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Wednesday, October 26, 2005

The bird flu and you

Wth thanks to stratfor.com:

Stratfor subscribers have been sending us a steady river of requests for our opinion on the bird flu situation. Although we are not medical experts, among our sources are those who are. And here is what we have been able to conclude based on their input and our broader analysis of the bird flu threat:

Calm down.

Now let us qualify that: Since December 2003, the H5N1 bird flu virus -- which has caused all the ruckus -- has been responsible for the documented infection of 121 people, 91 of whom caught the virus in Vietnam. In all cases where information on the chain of infection has been confirmed, the virus was transmitted either by repeated close contact with fowl or via the ingestion of insufficiently cooked chicken products. In not a single case has human-to-human communicability been confirmed. So long as that remains the case, there is no bird flu threat to the human population of places such as Vietnam at large, much less the United States.



The Politics of Genetics

An uncomfortable but undeniable fact is that there are a great many people and institutions in this world that have a vested interest in feeding the bird flu scare. Much like the "Y2K" bug that commanded public attention in 1999, bird flu is all you hear about. Comparisons to the 1918 Spanish influenza have produced death toll projections in excess of 360 million, evoking images of chaos in the streets.

One does not qualify for funding -- whether for academic research, medical development or contingency studies -- by postulating about best-case scenarios. The strategy is to show up front how bad things could get, and to scare your targeted benefactors into having you study the problem and manufacture solutions.

This hardly means that these people are evil, greedy or irresponsible (although, in the case of Y2K or when a health threat shuts down agricultural trade for years, one really tends to wonder). It simply means that fear is an effective way to spark interest and action.

Current medical technology lacks the ability to cure -- or even reliably vaccinate against -- highly mutable viral infections; the best available medicines can only treat symptoms -- like Roche's Tamiflu, which is becoming as scarce as the oftentimes legendary red mercury -- or slow a virus' reproduction rate. Is more research needed? Certainly. But are we on the brink of a cataclysmic outbreak? Certainly not.

A bird flu pandemic among the human population is broadly in the same category as a meteor strike. Of course it will happen sooner or later -- and when it does, watch out! But there is no -- absolutely no -- particular reason to fear a global flu pandemic this flu season.

This does not mean the laws of nature have changed since 1918; it simply means there is no way to predict when an animal virus will break into the human population in any particular year -- or even if it will at all. Yes, H5N1 does show a propensity to mutate; and, yes, sooner or later another domesticated animal disease will cross over into the human population (most common human diseases have such origins). But there is no scientifically plausible reason to expect such a crossover to be imminent.

But if you are trying to find something to worry about, you should at least worry about the right thing.

A virus can mutate in any host, and pound for pound, the mutations that are of most interest to humanity are obviously those that occur within a human host. That means that each person who catches H5N1 due to a close encounter of the bird kind in effect becomes a sort of laboratory that could foster a mutation and that could have characteristics that would allow H5N1 to be communicable to other humans. Without such a specific mutation, bird flu is a problem for turkeys, but not for the non-turkey farmers among us.

But we are talking about a grand total of 115 people catching the bug over the course of the past three years. That does not exactly produce great odds for a virus -- no matter how genetically mutable -- to evolve successfully into a human-communicable strain. And bear in mind that the first-ever human case of H5N1 was not in 2003 but in 1997. There is not anything fundamentally new in this year's bird flu scare.

A more likely vector, therefore, would be for H5N1 to leap into a species of animal that bears similarities to human immunology yet lives in quarters close enough to encourage viral spread -- and lacks the capacity to complete detailed questionnaires about family health history.

The most likely candidate is the pig. On many farms, birds and pigs regularly intermingle, allowing for cross-infection, and similar pig-human biology means that pigs serving in the role as mutation incubator are statistically more likely than the odd Vietnamese raw-chicken eater to generate a pandemic virus.

And once the virus mutates into a form that is pig-pig transferable, a human pandemic is only one short mutation away. Put another way, a bird flu pandemic among birds is manageable. A bird flu pandemic among pigs is not, and is nearly guaranteed to become a human pandemic.

Pandemics: Past and Future

What precisely is a pandemic? The short version is that it is an epidemic that is everywhere. Epidemics affect large numbers of people in a relatively contained region. Pandemics are in effect the same, but without the geographic limitations. In 1854 a cholera epidemic struck London. The European settling of the Americas brought disease pandemics to the Native Americans that nearly eliminated them as an ethnic classification.

In 1918 the influenza outbreak spread in two waves. The first hit in March, and was only marginally more dangerous than the flu outbreaks of the previous six years. But in the trenches of war-torn France, the virus mutated into a new, more virulent strain that swept back across the world, ultimately killing anywhere from 20 million to 100 million people. Some one in four Americans became infected -- nearly all in one horrid month in October, and some 550,000 -- about 0.5 percent of the total population -- succumbed. Playing that figure forward to today's population, theoretically 1.6 million Americans would die. Suddenly the fear makes a bit more sense, right?


Wrong.

There are four major differences between the 1918 scenario and any new flu pandemic development:

  • First -- and this one could actually make the death toll higher -- is the virus itself.

    No one knows how lethal H5N1 (or any animal pathogen) would be if it adapted to human hosts. Not knowing that makes it impossible to reliably predict the as-yet-unmutated virus' mortality rate.

    At this point, the mortality rate among infected humans is running right at about 50 percent, but that hardly means that is what it would look like if the virus became human-to-human communicable. Remember, the virus needs to mutate before it is a threat to humanity -- there is no reason to expect it to mutate just once. Also, in general, the more communicable a disease becomes the lower its mortality rate tends to be. A virus -- like all life forms -- has a vested interest in not wiping out its host population.

    One of the features that made the 1918 panic so unnerving is the "W" nature of the mortality curve. For reasons unknown, the virus proved more effective than most at killing people in the prime of their lives -- those in the 15- to 44-year-old age brackets. While there is no reason to expect the next pandemic virus to not have such a feature, similarly there is no reason to expect the next pandemic virus to share that feature.

  • Second, 1918 was not exactly a "typical" year.

    World War I, while coming to a close, was still raging. The war was unique in that it was fought largely in trenches, among the least sanitary of human habitats. Soldiers not only faced degrading health from their "quarters" in wartime, but even when they were not fighting at the front they were living in barracks. Such conditions ensured that they were: a) not in the best of health, and b) constantly exposed to whatever airborne diseases afflicted the rest of their unit.

    As such, the military circumstances and style of the war ensured that soldiers were not only extraordinarily susceptible to catching the flu, but also extraordinarily susceptible to dying of it. Over half of U.S. war dead in World War I -- some 65,000 men -- were the result not of combat but of the flu pandemic.

    And it should be no surprise that in 1918, circulation of military personnel was the leading vector for infecting civilian populations the world over. Nevertheless, while the United States is obviously involved in a war in 2005, it is not involved in anything close to trench warfare, and the total percentage of the U.S. population involved in Iraq and Afghanistan -- 0.005 percent -- is middling compared to the 2.0 percent involvement in World War I.

  • Third, health and nutrition levels have radically changed in the past 87 years. Though fears of obesity and insufficient school lunch nutrition are all the rage in the media, no one would seriously postulate that overall American health today is in worse shape than it was in 1918. The healthier a person is going into a sickness, the better his or her chances are of emerging from it. Sometimes it really is just that simple.

    Indeed, a huge consideration in any modern-day pandemic is availability of and access to medical care. Poorer people tend to live in closer quarters and are more likely to have occupations (military, services, construction, etc.) in which they regularly encounter large numbers of people. According to a 1931 study of the 1918 flu pandemic by the U.S. Public Health Service, the poor were about 20 percent to 30 percent more likely to contract the flu, and overall mortality rates of the "well-to-do" were less than half that of the "poor" and "very poor."

  • But the fourth factor, which will pull some of the strength out of any new pandemic, is even more basic than starting health: antibiotics. The 1918 pandemic virus was similar to the more standard influenza virus in that the majority of those who perished died not from the primary attack of the flu but from secondary infections -- typically bacteria or fungal -- that triggered pneumonia. While antibiotics are hardly a silver bullet and they are useless against viruses, they raise the simple possibility of treatment for bacterial or fungal illnesses. Penicillin -- the first commercialized antibiotic -- was not discovered until 1929, 11 years too late to help when panic gripped the world in 1918.



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    Posted on 10/26/2005 06:28:00 AM Backlinks


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