AVIAN flu may be much more common than anybody realised, Oxford scientists have given warning, and could have caused deaths without its involvement even being suspected.

The detailed investigation of the deaths of two children in Vietnam has found that the avian flu virus can cause a disease that bears little obvious resemblence to flu.

The children — a girl aged nine and her brother, who was four — went into a coma and died within a few days of falling ill. They came from Dong Thap Province in southern Vietnam, and both were recorded as having died of acute encephalitis — inflammation of the brain.

Neither had any respiratory illness or evidence of pneumonia until the last 24 hours of their lives, and neither death was linked to the avian flu virus.

But a study published in New England Journal of Medicine of samples from the boy show that he was heavily infected by the avian flu virus. It is assumed that his sister, who died two weeks earlier from identical symptoms, was also infected by avian flu but samples were not saved and so cannot be tested to confirm this.

The post-mortem samples from the boy show that he had the flu virus in his faeces, blood, nose and in the fluid around his brain, indicating that the H5N1 avian virus can affect all parts of the body, not just the lungs.

The investigation was led by Menno de Jong, virologist at the Oxford University Clinical Research Unit, based at the Hospital for Tropical Diseases in Ho Chi Minh.

He said: “This illustrates that when someone is suffering from any severe illness we should consider if avian flu might be the cause.

“It may be possible to treat, but you have to act in the early stages, so awareness of the whole spectrum of symptoms in an emerging disease like avian flu is vital.

“It appears this virus is progressively adapting to an increasing range of mammals in which it can cause infection, and the range of disease in human beings is wide and clearly includes encephalitis.”

Jeremy Farrar, director of the Vietnam unit, which is backed by the Wellcome Trust, said: “This latest work underlines the possibility that avian influenza can present itself in different ways.

“The main focus has been on patients with respiratory illnesses but clearly that's not the only thing we should be looking for. Therefore the number of cases of H5N1 may have been underestimated.

“The presence of virus in the faeces also highlights a potential route of human-to-human transmission, especially in crowded living conditions, which is a major cause for concern and has important implications for infection control and public health." How the two children caught the disease is not clear. They lived in a one-room house in a hamlet with their parents, who had no other children, and who did not catch the disease.

The family did not keep chickens, but did have healthy fighting cocks. Near the home was a canal, whose water was used for washing clothes and in which the girl often swam. There were also domestic ducks living in the canal, and they may have been the source of the infection.

Direct transmission of the infection between the two children appears unlikely, because they fell ill ten days apart.

But the discovery of the virus from the boy’s faeces “is a major source of concern, since it highlights a potential route of human-to-human transmission, espcecially in combination with crowded living conditions and diarrhoea,” the team says.

Both deaths happened a year ago, but the involvement of the avian flu virus was not suspected until detailed analysis of samples from the boy late last year.

Gastroenteritis and acute encephalitis — the symptoms the children showed — are common in Vietnam. It is therefore possible that there have been many unrecognised cases of avian flu in the country, and also some unrecognised deaths.

2OTH-CENTURY PANDEMICS

• 1918-19 The so-called Spanish flu (H1N1) triggered the worst flu epidemic yet, taking more lives than the First World War. Estimates for the global death toll range from 20 million to 40 million, including more than 200,000 in Britain. Nearly half of those who died were young, healthy adults, and the disease killed many within a few days

• 1957-58 Asian flu (H2N2) killed about one million worldwide. First identified in China in late February 1957, Asian flu spread to Europe and the US and caused millions of infections. In Britain one in six people caught it and 30,000 died

• An abrupt shift in flu strains, similar to those that preceded the pandemics, would reveal the hidden power of the disease

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