Alien diseases: The War of the Worlds redux
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When considering issues of space travel and exobiology (life originating beyond the earth), the question often arises of the dangers of infection of alien biologies by earth organisms or earth biologies by alien organisms, should they come into contact.
The issue here is not ecological contamination (on which I'm silent for the moment), but the internal infection of living beings by other “disease-causing” organisms.
In my considered view, the danger of infectious agents “jumping” into creatures of fundamentally different evolutionary origin (whether going in either direction) has been considerably overrated.
Most diseases that we see here on Earth are closely attuned to the life cycle and other intimate aspects of the specific organism they infect.
Pathogens which can transmit much beyond a single species across a broader related group (e.g., rabies) are few; while diseases more typically almost have to be coaxed into jumping from one species into even a closely related one.
The reason is clear: creatures' cells and their immune systems fight like hell against being taken over, and the alien environments of non-adapted-to species (much less the really alien environments of a never seen before, wholly different evolution) are just too difficult for even opportunistic agents to endure, much less triumph.
The probability an Earth organism could infect a creature from a totally different evolutionary origin is thus remote (i.e., the Martians should have won ”The War of the Worlds”).
The converse (alien diseases infecting earthlings) is also quite unlikely — except, that is, in the case of an intelligently designed disease-causing agent (a la Harry Harrison's A Plague from Space), using technology basically beyond what we have even today, but which might well then be unstoppable.
After hearing me say that (on a mailing list discussing alternative futures and pasts of
Harry Turtledove's
books), a correspondent wrote back:
But I've heard speculation about mankind facing possibility of infection while exploring space; and the first astronauts endured severe quarantine procedures.
Yes (I replied), people worry about it, and I'm not going to say that precautions aren't in order (just as we might want to take precautions against asteroidal impacts), but the overall probability of running into trouble as a result of (naturally evolved) alien diseases appears quite low.
(Fortunately, as the first astronauts' quarantine procedures weren't really all that good.)
Labels: disease, extraterrestrial life
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