'Bird flu' deaths in Hong Kong spark fears of global epidemic

Ten days ago a boy in Hong Kong, aged nine, fell ill with flu. Normally such an event would not rate a passing mention. But this was no ordinary flu.

Yesterday the World Health Organisation (WHO) confirmed the strain as A (H5N1), also known as "bird flu". They fear it could become a global killer.

The boy's father and sister have already died. They were suffering similar symptoms, although their illness has not yet been confirmed. The boy's mother also fell ill but she has recovered. The boy himself has been treated in hospital since 12 February and is reported to be in a stable condition.

Experts around the world are now anxiously awaiting the outcome of further tests, which will determine what the virus is likely to do next. In the worst- case scenario, this could be the start of the world's next flu pandemic.

In a statement issued yesterday, the WHO in Geneva said its global influenza network had been alerted and it had offered to provide support to the medical authorities in Hong Kong. A spokesman said last night: "This is a potentially serious situation. The global network has been working overtime with constant conference calls. They have been trying to work out what assistance they [in Hong Kong] need and what we can provide."

Scientists have predicted for more than a decade that a new strain of flu could cause a global pandemic at any time. The flu virus mutates constantly and each year's outbreak is caused by a slightly different virus from the previous year. But once in a generation, a major mutation produces a wholly new virus to which the population lacks immunity.

Three times in the past century, major mutations have caused pandemics of flu, the worst of which was in 1918, when millions of people died. More people are estimated to have died in that pandemic than in the two world wars combined. The latest pandemic was in 1968. Scientists have said since then the question is not whether it would be repeated, but when.

In response to the threat, the British Government has drawn up contingency plans. A measure of the seriousness with which the authorities view the threat is that the plans include temporary measures to increase mortuary space.

Whether the new case of "bird flu" is the start of the next pandemic cannot yet be said, but experts are taking no chances. The first outbreak of the strain A (H5N1) was in Hong Kong in 1997 when 18 people were infected and six died. That was the first time the strain, common in chickens and ducks, was seen in humans.

In December 1997, all chickens in Hong Kong, which were thought to be the source of the outbreak, were slaughtered and no further cases were reported. Since then the authorities have maintained intensive surveillance for the next outbreak of the virus. Yesterday they found it.

The virus identified in 1997 was extremely nasty. It killed one third of the people who were infected. But it had a critical weakness. It did not appear to be transmissible between humans.

Scientists believe that the 18 people who became infected in 1997 caught it directly from chickens. That made it much less of a threat to the wider population because it was likely to affect only people who lived in close contact with the birds.

Once all chickens were slaughtered and disposed of in Hong Kong the outbreak petered out.

To cause a pandemic, a flu virus must be both deadly and infectious. What is already clear is that the new strain of A (H5N1) is deadly. But is it infectious? According to the WHO, the boy now lying in a Hong Kong hospital travelled with his mother and two sisters to Fujian Province in China in January. One of his sisters, aged eight, became ill while the family were there on 28 January. She was admitted to a local hospital and died seven days later on 4 February.

The boy's father joined the family, after his daughter became ill, on 31 January. He fell ill himself a week later, on 7 February. He returned to Hong Kong where he was admitted to hospital on 11 February. He died five days later.

Doctors in Hong Kong are now working to establish whether the boy's father and sister died of the same strain of flu that infected the boy. They will also try to establish the source of the infection.

The WHO spokesman said yesterday: "If this virus is transmissible from human to human then it is far more serious. It will be taken apart genetically. We will then be able to tell if it is exactly the same as in 1997 or whether it has changed genetically and what the significance of any changes are.

"We should know if there have been any changes in the next few days but understanding their significance is going to take more time."

He added: "We have got people in Hong Kong who have experience of this – we couldn't ask for a better team."

Professor John Oxford, an expert on flu at the Royal London and St Bartholomew's NHS Trust, said last night: "The question is, has this virus been transmitted within that family or have they all got it from a common source? I think it is worrying. It does look as though there has been some transmission. If so, it will be the first time that has happened with this virus." But if confirmation comes in the next few days that the virus had spread within the family, that would not necessarily mean the virus could spread beyond them, he added.

"The family is a small, close-knit environment. If the virus has jumped the huge barrier from chickens to humans, it may be able to jump the smaller barrier from human to human within the family but it may lack the extra punch it needs to break out of that small group. It may not yet be Armageddon," he said.

A spokesman for the UK Public Health Laboratory Service said that specialists were scheduled to meet World Health Organisation experts later this week to discuss the Hong Kong outbreak.

"We are waiting for more information. We don't know enough to make a comment at the moment," he said.

Worst outbreaks of past century

1918 Spanish flu pandemic

The 1918-19 Spanish flu pandemic was the worst of the last century. It was caused by the H1N1 strain and killed more than 20 million people. It preyed on mainly young, healthy adults and struck between 20 and 40 per cent of the world's population in almost every country. An estimated 250,000 Britons were struck down. Death usually came from bronchitis, pneumonia or the virus overwhelming the lungs.

1957 Asian flu pandemic

This bug did not cause as much damage as the 1918 pandemic thanks to scientific advances. The bug was identified in the Far East in February and by May vaccine production began. But in the UK, there was still an estimated 30,000 deaths and one in six people caught it. In the United States, there were close to 70,000 deaths. The elderly had the highest rates of death. An estimated two million people died worldwide.

1968 Hong Kong pandemic

Caused 78,000 deaths in two waves in the UK and 34,000 deaths in the US. Infected eight per cent of the British population. Caused by the H3N2 strain, it led to one million deaths worldwide. It was first identified in Hong Kong in early 1968 and those over 65 were most likely to die. The virus returned in 1970 and 1972. Improved medical care and antibiotics helped to prevent more deaths.

Andrew Clennell