Frank,

You have to take what you hear in the media about West Nile Virus, SARS,
avian flu, &c. with more than a few grains of salt. In my view, the media
covering these, and other, diseases are guilty of creating substantial
terror by not putting the risks due to these diseases into context. And
they're worse than the terrorists from the muslim world because the fear the
media created of these diseases is wholly unwarranted.

In the case of West Nile virus, it does not move directly from human to
human, regardless of how close or intimate the contact. It only moves via
direct exchange of blood. Of all the mosquito species there are, and I
can't tell you off hand how many species there are, there are in fact only a
handful that bite people. The only species directly implicated in the
transmission of West Nile virus has very restricted habitat requirements.
It requires very small, sheltered bodies of water, such as would occur in
blocked eaves troughs, bird baths surrounded by a tall hedge, discarded
tires, &c. And Ray is right: they'd have to have direct access to the
surface of the water. Even a simple screen is enough to make, say, the
water in a rain barrel, inaccessable. One thing to bear in mind, generally,
about mosquitoes, is that they are very weak swimmers and fliers; the
slightest breeze or current is enough to make a given location unsuitable as
their habitat. While it can be found here in southern Ontario, it does not
occur in any of the many wetlands surrounding Orillia (where I live).
Furthermore, it generally travels no more than a few hundred metres from
where it emerged from the water as an adult. Therefore, if you and your
immediate neighbors are diligent in cleaning out your eaves, replacing bird
bath water every few days, etc., you will have collectively ensured that
there is no viable habitat for it.

But your risk is small, even if you do nothing. You have to have a
significant number of people (or birds) infected by the virus in order for
there to be an estimable risk of becoming infected, and even if you do get
infected, the probability is that you won't even show symptoms. The
probability of disease due to this virus is the lowest of any for which I
have seen data, and the vast majority of those infected who do display some
symptoms, suffer a disease much milder than the common cold. While there is
a measurable risk of serious disease (serious enough to produce long term
debilitating consequences), it is extremely low: too low, in my opinion, to
worry about. It is much more sensible to fear the common influenza virus
than it is to fear any of the diseases we have heard so much about in the
news recently; and no-one, apart from the elderly, extremely ill, and
parents of very small children (worried about their children rather than
themselves), has cause to fear the flu.

The best way to address your fears about West Nile virus, is, rather than
taking all kinds of precautions which will cost money, to obtain reliable
information. Do a search on the web to find out, first, which mosquito
species are vectors for it, second, the probability of displaying symptoms
once infected, and then the probability of requiring hospitalization once
symptoms are apparent. And to put the risks into perspective, do an
additional search to assess the risks associated with influenza, SARS,
ebola. Ebola is an especially interesting case because, while very deadly,
it is also so rare and difficult to transmit from one person to another,
there have been fewer cases of it over the past few decades than even SARS
in the last year alone.

Note, while I say there is no need to fear, I am not saying it is wise not
to consider normal prudence. The fact is that if there is sufficient data
for us to estimate the probability of a given event (e.g. that a person will
become sick due to West Nile virus), then that event is not only possible,
but certain. But the certainty that someone will get sick with West Nile,
or die from SARS, does not mean that it is likely that you will suffer
either fate. All it means is that one would be wise to cooperate with
initiatives from public health authorities in their efforts to prevent a
public health crisis. If the authorities learn of a new disease, it is
their responsibility to initiate prudent measures, assuming the worst case
scenario, until such a time as there is good evidence to allow a good
evaluation of the releant risks (and at the same time, they need to be
subject to public scrutiny to ensure they are effective in balancing the
relevant costs and risks). In my estimationg, both they and the nedia have
stumbled badly WRT all these diseases, as well as the recent cases of BSE.

Anyway, this isn't the forum for a detailed treatment of risk analysis and
public health. I just wrote what I did to enable you to effectively deal
with your fears as they impinge on how you deal with your orchids.

Cheers,

Ted


"Frank H. Kirchner" wrote in message
news:wIZTb.2185$Yj.680@lakeread02...
Hi guys-

I am very happily converting a large share of my orchid collection to
semi-hydroponics. The plants are happy. I am happy. So, as I lust for
the warmth of summer, I started worrying. I have one hell of a lot of
standing water in my pots now and started worrying about mosquitoes. The
concern is a bit more than worrying about a pest as the West Nile Virus is
increasingly prevalent here in Virginia. Will regular watering and
flushing
being adequate to remove mosquito larva? Will a couple of drops of bleach
damage orchids? What thoughts do you growers have about controlling
mosquitoes in your greenhouse/collection?

Will summer come soon? I'm desparate!

Thanks all.

Frank

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