There have been many warnings of late that if A(H5N1), the avian flu strain spreading in Asian bird populations, were to mutate into a form easily transmitted between humans, a pandemic might result on the scale of the 1918-1919 flu that killed tens of millions of people.
There are three main reasons not to panic just yet, one epidemiological and two pharmaceutical: the low number of deaths so far, the announcement this past weekend of an effective vaccine against bird flu, and -- if it is produced in sufficient quantities -- the antiviral drug Tamiflu for treating those who do catch bird flu.
Planning ahead is a good thing, so it's reassuring that public health officials now routinely keep an eye on potential outbreaks and take preventive action (witness incidents such as the quarantining of a passenger plane on a Boston runway in 2000, when it appeared one passenger, who was bleeding from the eyes, might have the deadly, organ-liquefying ebola virus -- but turned out to have a bad case of conjunctivitis). It's good, too, to be aware of worst-case scenarios such as the 1918 pandemic -- which was as devastating as the World War with which it coincided -- but preparation is possible without needless anxiety.
If We Knew Then
It's important to remember how different the world was in 1918 and why we're in better shape to cope with a flu outbreak today. For starters, scientists did not even know that the flu was caused by a virus back in 1918. Today, we not only know it's a virus but know the genetic codes of various flu strains so well that we can predict what sorts of mutations in avian flu would be likely to make it more efficiently transmissible between humans. We have also reconstructed the likely genetic code of the strain responsible for the 1918 pandemic and studied the implications for plague control of its likely man-to-pigs-to-man pattern of transmission.
For good or ill, humanity is also a good deal more adept at crowd control and curfew enforcement than it was in 1918. Then, paradoxically, a populace accustomed to outbreaks of cholera and yellow fever was not as easily driven indoors and away from mass gatherings by word of a new plague as today's citizens, accustomed to near-constant good health, likely would be.
The Toll Thus Far
With all that in mind, we should take some comfort from the World Health Organization's (WHO's) continually-updated figures for human cases of and human deaths from bird flu worldwide. As of August 5, the numbers stood at 112 and 57, respectively. (For purposes of comparison, note that the average number of deaths per year from the conventional flu in the U.S. is 36,000, a fairly large number that causes fairly little panic.) Fifty-seven dead is a far cry from the estimated 25-50 million killed in the 1918 pandemic -- though, of course, the idea is to nip potential future pandemics in the bud. Of the bird flu deaths so far, only one is thought with some confidence to be a case of human-to-human transmission, and that was extraordinary (and tragic): a mother who reportedly held her dying child in her arms for five days before becoming infected herself. The mutation of the virus into a form easily transmissible between humans thus far remains just a scary hypothetical.
So far, it appears that avoiding the consumption or handling of infected birds has been sufficient to prevent a human outbreak (some 140 million chickens have been killed in Southeast Asia to minimize the risk), and reports of the flu spreading among birds in Russia and Central Asia should not be treated as synonymous with a spreading, imminent threat to humans. All but 17 of the reported human deaths so far have occurred in Viet Nam, nearly all the rest in Thailand, and there is still reason to hope human cases will largely be contained in these areas.
Nonetheless, it was welcome news this weekend that a study conducted by the National Institute of Allergy and Infectious Diseases (NIAID) reveals the efficacy of a vaccine against avian flu. Study head Dr. Anthony S. Fauci said that 113 of the 452 test subjects participating in the study had already shown a protective immune response to the vaccine and that he was confident the other test subjects would show similar results. Officials are divided on whether to begin vaccination now or await signs of an outbreak. The World Health Organization would likely leave the decision to member countries -- and in the U.S., the usual FDA-approval red tape could be avoided by declaring the vaccine a variation on an old, already-approved product rather than a new one.
Rather than inoculating the entire population of the planet, the preferred strategy for coping with plagues, given limited amounts of vaccine, is to inoculate people at high risk either before or during the outbreak, thus limiting the disease's spread. The U.S. government is currently requesting enough of the vaccine from French company Sanofi-Pasteur to inoculate some 4.5 million people, though the number of people who could be protected will depend in part on what dose of the vaccine scientists conclude is optimal. It so far appears that the best results for the anti-avian flu vaccine come from a higher-than-expected 90-microgram dose, in two big shots.
That makes it all the more reasonable to pursue a back-up strategy of producing a drug that can treat the disease once people contract it.
Tamiflu Isn't Just for Coughing and Sneezing
As recently as two months ago, before the vaccine announcement, Fauci and others at NIAID had emphasized another element of our defense against avian flu as a top priority: the construction within the United States, with the cooperation of the government, of a plant for the production of Tamiflu (oseltamivir), an antiviral drug originally created to combat conventional flu strains by preventing the virus leaving the host's cells once inside them, limiting the disease's spread. The biotech company Gilead, which created Tamiflu, is currently in a legal battle with the Swiss pharmaceutical company Roche, with which it had contracted to manufacture and distribute the drug, complaining that Roche hadn't done enough to distribute and popularize Tamiflu and was jeopardizing public health.
But Tamiflu became a much hotter commodity -- giving Gilead additional reason to demand the rights to the drug back from Roche and to request that their legal dispute be settled within eighteen months -- when tests recently revealed that Tamiflu is one of the few drugs capable of suppressing avian flu in lab mice. Scientists think it is likely the drug would have a similar effect in humans.
With luck, neither legal disputes nor regulatory hurdles will slow production, since drugs capable of fighting avian flu -- especially if the virus continues to mutate -- easily become obsolete. Take the case of the drug Amantadine, for which scientists at one point had high hopes as a principle weapon in treating avian flu. That was before the revelation that China had been illegally administering Amantadine to poultry, hoping to save millions of the valuable birds from slaughter -- but in the process gradually creating avian flu viruses immune to the drug. The WHO had been expecting to use Amantadine in humans around the world in the event of a human epidemic, but it would now likely be useless in many regions. There is still time to handle Tamiflu production, distribution, and use more wisely.
Dark If's and Reason for Hope
Talk of a human pandemic of bird flu is not unreasonable, but our very awareness of the conditions necessary for a pandemic make it unlikely we will easily fall prey to one again. Most of the worst-case scenario talk about avian flu relies upon a string of as yet unrealized and pessimistic if's: if we do nothing to decrease contact with infected animals, if the virus mutates into a form easily transmissible between humans, if no vaccine is in place to contain outbreaks, if no drugs are available to treat victims, then we might face death on a scale similar to that seen in 1918. But we're smarter than that. We're wiser and more experienced now, and when we choose to, we can make technology and mass production move even faster than the viruses.