Even though there are no cases of West Nile here in Oregon, it is making the news here also.

Some general precautions include -

Get rid of any standing water (mosquito breeding grounds).
Don't go out at dusk (mosquito feeding time) unless you are wearing long sleaves and repellant.
Watch out for symptoms for those who are elderly or otherwise sick - younger, healthier people won't have as much of a problem and if exposed, will probably develop an immunity to the virus.

Also, you can do some searches on the web to see if you are in a state that reports cases of West Nile. From the most recent map that I saw, this is mostly in the east and central states. But I know that within a year or two, those of us on the west coast will probably be seeing it also. There is really just no way to stop something like this from spreading.