THOUSANDS of laboratories have been ordered to destroy samples of a flu virus sent to them to test their competence.

The World Health Organisation (WHO) said that the samples should never have been dispatched because they had the potential to trigger a pandemic. “We are concerned,” Klaus Stohr, the WHO’s leading flu expert, said.

The organisations that sent out the samples — the College of American Pathologists and a company called Meridian Bioscience, acting on its behalf — indicated that it had been a mistake. Dr Stohr said that it was intentional and, although not illegal, unwise.

The 1957 Asian flu pandemic was caused by type A influenza, of the H2N2 subtype. Since 1968, when the H2N2 strains were replaced by a different subtype, populations have not been exposed to H2N2, so few people have immunity.

The samples were part of a quality-control programme testing pathology laboratories’ ability to carry out routine tests. They are among hundreds of differnet samples sent out on a regular basis and went to about 5,000 laboratories. The risk was that a laboratory worker would contract the flu and start an epidemic. As few people have immunity, the results could have been serious.

Dr Stohr said that the virus killed between 1 million and 4 million people in 1957. “It could cause a global flu outbreak,” he said.

“It was an unwise decision to send it out. It should not lead to a big scare.” He hoped that the samples would be destroyed by tomorrow.

The majority of the samples went to American laboratories, but some went to Saudi Arabia, Jamaica, Mexico, Lebanon, Brazil, Hong Kong and Italy.The discovery that the virus was the H2N2 Asian flu was made by a Canadian laboratory on March 25. The National Microbiology Laboratory in Winnipeg identified it but because it had been contaminated by other flu samples, the proficiency kit was not identified as the source until last Friday.

The WHO was notified and it issued instructions to the laboratories that the vials should be destroyed.

H2N2 virus, which was considered mild, would quickly have been picked up by health authorities if there had been any contagion, Dr Stohr told a news conference in Geneva.The WHO said that it had delayed going public with the news so that the laboratories could have time to make the samples safe.

A spokesman for the college said that Meridian had been asked to ship a type A flu virus, and its paperwork indicated that the strain it had sent out was not dangerous. For reasons that neither the college nor the company understood, he told the Washington Post, the documentation had been incorrect.

Samples of bacteria and viruses are widely used in research laboratories.

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