By Gregory Mott
Washington Post Staff Writer
Tuesday, October 18, 2005
Avian flu is an imminent threat to health and well-being. For birds. In Asia and Eastern Europe.
That reality is easily missed in the face of warnings from government officials and public health experts of an impending global pandemic that could take millions of lives, devastate economies and require militarily-enforced quarantines.
The highly virulent strain of influenza that is devastating bird populations in Asia is arousing concern among medical experts because the disease has proven to be transmissible from infected birds to humans with lethal consequences -- 60 of the 117 confirmed cases in humans have been fatal, according the World Health Organization (WHO). But nearly every human case has resulted from direct contact with an infected bird, and at this point the virus does not transmit easily from human to human.
That doesn't mean there's no cause for concern. Experts worry that the bird flu virus could mutate in a way that would make it more easily transmissible from person to person. The WHO notes this is more likely if a large outbreak among animals occurs during the human flu season.
Efforts to contain bird flu range from monitoring bird populations to expediting research to develop a vaccine for broad use should the disease begin to spread among humans. John Treanor, a professor of medicine at the University of Rochester and lead investigator in a National Institutes of Health-sponsored trial of a prospective avian flu vaccine, addressed questions in a telephone interview.
Recent reporting on the avian flu seems to suggest that a human pandemic is inevitable. Is that the case?
Well, I don't like the word "inevitable." I think there is a real possibility that we will have a pandemic of flu due to one of these bird flu viruses . There are a lot of things we don't know about the epidemiology of flu and how flu pandemics get started. I think it is definitely something that we need to take seriously and worry about and be prepared for, but I don't know that it is inevitable.
Your work is aimed at developing a vaccine that would help protect against spread of the disease. How would such a vaccine be used?
We are testing a prototype vaccine that is designed to be very similar to a regular flu shot but that contains the components of bird flu. And we're looking at that vaccine to see that it's safe and also to determine the best dose to use and to look at what the immune response to the vaccine actually is.
If it were to work out, it would be given prophylactically in much the same way as the regular flu shot. The specific target groups would depend in part on what the supply was and in part on what was judged to be the risk at the moment.
I suspect that the rollout of a vaccination campaign, were that to happen, would be phased with an initial targeting of certain groups, and then a wider use later.
Would the high-risk groups that get the regular flu shot first also be first in line for the avian flu vaccine?
I think it would probably be very similar, but perhaps it would be a little bit more shaded toward health care workers and first-responder types than the way we use the current vaccine. We currently recommend that all health care workers with direct patient contact receive vaccine, but we're not so focused on support personnel who don't have direct patient-care contact. I could imagine a scenario with a pandemic where you might want to also include those people because it would be so important that they continue working.
Would there be a similar problems of not being able to produce enough vaccine?
The vaccine that we're testing is intentionally designed to use a process that is as close to the regular flu shot as possible because that is a much easier vaccine to approve by regulatory authorities. They can view that as just being a change in the strains and not a radically new approach to vaccination.
Will the regular flu shot provide any protection against avian flu?
No. But the regular flu shot will protect you against regular flu, and that might actually be more important, at least this year, because no one wants to get regular flu.
What makes this strain of avian flu more virulent than others?
No one knows.
Pandemics happen when a new virus arises that is different in its outer coating from viruses that people have previously been exposed to. When you get the flu, or when you get vaccinated, you make an immune response against the outer coat of the virus. That allows you to be protected against future infections with viruses that have the same kind of outer coat.
Influenza viruses change a little every year. . . . They undergo a process called antigenic drift that does allow them to reinfect people, but those reinfections tend to be much more mild.
Mild, of course, is a relative term. Flu is responsible for deaths and hospitalizations, but [its impact is] ameliorated to a certain extent by the experience -- whether by vaccination or by previous infection -- that a person has had with related flu viruses.
When a pandemic occurs, the central thing that happens is that the virus has a completely different outer coat, and that allows very rapid spread in a population that has no underlying immunity. In 1957 we had a pandemic where a new virus, an H2 virus, showed up in a population that had previously only experienced an H1. And in 1968 we had a pandemic when a new virus, an H3, showed up in a population that had only experienced H1 and H2.
In Asia, many deaths have occurred in young people. Is that due to a lack of previous exposure to flu?
I don't know why that's happening, although my suspicion is that it simply reflects exposure to the birds.
There's been a bit of discussion around the idea of having Roche Pharmaceuticals, the maker of Tamiflu (oseltamivir), either expand and hasten the manufacture of that drug or allow other companies to make it. Would that drug be effective in the face of a pandemic?
Oh, God, I hope so! It and zanamivir, which is a very similar kind of compound, are the only antiviral agents that we currently have that could potentially be effective against the avian flu virus.
As an antiviral, would it only be used for treatment, or could it also be used for prevention?
It would be possible for the avian flu viruses to become resistant. I think the chances are remote, but it is a possibility.
But let's assume for sake of argument that we are talking about a bird flu that is susceptible to these neuraminase inhibitors; we hope and believe that they probably are. Neuraminase inhibitors are clearly very effective when given prophylactically, and I suspect that they would also be very effective in preventing bird flu if taken before exposure. The issue would be whether the supply of the drug would be sufficient to provide preventive drugs to large numbers of people who would have to take this for the entire duration of the time that they were being potentially exposed. You would end up using fewer doses of the drug if you restricted use of the drug to treatment. The issue with any antiviral is whether treatment would be as effective as prophylaxis would be. Here we just don't know.
I haven't been encouraging people to get Tamiflu, and I don't have any myself, but I know a lot of people who do.
Can consumers expect to see a vaccine in the near future?
We have the vaccine that we're testing, which is based on the current bird flu virus that is infecting humans. If we started to see person-to-person transmission with a virus that was the same as that or that was antigenically similar to the virus that we used to make the vaccine, then we would already have some vaccine and it would be a relatively easy matter to make more, although it would take time. If the virus that emerges is antigenically different from the ones that we've been testing, the technology is there to make the seed virus quite quickly, but then it would take the amount of time that it takes to ramp up production [of a vaccine].
Most deaths in Asia have been in people who had direct contact with diseased birds. Should people here avoid contact with birds?
Not right now, because we don't have that strain of bird flu here in North America. But it might come -- in which case, yes.
And so there's no protective benefit to be gained here by, say, avoiding eating chicken?
Actually, I don't think even if we had bird flu here that you would need to avoid eating chicken as long as you were cooking it. I think you wouldn't want to eat raw birds, and you might want to avoid handling live birds, but eating cooked chicken I doubt would cause a risk even if we had bird flu here in the States.
How about being around chickens on, say, a farm or farmer's market?
That is the scenario where you see infections with bird flu in people. And there is no doubt in my mind that if we start seeing bird flu viruses in North America, those markets will have to be closed. ·
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