The World Health Organization has been urging thousands of labs in 18 countries which received vials of the nearly 50-year-old H2N2 virus to destroy the samples amid fears of a global pandemic should the virus be released.
WHO's influenza chief Klaus Stohr said 10 of the countries which had received samples had confirmed their labs had destroyed the virus. Labs in Lebanon and Mexico, however, "never received the specimen even though they were on the distribution list," Stohr said.
He said it was possible the shipments had never been sent out at all, but he could not be sure. WHO has requested an investigation into the missing kits, he said.
Stohr said Hong Kong, Belgium, Singapore, Canada, Chile, France, Germany, Italy, South Korea and Taiwan had all confirmed their labs had destroyed their samples of the deadly flu strain that caused a pandemic in 1957.
The 1957 pandemic strain killed between 1 million and 4 million people.