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The “Next” Step in Bird Flu Mutations

Since its isolation in humans in 1997, Avian flu has "percolated." A few experts think that it bird flu will never make the jump to humans. On the other hand, the mainstream scientific community tends toward a cautionary position, noting that viruses have a tendency to constantly mutate.

Just a year ago, many scientists were saying that the likelihood of the bird to human jump was unlikely. But even if the current H5N1 never makes the jump to humans, there are variations and existing mutations that could.

They include H7N7, which infected 89 chicken industry workers in the Netherlands in 2003 but killed only one veterinarian; H9N2, which he says is in “every poultry house in Eurasia” and causes no symptoms but every once in a while jumps into immuno-suppressed people; and H2N2, which is in the wild bird population in the United States.

Based on the “Not if but when,” point of view, David Nabarro, a senior United Nations official in charge of the bird flu prevention effort warns that the world is not ready to deal with a potential Avian, or “bird” flu pandemic that could kill millions of people world-wide. The concern is that once the H5N1 or a variant mutates to the point where is can be transmitted from human to human, the spread around the globe will be quick, maybe outstripping the ability to develop and distribute a vaccine countermeasure.

Further, he concludes, that while some have actually been able to stockpile anti-viral vaccines, they have yet to plan for the enormous societal and economic impact a pandemic would bring. "Unfortunately, only a relatively small number are adequately prepared to keep going in the event that the pandemic has massive absenteeism associated with it, Nabarro said. We need hard work for at least two or three years more to make sure that the whole world is properly pandemic ready.”

How real is the threat of the Avian Flu making the jump to humans, and then mutating to a point where it can be spread from human to human? Back in February, I noted in a post, Preparing for a Natural Disaster of Pandemic Proportions that “the potential threat is that the difference between a flu virus that kills millions, and one that kills only a few comes down to just two amino acid changes, researchers say. In very technically medical terms:

Haemagglutinin, the main surface protein on flu viruses, binds to sugars on cells in the nose and lungs; the virus then enters the cells and replicates. Bird flu prefers a sugar called 2,3-sialic acid. Flu adapted to mammals attaches better to 2,6-sialic acid. Mammals have the 2,3 sugar deep in their lungs, but 2,6 in the nose and throat. H5N1 prefers 2,3. It had been thought that that was why it causes a devastating deep-lung infection in humans, but does not spread between people, because it does not bind and replicate in the nose.

H5N1 bird flu virus has mutated to infect people more easily and is circulating in birds in Africa and Europe. The mutation allows the virus to live and thrive in the human nose, throat, and upper respiratory tract, which are much cooler than avian body temperatures. According to researchers, more mutations are needed for H5N1 to become a pandemic strain.

Still, not too much of a concern, right? Think again. Researchers at the University of Wisconsin, Madison recently identified the key step bird flu virus takes to spread readily in humans.

A team of researchers led by virologist Yoshihiro Kawaoka of the UW-Madison School of Veterinary Medicine has identified a single change in a viral protein that facilitates the virus' ability to infect the cells of the upper respiratory system in mammals. By adapting to the upper respiratory system, the virus is capable of infecting a wider range of cell types and is more easily spread, potentially setting the stage for a flu pandemic.

"The viruses that are in circulation now are much more mammalian-like than the ones circulating in 1997," says Kawaoka, an internationally recognized authority on influenza. "The viruses that are circulating in Africa and Europe are the ones closest to becoming a human virus."

"This change is needed, but not sufficient," Kawaoka explains. "There are other viral factors needed to cause a viral pandemic" strain of bird flu.

Finally, in what shouldn’t be a surprise to anyone who has children who then bring a respiratory infection home from school and then give it to the whole family, it is reported in Science Daily that Children May Be Especially Prone to Bird Flu: Study - that the H5N1 virus may be especially good at binding to children's cells in the lower respiratory tract, as well as the upper respiratory tract of adults. The findings may explain why bird flu infects children more readily than it does adults and why it can infect the upper respiratory tract, even though tissues there were believed to lack receptors for such viruses.

Apparently, the two mutations required could be down to one. Vaccine preparation continues, with the first vaccine having been approved six months ago by the FDA (but on first reports, this vaccine didn't work all of the time, and it required high dosages). However, without any way to predict the mutation and its countermeasure, the solutions may not be that readily evident. According to the Center for Infectious Disease and Research Policy, dealing with H5N1 and its derivatives will be challenging. One path to combat this problem could be the development and use of enhanced disinfection and decontamination techniques.

Without intended self-promotion, one of my consulting clients happens to have a new technique that we are in the process of rolling out to the commercial market that could have an impact. In theory, this approach could decontaminate and sanitize the poultry population, housing and processing faciltities. And yet, this alone will not prevent an outbreak. Now if you want to get into the subject of MRSA, the technique can clearly deal with it, but that's an entirely separate topic.



I'm not certain what you mean by "make the jump to humans". The virus has already 'made the jump to humans' and has been documented as being transmitted human-to-human-to-human on many ocassions. At this point however, because of interventions from health professionals worldwide, sustained human-to-human transmission has been averted. ["On May 24, Dr. Julie Gerberding, director of the U.S. Centers for disease Control and Prevention in Atlanta, estimated that there had been “at least three”. Then on May 30, Maria Cheng, a spokeswoman for the U.N. health agency said there were “probably about half a dozen.” She added, “I don’t think anybody’s got a solid number.”

"And Dr. Angus Nicoli, Chief of flu activities at the European Center for Disease Prevention and Control, Stockholm, acknowledged that “we are probably underestimating the extent of person-to-person transmission.” “The handful of cases usually cited, he said, are “just the open-and-shut ones, “like the infections of nurses in the 1997 Hong Kong outbreak and of a Bangkok office worker who died in 2004 after tending her daughter who fell sick on an aunt’s farm.”(Donald G. McNeil Jr., THE NEW YORK TIMES, Sunday, June 4, 2006.)]
["The problem is that this virus already has the ability to infect humans, so it's one step closer than anything we've seen before," said Robin Robinson, acting associate director for pandemic influenza medical countermeasures with the Department of Health and Human Services. "The viruses are one to two mutations away from sustained human-to-human transmission." "As the virus continues to evolve genetically and acquires by mutation the ability for sustained human-to-human transmission, then an H5N1 pandemic may emerge," Robinson said. "When will this event occur is not known, but the virus does continue to evolve and does represent a significant pandemic threat." (Will U.S. finish preparing for flu pandemic before clock runs out? Latest News and Developments, 17 Mar 2007)]

Yes, Mel, H5N1 has already infected people. It hasn't (yet) reached the pandemic proportions that some fear and others predict. And more importantly, it really hasn't gone to the point where human-to-human transmission is prevalent. While maybe it wasn't expressed as clearly as I thought, the work published by the researchers at the University of Wisconsin is clear in its implications that the morphing of the virus is occuring in such a manner that it will cross that line of human to human to human transmission.

The mutative process is normal and expected. When the final change required to create havoc is not known.

Your points are well taken, and I'll read your references more closely later on. If you have more information or a more focused point of view, please share. I'm not in the medical profession (obviously), but I am interested in the future onset of a pandemic flu outbreak from the standpoint of how the infected or affected areas will respond.