"A Question Of When, Not If"

by Andrew Lam

(PNS) -- The bird flu virus, H5N1, has the potential to kill millions once it learns how to jump from human to human. So far, most people who become infected have worked with live chickens. But scientists say it's a matter of time before bird flu makes the leap. The virus most recently surfaced in Indonesia, where four people have died. PNS and New California Media (NCM) editor Andrew Lam spoke with Dr. David Relman, professor of medicine and of microbiology and immunology at Stanford University.

NCM: Should we ask if bird flu will jump from animal-to-human transmission to human-to-human transmission -- or is it a question of when?

DR: It probably is a question of when, not if. This virus is progressing right down the path you would predict for a virus that will eventually become quite good at human-to-human transmission.

NCM: Is there a timeline?

DR: That's the hard thing. Some people say it could be as early as this winter. Those of a more optimistic sort say maybe two years, or five. I think the really important question is, when it acquires that capability (human-to-human transmission), what will it cost the virus? Most people think it won't be as virulent.

NCM: Since the number of people who have died so far is small, can we really speculate about the number of fatalities bird flu could cause?

DR: Right now, of the known cases of bird flu in humans, it has killed about 50 percent. The big question is, are there others out there walking the streets, sitting in their homes, eating dinner and talking to their family members who have become infected and didn't even become sick? I don't think there are many. There are some surveys out there of blood from people who are healthy to see if they have evidence of exposure to this virus, and there haven't been many episodes or incidences of that. But it's still possible.

NCM: How will it be transmitted among humans? I imagine if it is airborne, like SARS, it is going to be very contagious.

DR: Correct. It almost certainly will behave just like all the influenza viruses before it, meaning that it will be aerosol-transmitted. In fact, the current human-to-human flu viruses that we all experience each winter are more transmissible than SARS. They actually become transmitted easily through fine-particle aerosols, person to person. SARS required large droplets or even direct contact.

NCM: I was traveling in Asia near the beginning and at the end of the SARS epidemic, and the attitude regarding SARS, especially in big cities, was one of sheer panic. Yet with bird flu the attitude is 180 degrees different. In Hanoi friends said to me, "Oh, it's just farmers who get it, so just don't eat chicken now and you'll be OK."

DR: It probably reflects something about human nature. At the time you're talking about, during the height of the SARS event, there were a lot of people who were sick. There were hospitals that were shut down. There was already a fairly substantial impact on the health care system in a few major world cities.

We're not there yet with bird flu. I think the inevitable course will be that this virus will become better at human-to-human transmission, and when it does that, SARS unfortunately may look like quite a small little blip.

NCM: What about the new vaccine being developed against bird flu?

DR: The vaccine does appear to induce what should be protective immunity in humans. That's the good news. The bad news is that even with the prototype vaccine in hand, we still don't have the production infrastructure to make enough doses quickly. If every vaccine producing factory in the world were devoted solely to the purpose of making this new influenza vaccine, at current levels of production we would only have enough for maybe 50 to 100 million doses worldwide, for a whole population that needs 10 times more doses.

NCM: Why do you think the last few diseases of concern -- SARS, bird flu and now swine flu -- all seem to originate from one particular area, either Southeast Asia or South China?

DR: For reasons that are still unclear, influenza, even yearly, seems to evolve out of the bird population of Southeast Asia. Nobody knows why. SARS seems to also have found a natural home in animal populations of China, and then moved into humans when those animals were moved about. But every continent has its sites for the origin of a new emerging infection.

NCM: But are there common conditions that promote the development and spread of such viruses?

DR: Where you see emerging infections around the globe, you see dislocations of animals, you see disease in animals because of crowding, you see displacements of humans, crowding of humans, poor sanitary conditions, poor hygiene, war, famine -- anything that perturbs what might have previously been a fine-tuned balance in nature.

NCM: Has our changing relationship with animals encouraged the rise of new diseases?

DR: There have been major changes in the way we manage animal populations. One of the most important in the more developed world is the rise of very large-scale, industrial scale livestock management, farming that involves populations of hundreds of thousands of millions of animals all packed together. It's easy to see where an infectious agent might have lived and died within a small population of animals, but now has the opportunity to move within millions very easily.

We also move animals about the globe in ways that we never ever did ten, 20 years ago. Look at monkey pox, which showed up in the United States two years ago. How did it get here? We are importing millions of exotic strains and species of animals that have no place being in North America, due to Americans' desires for exotic and unusual pets.

NCM: So basically the rise of new diseases, or a lot of them anyway, are the direct cause of our human behavior?

DR: Correct. We are at fault in many ways.

NCM: But with technology we are also quicker in defining and isolating the cause of diseases.

DR: Yes, you have to hope that on the one hand, while we're the cause of many of our own problems, we are also the potential solution.