Researchers refine theory for lab origin of swine flu

By Peter Duveen

PETER'S NEW YORK, Tuesday, September 22, 2009--The swine flu that is making its rounds throughout the world has signs it was produced in a laboratory, say two researchers, although a theory that the virus had been circulating undetected among swine for some time before jumping to humans has not been ruled out.

According to a research note circulated by two virologists, Adrian J. Gibbs and Jean Downie, the signs that point to a laboratory origin of the swine flu are that it came from three parent viruses, all from disparate parts of the world, and that the last time these parent viruses were sampled in pig populations was from eleven to seventeen years ago.

Gibbs and Downie contend that the swine flu's triple parentage would only have been possible with the breaking of quarantines of infected pigs and their transport in some combination among three continents. More probable, they say, is that samples of the viruses had been kept in a laboratory, where they were allowed to combine. One of the parent viruses was sampled among pig populations in the United States but never in Europe. Another was sampled in Europe but never in America. A third was found in Southeast Asia. The fact that the American parent virus had never been sampled in Europe, nor the European virus in America, Gibbs and Downie say, is evidence that pig quarantines in those regions had not been violated.

The other unusual property of the parent viruses of the swine flu is that the last time each was sampled was at least eleven years ago, and in one case, 17 years ago. That begs the question of why all three should have suddenly and simultaneously combined to form a new virus now, and why they they were not detected in infected pig populations for so long. The research note indicates that this can be most easily explained if samples of the viruses had been sitting in a laboratory refrigerator since they were last gathered from infected populations more than a decade ago.

The two scientists believe that the most likely scenario for the emergence of the swine flu was in the process of preparing a vaccine from the three parent viruses. The viruses must first be grown in hen's eggs, then chemically sterilized to prevent them from multiplying in the vaccine recipient. If the viruses had not been completely sterilized, they could have multiplied and combined to form today's swine flu, the authors say.

The research note indicates that the swine flu must have become highly contagious just before it was first detected in human populations in the Spring. Had it been contagious earlier, it would have been detected earlier, explain Gibbs and Downie.

The note mentions a recent paper in the scientific periodical Nature which proposes that the flu had existed for a long period of time in pig populations, but had not been detected because of lax monitoring.

Gibbs and Downie say enough information is not available to decide between the two hypotheses. The information needed would be a complete inventory of samples of flu viruses in laboratories throughout the world, to see if the parent viruses are among them, along with a check to determine whether there is any evidence of pig quarantines being compromised. The effort to determine the origin of the swine flu would be worth it, the authors contend.

"Influenza is a significant and very costly cause of mortality and morbidity in the human population," say Gibbs and Downie.  "If we wish to avoid new outbreaks rather than just minimizing the damage they cause, we must better understand what conditions produce them."

Gibbs, who has published more than 200 scientific papers and is an expert in viral evolution, achieved notoriety in the Spring when he first put forth his hypothesis that the swine flu, which emerged in Mexico in April, had a laboratory origin. Officials of the World Health Organization said they had examined his hypothesis, but decided the phenomena Gibbs cited in support of his thesis could be explained in other ways. In an interview with Peter's New York after the WHO released its findings, Gibbs said he found the WHO's arguments rejecting his hypothesis unconvincing. He and Downie have since submitted an updated paper to a scientific journal, and are awaiting word of its publication.