Bird flu is a disease caused by a specific type of avian (bird) influenza virus, the so-called H5N1 virus. This virus was first discovered in birds in China in 1997 and since then has infected 125 people in Vietnam, Cambodia, Thailand, and Indonesia, killing 64 of them. It is spread by infected migratory birds (including wild ducks and geese) to domestic poultry (primarily chickens, ducks, and turkeys), and then to humans.
Since 1997, and especially since the beginning of 2004, approximately 150 million birds have either died from the disease or been killed to prevent further spread. Nevertheless, this very infectious and deadly virus has spread relentlessly to China, Thailand, Cambodia, Vietnam, South Korea, Japan, Taiwan, Laos, Russia, Indonesia, Mongolia, Kazakhstan, Malaysia, Turkey, Romania, England, Croatia, Macedonia, and other countries. This ongoing geographic extension of the virus is of great concern around the world. It is feared that it will continue to spread to all continents, including the Western Hemisphere—and it no doubt will.
Normally, different types of viruses infect just one, or a limited number, of species specific to the particular virus type. The bird-flu virus, however, has infected a large number of birds and animals, including ducks, chickens, turkeys, tree sparrows, peregrine falcons, great black-headed gulls, brown-headed gulls, gray herons, Canada geese, bar-headed geese, little egrets, pigs, clouded leopards, white tigers, mice, domestic cats, crows, magpies, peacocks, blue pheasants, rare eagles, turtledoves, swans, terns, and others. This is another sign of the virulence or destructiveness of the virus.
Researchers, historians, and infectious-disease experts have determined that influenza pandemics (global epidemics) occur approximately once every 30 years. The most deadly pandemic ever recorded occurred in 1918-19, killing more than 100 million people across the globe in less than two years. Two other much less severe pandemics occurred, one in 1957, when approximately two million people died, and one in 1968, when about one million people died. Because we have already had three pandemics in less than 100 years, we are “overdue” for another one. Enter SARS-CoV-2 coronavirus in 2020, killing so far only 325,810.
And so this disease-causing virus continues to infect more and more species in more and more countries. In laboratory experiments, it has been shown to be one of the most lethal influenza viruses ever known. In addition, just recently and after 10 years of work, researchers determined that the H5N1 bird-flu virus is genetically more similar to the deadly 1918-19 influenza pandemic virus than to the viruses which caused the much less severe pandemics of 1957-58 and 1968-69.
To summarize the important points so far:
- The bird-flu virus is a very deadly strain of avian influenza called H5N1 that has killed millions of birds;
- the virus is spreading relentlessly around the world;
- the virus has infected many species, which is uncharacteristic of most viruses;
- the virus has been shown to be similar to the most deadly virus ever known, which caused the 1918-19 pandemic;
- the virus has been shown to be much more deadly in laboratory experiments than regular influenza viruses; and
- the virus is known to have infected at least 125 humans and killed 64 of them so far, yielding a fatality rate of approximately 50 percent.
The virus continues to kill humans, but at a slow rate—it has not yet acquired the capacity to be easily transmissible between humans; humans become infected primarily from sick birds. Because humans alive today have no natural immunity to the H5N1 virus, once it becomes easily transmissible between humans a pandemic or global epidemic will occur. The central question is, when will it exchange enough genetic material with the usual seasonal human influenza-viruses to become more like a human-influenza virus—and thus become easily transmissible between people?
Many people believe that the virus will continue to spread around the world until it is present in most or all countries—before it will “go human” (become easily transmissible between people). And that may be the case. The pandemic of 1918-19 is thought to have started in Kansas (of all places). So it is certainly possible that the coming pandemic could start somewhere else than in Asia—although most experts believe it will, in fact, start there. It could start in a country which has not yet been host to the virus.
However, it is most certainly not necessary for the virus to march all the way around the world before a pandemic can begin. The fact that the virus already has spread to more than 15 countries, and to many different bird and animal species, provides the opportunity for it to commingle with a human-influenza virus and create the dreaded human contagion. There is no known reason why this could not happen tomorrow. While it is true that the probability of the switch increases with time, the probability of its happening tomorrow is far from zero.
The flip side to the possibility that the crossover could happen at any time is the fact that the virus has been around at least since 1997 and, as a matter of record, has not yet switched to a deadly human-to-human form. At least a few scientists believe that the virus can’t and won’t make the switch to a deadly form, possibly ever.
And so we are left with these two very different possibilities—at any time, and as soon as tomorrow, the virus could mutate into a deadly form, readily transmissible between people—or it might never transform itself into such a form. There appears to be much more evidence for the former and, presumably, that is why the vast majority of scientists and governments are scrambling to prepare for the worst.
This situation is analogous to living on the Gulf Coast during the beginning of hurricane season. Residents there have been through it before, but most of the time the storms are not too severe and the people can get by without too much hassle. However, there have been rare severe storms that have been devastating. Some day another hurricane is coming, and it appears that it might well be a Category IV or even V by the time it strikes land. However, that’s not certain—no one can say for sure, and no one knows exactly when it will strike land. So what should the residents do? What should the residents have done before hurricane Katrina?
The coming bird-flu pandemic might be mild and it might not come for years. On the other hand, it might be severe and it might start tomorrow. The U.S. Government Accountability Office (GAO) has said, “While the severity of the next pandemic cannot be predicted, modeling studies suggest that its effect in the United States could be severe.” We should also be mindful that the pandemic could come at any time, even before the virus methodically marches around the globe. No matter how advanced science has become, we still can not predict when the switch will occur; it is currently unknowable—and that does not mean it will come later, in a predictable fashion. As Miguel de Cervantes admonished, “Forewarned, forearmed.”
Due to the high lethality and virulence of H5N1, its endemic presence, its increasingly large host reservoir, and its significant ongoing mutations, in 2006, the H5N1 virus has been regarded to be the world’s largest pandemic threat, and billions of dollars are being spent researching H5N1 and preparing for a potential influenza pandemic. At least 12 companies and 17 governments are developing prepandemic influenza vaccines in 28 different clinical trials that, if successful, could turn a deadly pandemic infection into a nondeadly one.
Article written by Bradford Frank, M.D., M.P.H., M.B.A.