Did Al Qaeda bring over the West Nile Virus as a form of bilogical warfare?
I doubt it. Likely candidates are the illegal bird trade (infected birds where the virus recrudesces under stress, my vote), cargo with infected adult mosquitoes (quite possible), cargo with infected mosquito larvae (less likely as transovarial transmission is rare), infected humans (not likely since humans are a dead-end source, with dead-end meaning we do not make enough virus to maintain an arboviral cycle) and infected legally imported bird species.
West Nile is the most widely-spread Flavivirus. Given the amount of material (organisms and cargo) that is transported around the world everyday, it’s not surprising that it became an emerging disease in the Western Hemisphere.
Not to mention that it’s not exactly causing widespread panic or harm to the U.S.
The virus is spread primarily through mosquito bites and even if you’re bitten by an infected mosquito your chance of infection is slight. As far as biological warfare goes West Nile is not an option that would be considered effective.
Also Al Qaeda seems to have a propensity for making a large splash/statement with their attacks and something as subtle as the spread of a disease that an individual has a good chance of surviving even if they do catch it doesn’t fit with that modus operandi.
“Likely candidates are the illegal bird trade (infected birds where the virus recrudesces under stress, my vote)…and infected legally imported bird species.”
There seem to me to be some real problems with the captive bird theories that are so popular with the media. Many captive birds are high value birds that are kept indoors, especially in northern North America. And aren’t those that are imported legally quarantined for at least 30 days indoors at one of a half dozen USDA port of entry facilities? As for illegally imported birds, they aren’t quarantined but, being valuable and contraband, aren’t they likely to be kept out of sight indoors?
Another possibilty is carriage by a one of the hundreds or thousands of birds that make it each year from Europe/Africa to the Americas.
I don’t think the legal bird trade is that much of a candidate (although a slight possibility) for much of the reason you mentioned: the birds are quarantined and examined for disease. Prior to 1999, I don’t know if West Nile was one of the diseases screened and if it was, which techniques are used (virus or antibody detection). But this has been one of the possibile introduction mechanisms considered.
As far as the illegal bird trade is concerned, I think the type of trade varies quite a bit. Some might bring in a few expensive birds, taking care to isolate the birds from each other and taking good care of them. Others may work in the “puppy mill” mentality, going for quantity rather than quality. If you had a lot of birds, you might keep them in aviaries, thus exposing them to mosquitoes.
You’re right in including birds that come over naturally (storm-blown, for example). But the reasons why I think that’s a less likely scenario are these: Introductions of organisms (disease) seem to require a certain level, a certain “viral load” to take hold in naive areas. Which mechanism is likely to deliver that load to the NY area? Birds coming over naturally would most likely come over the same way Cattle Egrets came over - through prevailing winds and well to the south (South America). There is no evidence that West Nile broke out anywhere else than the NY area. Which birds are the most likely to act as a reservoir? The number one reservoir in the Old World is the House Sparrow. This is an awfully small bird to successfully make its way to the NY area without human help. Finally, the virus (in 1999) was determined to be genetically identical with that involved in an Israeli outbreak of the previous year. Whatever brought the virus here came from that area first.
It’s certainly a possibility that the virus was introduced naturally (and I’ve been wrong about a number of things with West Nile :)). I don’t know if we’ll ever find out how it arrived. I do know that I gotta go bleed crows right now and I apologize for any incoherency. 