WHO fears bird flu began in April

There are concerns in some countries about cover-ups

The World Health Organization (WHO) has said the current outbreak of bird flu may have first surfaced last April, much earlier than previously thought.

Maria Cheng at the WHO would not say where tainted samples currently being tested came from, but she denied that they were from China.

The news may worry health experts, because it suggests the virus has already had time to spread widely.

Ten people have died from bird flu, but it has yet to jump from human to human.

The outbreak was first publicly reported in December, in South Korea.

But Ms Cheng said the WHO received samples two weeks ago dating back to April last year, and initial tests showed they were carrying the H5N1 virus which is now sweeping Asia.

She said that the WHO was not certain that the samples were carrying exactly the same strain as the current outbreak, but "it looks similar".

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Even if it is proved that it is not the same strain, she said, the initial results are still significant because they demonstrate that H5N1 has been in circulation for some time.

The longer it has been active, the more chances there are of humans coming into contact with infected birds.

Health experts are worried that if the virus mixes with a regular human influenza strain, it might create a mutant form that was able to pass between humans, triggering a human flu pandemic.

Ms Cheng said the WHO was not willing to say where the samples originated, but she said that they were not from China, as some media reports had speculated.

Countries in the region are under scrutiny for any possible cover-up of the virus. Thailand has already been criticised for its slow action, and the prime minister's chief spokesman has described the government's handling of the disease as a "screw up".

Culling

Ms Cheng said the WHO was still recommending culling as the best way to get rid of the "animal reservoir" of the virus.

Tens of millions of chickens and ducks across Asia have already been killed, but Indonesia initially baulked at slaughtering its chickens in infected regions, arguing that it could not afford to compensate farmers, and that it would rely on vaccination instead.

However, Indonesia reversed this position on Thursday, a move welcomed by the WHO.

Ms Cheng said that although there was still no human vaccine for avian flu, the WHO was recommending that people who come into contact with poultry get vaccinated for human influenza, as it may stop the possible combination of avian influenza with the human virus.

In other developments:

• Fresh outbreaks of the less virulent H5N2 strain of the virus has been found in Taiwan

• China is halting exports of poultry from three regions suspected to be affected by bird flu

• Tests clear a 75-year-old Hong Kong woman of bird flu, after she displayed flu-like symptoms following a trip to Vietnam

• The European Union has banned imports of pet birds - including parrots, cockatoos, budgerigars and finches - from nine Asian countries affected by bird flu.