Friday, June 03, 2005

H5N1 in Qinghai revisited

I was asked to clarify my position with regards to the Qinghai H5N1 outbreak.

In general, I try to view new information as a skeptic. When I question the evidence for a statement or conclusion, it doesn't necessarily mean I don't agree with the conclusion. I just think it is important to not sensationalize or draw premature conclusions on unverified evidence. I would rather dismiss something I agreed with on the grounds that the evidence was insufficient, than use incorrect information to in error support a position I believed in.

I do think that if a highly pathogenic influenza pandemic occurs, it could be the most significant public health crisis since HIV/AIDS. Millions could die, many more could get sick, and the economic fallout could be catastrophic. We need to be prepared, and dilligent in watching for signs that it is occuring. In 1918, without the massive air transportation system we have today, it took only 6-8 months for H1N1 to sweep the globe. Today, one can get from anywhere to anywhere in a frighteningly short amount of time.

That been said, my positions on the Qinghai outbreak are these:

- Although H5N1 has been isolated at Qinghai Nature Preserve, information on the cause of death in the reported dead wild birds is unavailable. Avian influenza commonly circulates in wild birds, and although H5N1 has rarely been isolated from wild birds, it is possible that the virus was incidental to other causes of death. I had a flu earlier this year. If I was hit by a bus, and the pathologist did a swab and was able to isolate the virus, she would not conclude the flu killed me (the bus did). As we hear again and again, a mortality event of this magnitude would be unprecedented if it was caused by H5N1. We should be skeptical of claims that influenza killed these birds without good evidence.

- If it can be shown a significant number of birds did die of H5N1 at Qinghai, then my level of concern would go up. However, this makes the issue a conservation issue, not necessarily a human health issue. Because H5N1 has rarely been isolated from wild birds, the simplest explanation is that the presence of H5N1 is the result of a migratory bird picking up the virus in southeast Asia from an affected domestic poultry farm. Pathogenic avian influenza then could result in increased mortality in wild birds, thus provide an increased threat to species that are already at low density. This illustrates the global trend of livestock diseases affecting wildlife, and causing population declines. We need to recognize that human, livestock and wildlife health are one and the same.

- There is fear that migratory birds could potentially spread H5N1 into new areas. Species that die of H5N1 are unlikely to spread the virus, but of course there is the potential that those species that can carry the virus without getting ill could spread the disease into previously unaffected areas. This brings up the issue of biosecurity. The best way to prevent diseases from going from domestic poultry into wild birds (spillover) and then going back into domestic poultry from wild birds (spillback) is through improved biosecurity. Essentially, contact between domestic poultry and wild birds should be minimized and prevented as much as possible. This protects both domestic and wild birds from a number of diseases, not just avian influenza. Many government agencies will be tempted to cull wild birds in order to “contain” the epizootic – we know this won't work.

- We should be hyper vigilant for human cases of avian influenza. The final impediment stopping the epidemic is human to human transmission. At the first demonstrable sign that avian influenza has acquired the ability to transmit easily among humans, drastic measures should be taken to prevent its global spread. I recognize that there are a few documented cases of human to human transmission already, but so far it seems to be limited.

Governments worldwide are unprepared for the next avian influenza pandemic. As practitioners of wildlife, livestock, and human health, we all have a responsibility to promote policies that will reduce or ameliorate the impact of the next pandemic. However, this cause is not served by being sensational, or by invoking chicken little. We must be cautious in our assessment of “facts” so that when we do raise the alarm, it is credible and receives the attention it deserves among policy makers.


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