(May 9, 2006), ABC aired a made-for-TV movie on avian influenza, entitled Fatal Contact. It was not too bad, on the whole, and I am sure it scared the crap out of a lot of people.
The impressions left by Fatal Contact were incorrect or distorted on a number of points:
1. Although a world-wide death toll of 350 million is possible, that is at the outer limits of influenza mortality. It was a worst-case scenario. The most-likely case scenario is much less, even assuming that a human form of the virus will have the same lethality as the existing bird form.
2. The movie assumed that a worldwide pandemic would begin literally within weeks of a mutation, and that it would hit all countries more-or-less simultaneously. Influenza has never behaved that way in all of recorded history. This was an assumption made for dramatic effect, which left a drastically incorrect impression on the viewers.
In reality, we expect that even an extremely lethal human form of avian influenza will behave much like past epidemics. It will move slowly from region to region, giving most of the world many months to prepare.
3. In the movie, the virus actually gained lethality. In the final scene, a new form has appeared in Africa, with 100% mortality. Again, this is contrary to the way viruses evolve. In general, any lethal virus is subject to enormous Darwinian selection in favor of lower mortality, for the simple reason that killing the host is a bad way to survive. For example, the Plague that killed a third of Europe in the Middle Ages is now seldom fatal, and is still visibly losing steam.
In the case of avian influenza, if it ever changes to a human-transmissable form, we can confidently expect it to lose lethality as the months and years progress. Those hit in the first wave will suffer the highest mortality, and each successive wave will be less potent.
4. Speaking of waves, the ebb and flow of the epidemic was very poorly portrayed in the movie. In real life, a community hit by lethal influenza will suffer an initial surge of the disease. Infected people will be isolated in their homes, and after a month or two the initial phase will be over. As people let down their guards, it is entirely possible (even likely) that there will be a second surge of the disease, and then a third. Later waves will be slower and less severe, until finally the average number of newly infected per infectious case drops below 1.0, and the epidemic dies out naturally.
lor
later---
A disease with a short latency period and very high mortality rate is not a good candidate for a pandemic. The key indicator is the average number of newly infected cases per infectious person. That, more than anything, is what drives an epidemic. The faster the disease kills its host, the lower that indicator.
To be really vicious, a disease should have a very long infectious period with no symptoms, followed eventually by a short illness and death -- HIV is an example. THIV has not become pandemic only because it is so hard to transmit, and cannot survive in the open air. Avian influenza, on the other hand, has a latency measured in days and very high mortality. These characteristics serve to reduce the overall predicted severity of the epidemic.
Ebola suffers from the same "problem": it is just too lethal. Local epidemics tend to burn out very quickly.
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