Fran,
This one would be medically and physiologically impossible. The virus could not survive long enough to make it through the mail, even if it was attached to the envelope's gummed closure flap. Virus' are fairly fragile, especially when it comes to temperature extremes, and the vast majority die in a matter of minutes after being exposed to a dry, cold environment. However, they can be easily transmitted via human mucosa, and primarily are passed from one person to another when the carrier coughs or sneezes. One more reason not to let someone else use your mic.
Cheers,
Gary
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Travlin' Easy
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K+E=W (Knowledge Plus Experience = Wisdom.)