint itself with human systems and human flu strains, the better it gets at turning itself into something able to spread through human populations the way it does through chickens.

The first case appeared in October but it was not until more children died the health authorities turned to the WHO, who in turn sent samples from six suspect cases to Hong Kong for testing. Three of those have come back positive-while the other three are being further tested.

Though they are all called H5N1, the one in Hanoi is slightly different from the strain which emerged in Hong Kong in the spring of 1997, first in a young boy who played with chickens in his kindergarten classroom, then later in a cluster of people. By the end of the year, six of 18 infected people were dead, and chickens in markets and farms around Hong Kong were testing positive for the virus. At a crisis meeting it was decided the only way to avert a potentially global epidemic was to kill every chicken in Hong Kong.

It was chance that saw an unidentified virus isolated from the first case because someone went looking for viral causes of this high, and ultimately lethal, fever.

The virus sample was sent to the University of Hong Kong's laboratory where Shortridge, who had devoted a career to the study of influenza viruses, suspected the virus might be a bird virus and sent the samples off to the US Centre for Diseases Control for an opinion.

Their answer: yes it was something new. But until a few more people, then more and more started developing symptoms and were indeed found to have bird flu, the very real danger the world faced was not understood.

By Christmas, Shortridge and his colleagues believed the only thing that stood between an outbreak and a global pandemic was the fact the thing still had not got hold of enough human flu virus genes to re-assort itself and find a way to jump from human to human.

It needs to be able to get into respiratory epithelium - the cells lining the mouth, throat and lungs where human flu viruses grow. The bird flu viruses live in the gut or get into the bloodstream so spread via direct contact with chicken faeces or blood. But the human version gets exploded out as aerosols by coughs and sneezes and can float through crowded rooms.

The flu is better at shifting and changing to adapt itself at better and better living homes.

Shortridge explains that all the versions of influenza get together with different partners and mate passing on bits from each other to their offspring.

This constant viral party and the vast array of "offspring" means flu is maximising its chances of producing superflu. And that is the one whose birth the experts are doing their best to prevent.

But to prevent it getting the chance to turn itself into superflu tough decisions and serious changes are necessary on eating and living. Fresh chicken may be off the menu forever.

Country on alert

* The World Health Organisation has raised the number of Vietnam's confirmed bird flu deaths to four.

* A 5-year-old boy who died this month was found to have been carrying the virus.

* The UN health agency, which is helping Vietnam battle the fast-spreading disease, said the boy was from Nam Dinh province, about 100km south of Hanoi.

* Vietnam has a total of 18 suspected cases of bird flu in humans, all in the north, with 12 deaths.

* Eight of Vietnam's flu deaths are still being investigated for bird flu links.