Bird flu 'very low' risk to humans

EXPERTS have played down fears that the bird flu strain could ultimately mutate to a type easily passed between people.

EXPERTS have played down fears that the bird flu strain could ultimately mutate to a type easily passed between people.

At the moment not a single case of bird flu reported across the globe has been a result of human to human contact.

Scientists said it was rare for an animal virus to cross the species barrier and only those in close contact with diseased birds are at any risk.

Last year Sir David King, the Government's top scientific adviser, said the risk of bird flu developing into a form that could pass between humans was “very low”.

Four types of the virus in birds are known to have caused infections in humans. These are known as H5N1, H7N3, H7N7 and H9N2.

Generally these lead to mild symptoms and not many cases of severe illness.But there is one notable exception - the H5N1 strain, which can lead to serious illness and death.

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It is this virus which has infected more than 250 people, mainly in south east Asia, and caused 164 deaths between January 2003 and September 2006.

But all these cases resulted from close contact with wild birds and poultry and no infections have been spread from person to person.

Symptoms include a sore throat, aching muscles, lethargy, eye infections, breathing problems and chest pain.

Deterioration in patients with H5N1 can happen very quickly and within a few days they can be dead.

By far the greatest concern has been that the bird flu virus will change into a form that is easily spread between humans, leading to a flu pandemic.

There are two main methods which could cause this to happen. The first is by “reassortment” whereby genetic material is exchanged between human and avian viruses during co-infection of a human or pig.

In this mechanism the human could act as a mixing pot, with the human flu virus mixing with the avian flu virus and creating a fully transmissible pandemic virus.

The second mechanism would involve a more gradual process of mutation, with the virus adapting so it was more successful in infecting humans.

But experts fear that it is only a matter of time before a new flu pandemic emerges, with bird flu its most likely initial source.

Pandemic flu spreads rapidly to affect most countries and, unlike ordinary flu which occurs every winter in the UK, it can emerge at any time of year.

It is thought that few people, if any, would have any immunity to a new pandemic virus, allowing it to spread widely and to cause more serious illness.

The Government has already developed a flu pandemic action plan and taken other measures to try to prepare for when it happens.