Cynthia:

My understanding is that this bug can't be contracted by the sort of  casual exposure in a supermarket that you suggest.  The problem with being on a plane is that the air is recirculated, so the exposure to an airborne bug is focussed.  And the longer the flight the more focussed the exposure.  I'm thinking about going to Key West for vacation, but might just drive rather than fly.  Although, to tell the truth, with the price of gasoline I might just take the risk if the cost of a flight is low enough.

--Scott