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  • From: list@ginda.us
  • To: North American Fruit Explorers <nafex@lists.ibiblio.org>
  • Subject: West Nile, was: [NAFEX] The bird pressure
  • Date: Mon, 5 Jul 2004 07:52:28 -0400


On Jul 2, 2004, at 9:45 PM, Dylan Ford wrote:
. . .I enclose here material regarding West Nile Virus lifted in part and without
permission from a Red Cross web site.

. . .
There is no
specific treatment for WNV infection or vaccine to prevent it.
. . .
No cases of West Nile Virus attributed to transfusion of blood or blood
products have been reported either in the US or in other areas of the world
with previous epidemics. While there is a theoretical possibility that WNV
can be transmitted by blood transfusion the risk is regarded as extremely
low. In areas where there are human cases, the low theoretical risk is
further reduced by careful attention to existing donor screening procedures.


I think this information was out of date in two places. (And I note that it listed the number of people to catch the disease in the US only up through 2002.)

First, there is an effective vaccine, but it has only been approved for horses. West Nile is a more serious problem for horses than for people (a much larger percent become infected when exposed, and a larger fraction of those go on to become seriously ill) and the vaccine manufacturers saw a solid market among thoroughbred breeders. Also, it's much cheaper to develop a horse vaccine than a human vaccine. You can intentionally expose cheap animals to the virus to test possible vaccines, and if there is some long-term or rare problem that shows up after the vaccine is marketed, your maximum liability is the cost of the horse. Second, I'm pretty sure there has been one documented case of West Nile spreading either through a transfusion or a transplant - I forget which.

There's a reason beyond cost that there isn't a human vaccine. It's a really rare human disease - even in areas with very high levels of virus (such as where I live, judging by the crows) people almost never catch it. It's like equine encephalitis, St. Louis encephalitis, and a whole host of rare bug-born diseases that we've had for years - bad news if you catch it, but not a major public health threat. Personally, I'm much more scared that malaria might make a comeback in the temperate climes than I am of West Nile. I'd rather we not have it, of course. (In part because I really like crows, and in part because of the human risk) but "not having it" is no longer an option, and I don't think we need to do extraordinary things to avoid it. Besides, odds are your neighborhood will be infected whether or not your neighbors put out bread for the birds.

Ginda





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