The first samples of a strain of the H2N2 flu virus, which caused annual epidemics from 1957 to 1968, were sent to labs worldwide beginning in September 10, 2004 by the College of American Pathologists. Samples continued to be sent out as recently as this month, ultimately reaching 4,000 or more laboratories in 18 countries, according to the Centers for Disease Control and Prevention in Atlanta.
To date, there have been no reported human cases due to the situation, but H2N2 is feared by health authorities because it killed up to 4 million people worldwide in 1957-58. In addition, people born after 1968 -- when the virus ceased circulating -- would have little or no immunity and the strain is not included in current flu vaccines, so there is concern if it did leak out it could trigger an outbreak.
That said, the risk appears increasingly unlikely with each passing day.
"The risk is actually pretty low for laboratory workers and even lower for the public at large," WHO spokeswoman Maria Cheng told UPI.
Because the lab samples were first sent out six months ago and there have been no reports of people infected, "it makes us confident that it won't happen," Cheng said.
All of the remaining samples are expected to be destroyed by the end of the week, and at that time the agency hopes to have prepared an accurate assessment of where things stand, she added.
Dr. Julie Gerberding, the CDC director, said the agency routinely monitors specimens from people who contract the flu, searching for novel strains of the virus. So far, CDC scientists have not detected H2N2 in any of the samples they have analyzed over the past flu season, which is now coming to a close.
"For people at home hearing about this, we want to reassure you, right now, we have no evidence of any health threat," Gerberding said during a news briefing Wednesday. "We are not anticipating that there is an occult H2N2 flu circulating in the community because by now we would have been able to detect it," she said.
Gerberding emphasized that the CDC is treating the matter seriously and taking appropriate steps to ensure there is no outbreak. "While the risk is very low, we're not taking any chances and we are doing everything we can to make sure there is no threat to human health," she said.
Other experts agreed the threat is minimal.
"The real risk is close to zero," Dr. William Schaffner, a professor at Vanderbilt University School of Medicine in Nashville told UPI.
Schaffner, who also serves as a liaison representative to the CDC's Advisory Committee on Immunization Practices, noted that even if the flu virus were to spread, one advantage available today that did not exist 50 years ago, when the virus was circulating, is anti-viral drugs that effectively target the flu. So, even though people currently lack immunity to this strain, and there are no vaccines, there are other ways to fight it.
The real issue to emerge, once again, Schaffner said, is the importance of laboratory safety procedures. He noted there have been four incidents of SARS infecting people because of breaches in laboratory protocols.
"This is another human error in a lab," he said. "It reinforces the notion that every lab ought to relook and reinforce their lab safety procedures."
Even in the past, there were only a few cases of lab workers contracting H2N2, Cheng said, and added lab workers now are aware of the issue and are monitoring themselves for signs of infection.
Cheng said it was unlikely any lab workers would become infected, however, because the labs that received these samples work with flu viruses routinely and are equipped with adequate safeguards and precautionary measures.
WHO officials said in a statement that proper biosafety precautions -- such as use of biological safety cabinets and personal protective gear -- can significantly reduce the risk of transmission.
Dr. Andrew Pavia, chair of the Pandemic Influenza Task Force for the Infectious Diseases Society of America, agreed it was unlikely there would be an outbreak of H2N2.
"There are reasons to be optimistic that it won't spread," said Pavia, who also is a professor of pediatric infectious diseases at the University of Utah in Salt Lake City.
If it does happen, however, he told UPI, "it could potentially be very severe."
The situation also reinforces the need to be prepared for an influenza outbreak, Pavia said.
"One way or another a new strain of flu ... will emerge and when it does we need to be ready," he said. "We would not be ready if this started to spread across the globe right now."
Being prepared means ensuring the vaccine industry has the capacity to manufacture hundreds of millions of flu vaccine doses rapidly when an emergency arises, he said.
The incident also raises concerns about what types of dangerous organisms are in storage in laboratories, Pavia said.
"Clearly, this strain and any strain that is not in circulation should not be available for proficiency testing," he said. "What we don't know yet is why this lab (that distributed the samples) had this strain and was able to send it out. That needs to be investigated."
The CAP routinely sends out samples of flu virus to laboratories for proficiency testing as part of a process to certify laboratories, but usually the organization distributes samples of currently circulating flu strains.
In this case, apparently there was a mistake at Meridian Bioscience Inc. of Cincinnati, which sent out samples for the CAP.
Dr. Jared Schwartz of the CAP told UPI his group asked Meridian to send out proficiency-testing samples that included a strain of a currently circulating flu strain.
Schwartz said Meridian personnel obtained a flu strain from 2000 from their collection they thought fit the CAP requirements, but somehow it turned out to be H2N2. He said he did not know how the error occurred, and Meridian did not return a phone call from UPI.
"We received no feedback that there had been any problems or issues," Schwartz said.
The first laboratory to realize the CAP samples included H2N2 was the National Microbiology Laboratory in Winnipeg, Manitoba, when it identified the virus March 25 in a batch and alerted Canadian and international officials.
Schwartz said the CAP was not informed of this until April 8, when CDC officials notified them. The CDC learned of the situation when they were notified by Canadian authorities earlier that day.
Also at the time, CDC officials were in the process of deciding whether to increase the safety level required for working with influenza viruses, Schwartz said. The viruses currently are classified as Biosafety Level II organisms and officials were considering raising the rating to BSL III, he said.
The CDC concluded that for precaution's sake, all the samples should be destroyed, he added.
Gerberding said Wednesday the CDC considers the best level of protection when dealing with novel flu strains to be BSL III and "will be urgently recommending" labs use a higher level of precautions when working with any unusual flu viruses.
April 8 -- the same day it was informed about the situation -- the CAP contacted all labs that received H2N2 requesting all the samples be destroyed. The organization issued another request to the labs Tuesday, this time asking for confirmation of the destruction and to notify national authorities of any case of respiratory disease among laboratory workers.
Schwartz said he thinks nearly all of the samples have been destroyed by now.
"We've received back well over 1,000 attestation statements," he said and added he received three of the samples in his own lab -- which has destroyed them.
Although the incident was "very regrettable," Schwartz said the procedures in place at labs most likely would have prevented anybody from becoming infected.
Biolab personnel are skilled and trained in handling dangerous specimens, he said, and noted that in addition to handling flu samples they routinely handle specimens from patients infected with unknown pathogens. In such cases, personnel apply safety procedures so they would not have done anything differently even if they had known the specimens included H2N2, he said.
Almost all of the approximately 4,000 labs that received the samples are located in the United States, with 16 in Canada and 61 in other countries, including Bermuda, Belgium, Brazil, Chile, France, Germany, Hong Kong, Israel, Italy, Japan, Lebanon, Mexico, The Republic of Korea, Saudi Arabia, Singapore and Taiwan.
Schwarz said there may be other labs that received H2N2 samples. Three other groups -- the American Association of Family Practitioners, the American Association of Bioanalysts and Medical Lab Evaluators -- distributed the same H2N2 specimens used by CAP to additional laboratories, he said.