Scientists in 18 countries are tracking down and destroying thousands of vials of a lethal virus that, if it escaped, could trigger the long-feared global flu pandemic, the World Health Organization said Wednesday. The samples of virus H2N2, which caused 4 million deaths in the 1957 flu pandemic, were sent to more than 3,700 laboratories by a leading American medical institution several months ago.
Wednesday, it emerged that the potentially deadly distribution was discovered only through a combination of luck and human error at a laboratory in Vancouver, Canada. The original mistake was made in October of last year in Northfield, Ill., a suburb of Chicago, home to the headquarters of the College of American Pathologists.
The college sends out standardized flu-testing kits to labs around the world, each containing vials of different strains of flu virus to enable technicians to ensure that their own testing equipment and reagents are working properly. This time, included with the modern strains of flu virus was the killer Asian flu known as H2N2.
The virus went to Belgium, Bermuda, Brazil, Canada, Chile, France, Germany, Hong Kong, Israel, Italy, Japan, the Korean Republic, Lebanon, Mexico, Saudi Arabia, Singapore, Taiwan and labs in the U.S.
In Vancouver, British Columbia, technicians ran a sample from the panel containing H2N2 under the same flume hood as a sample from a patient -- a practice that would not be allowed in many laboratories because of the risk of contamination, Frank Plummer, director of the National Microbiological Laboratory said. The patient sample became contaminated. "The panel sample has a very, very high level of virus," Canada's chief public health officer, David Butler-Jones, said. "There was enough that it gave a low-level positive result in the patient sample."
Plummer went on to reveal that the patient in Vancouver was not suffering flu symptoms, and that the test was administered as a matter of routine. The sample then was forwarded to the national laboratory -- again a matter of pure chance, as regional facilities generally send only 25 percent of their samples for the more detailed analysis capable of identifying the flu strain as the deadly H2N2. "There is certainly a kind of irony here," Plummer said yesterday, "but it is a happy sort of error."
The result -- indicating the presence of H2N2 in a human for the first time in nearly 40 years -- triggered an investigation. The patient was retested and found not to have H2N2, and the source of the contamination was traced to the panel on March 26.
Klaus Stohr, who heads the World Health Organization's influenza program, said the virus could cause a global flu outbreak. "It was an unwise decision to send it out," he said.
Asian flu did its deadliest work in 1957, until populations began to develop immunity to it and vaccines were developed. The strain lingered until 1968, vanishing as the next pandemic arrived -- Hong Kong flu, or H3N2. This means that people born after 1968 have not developed immunity to H2N2.
John Oxford, a professor of virology at the Queen Mary School of Medicine in London, said this could pose a problem to the labs that received the testing kits: "You tend to give this kit to the youngest, most unqualified person because it is all very simple," he said. "That young person is the most susceptible. Anyone younger than 36 or 37 would have no immunity."
The WHO said there was no need to panic: "It is a risk, but it is considered low. It should not lead to a big scare," Dr. Stohr said. Professor Oxford agreed, but said that if labs knew they were dealing with H2N2, they would treat it with greater respect than other strains. "It is a potential pandemic virus," he said. "If somewhere in the world it gets out, it will be on our doorstep tomorrow morning."
The kits were usually sent out in the ordinary mail, he added. "We are allowed to send viruses in the post as long as they are wrapped in absorbent paper."
Some labs may not have thought the arrival of H2N2 remarkable, he said. "Most labs would say, 'Oh yes, an old-fashioned virus.' But at the cutting edge of influenza, there is already uncertainty about H2N2 and discussions about it and the feeling that it might turn into a pandemic and we should be careful."
There were two pieces of good news, he said: that this would make labs more careful with H2N2 and that the British government had stockpiled the drug Tamiflu, which works against this strain.
Canada may have been the first country to realize the potential danger, because it is particularly on the alert and prepared for emerging diseases after the SARS outbreak. After the discovery, the Public Health Agency of Canada alerted the WHO, which instructed all laboratories to seek out and destroy all stocks of H2N2 received in testing kits from the American college.
Wednesday, the four European countries that received the virus -- Germany, France, Belgium and Italy -- moved swiftly to destroy it. Health officials in Germany said the U.S. company had supplied six laboratories with the virus in the states of Bavaria, Baden-Wurttemberg and Rheinland-Palatinate. The labs destroyed the samples Wednesday, officials said, after a directive from the country's health ministry.
Susanne Glassmacher, a spokeswoman for the Robert Koch Institute in Berlin, said: "The risk for the general population is very slight. The labs that got the H2N2 virus are used to dealing with dangerous virus samples. These are experienced diagnostic laboratories, and they don't always know what they are getting. They are always pretty careful."
According to health officials in Europe, the laboratories had been expecting to receive the far more common strain of modern flu virus H3N2. It was not clear Wednesday night whether the laboratories were aware before the alert was issued that the samples contained the far more dangerous 1957 H2N2 strain.
According to the WHO, four countries have destroyed all their stocks -- Canada, Hong Kong, Singapore and Korea -- while Taiwan was moving quickly to do the same. In America, where the bulk of the virus samples were sent, Julie Geberding, director of the Centers for Disease Control, said, most laboratories have destroyed their samples.