The World Health Organization says health experts have destroyed two-thirds of the specimens of a killer influenza virus that were inadvertently sent by U.S.-based medical organizations to laboratories in the United States and many other countries.
But it says it is investigating the whereabouts of two missing shipments that were supposed to have gone to Lebanon and Mexico.
The World Health Organization says laboratories around the world have responded very quickly to its request to destroy the dangerous flu strain, called H2N2.
The head of WHO's Global Influenza Program, Klaus Stohr, says 12 of the 17 countries outside the United States report they have destroyed all the samples they received. He says no information has yet been received from Bermuda, Brazil, Israel and Japan.
But, he says he is confident they will also destroy the samples.
"Two-thirds of the material has already been destroyed and the rest of the material is also, hopefully, subject to destruction very fast. Our level of concern has certainly gone down. But, I do not want to say that we have not been at least surprised, very surprised to hear about the distribution of a strain with pandemic potential."
The H2N2 virus is similar to one that caused a global influenza outbreak in 1957, killing between one million and four million people. The virus disappeared in 1968. Anyone born after that time would have no immunity. If the virus got loose, the World Health Organization says it could spark another pandemic.
The deadly flu strain was sent to more than 37,00 laboratories in the United States and 17 other countries in February as part of a routine testing procedure. The dangerous virus was detected at the end of March by a laboratory in Canada and it immediately informed the World Health Organization.
Dr. Stohr says he expects all the international laboratories that received the specimens will have destroyed them by Friday. However, he says test kits sent to labs in Lebanon and Mexico appear to have been lost and that finding them is a high priority.
Dr. Stohr says as a result of the shipment of the killer virus, the World Health Organization is reviewing its international bio-safety standards and plans to come up with new recommendations by the end of the month.