The potential for an avian flu pandemic is something we're constantly asked about at the American Council on Science and Health. It doesn't help that headlines constantly blare about "deadly" outbreaks in Asia and Europe without troubling to clarify whether the outbreaks are deadly to humans or birds. Still, unlike so many health scare stories we analyze, bird flu is not just hype but a real potential threat -- the tricky part is determining how big that potential is.
The major uncertainty is whether the relevant bird flu virus, H5N1, which is already devastating flocks in Asia and Europe, will mutate into a form that has a similar devastating effect on humans. Right now, bird flu can kill humans under rare circumstances (such as when people are in close, frequent contact with raw duck blood, or other conditions highly unusual in developed countries and unusual even in undeveloped ones that increase the odds of transmission from birds to humans). But to devastate human populations in the way that it has bird populations, H5N1 would have to mutate into a form that spreads easily between and among humans rather than just from birds to humans. Currently it does not appear to spread from human to human, and several changes would have to occur in the genetic code of H5N1 for it to do so.
In the meantime, though every death is tragic, bird flu has taken a relatively small toll in human lives. By the end of February 2006, the World Health Organization reported a total of 173 known cases of human infection with H5N1, all among people working in close contact with infected domesticated birds. Of those, 93 had died.
Compared to the daily toll from smoking, car crashes, or countless other killers, those numbers are minuscule -- but there are a few important reasons that we cannot heave a sigh of relief:
--Roughly 54% of those humans who have become infected with H5N1 have died, a disturbingly high fatality rate that may not bode well if the disease begins spreading rapidly among humans.
--The infamous flu pandemic of 1918-1919, which killed tens of millions of people around the world, is believed to have originated as a bird flu -- a reminder that we are especially susceptible to diseases that do not normally occur in mammals and to which we therefore have little immunity.
--It is difficult to prepare in advance for a possible bird flu pandemic because we won't know the exact nature of the virus we're fighting until the dreaded mutations occur that make it easily transmissible between humans.
Despite all these reasons for concern, defensive measures are being taken, including research into new antiviral drugs -- possibly ones that target the parts of the virus's genetic code that are unlikely to alter as it mutates; the development of faster production methods for churning out a vaccine if a pandemic occurs; and the stockpiling of Tamiflu and Relenza, existing antivirals that may help reduce the severity of symptoms for those who catch bid flu, though their likely efficacy is a subject of debate.
While our best hope is that the feared mutations to H5N1 simply never occur, it is wise to be prepared for the small but real possibility, given what history teaches us about the potential magnitude of such a pandemic. At ACSH, we strongly and frequently advise against wasting resources on minimal or purely speculative threats, but this is one case where the consequences might be devastating enough to make a heavy investment now reasonable.
As of the end of February, human cases of bird flu were believed limited to southeast Asia, Turkey, and Iraq. In bird populations, though, the disease had quickly spread to South Korea, Vietnam, Japan, Thailand, Cambodia, Laos, Indonesia, China, Malaysia, Russia, Kazakhstan, Mongolia, Turkey, Romania, Croatia, Ukraine, Iraq, Nigeria, Azerbaijan, Bulgaria, Greece, Italy, Slovenia, Iran, Austria, Germany, Egypt, India, France, Hungary, Bosnia-Herzegovina, Switzerland, Georgia, and Niger.
If it reaches the U.S. -- and in birds, at least, it likely will -- it is likely to appear first on the West Coast, coming over among migratory birds from Asia to Alaska. Again, its appearance in birds alone -- or in very rare bird-to-human cases -- is not reason to panic or even to be surprised. If and when mutations allowing human-to-human transmission occur, it will still not be appropriate to panic -- but it will time to face a potentially devastating crisis with level-headed resolve and the best and most technologically advanced public health resources we can muster.