The scary thing is that at least one strain (the Ebola Reston strain (see Ebola-like Reston virus in Monkeys, paragraph 2; Haemorrhagic Fevers: Ebola; Ebola Haemorrhagic Fever Fact Sheet, section "History and Prevalence"), which was written about in "The Hot Zone" and vaguely alluded to in "Outbreak") can be transmitted through the air. This is the strain that broke out in the USA in 1989, by the way.
Fortunately, the Reston strain differs enough from the other varieties in that it does not apparently cause any symptoms in humans. Still, it's scary to think that such a close cousin of this particular virus can spread through the air - or, for that matter, that such a particularly nasty beast even exists.
The strange thing is, though, that Ebola outbreaks increased in virulence as time progressed (I forget where I read this, so do not take the following as the gospel truth - it's simply my own error-prone memory). If I recall correctly, a related outbreak in Marburg, Germany (sometime around 1960) had a fatality rate of less than 50%; subsequent outbreaks in the mid-70s in Sudan and Zaire had mortality rates around 50%; later outbreaks, particularly of the Zaire strand, had mortality rates approaching 90(+)%. (oh, wait - here's an article with some relevance: Institute for Molecular Virology: Marburg and Ebola Viruses, section "History")
This is downright wierd. Haemorrhagic fevers kill so quickly that they can burn themselves out - they break out in a terrifying, spectacular fashion, kill a huge number of people and then die out, because not enough hosts survive to continue the outbreak. This is bad for the virus itself from a survival point of view - how can it spread and evolve if its hosts are all dead? It doesn't make any sense.
Anyhow, it's been a while since I've done any reading about ebola and its cousins - might be time to catch up on what's been happening in the past five or so years.
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