if you think your horse is sick keep it home and call the vet don't put other horses at risk it would be nice to have a website or some sort of notification that an outbreak is in an area that you may be taking your horse to so that you can make the decision to risk it or not
If there was only a way to check ahead of time, because most insect disease take a few weeks if not months to show up.
Until then, try Outbreak-alert.com You can find out whats in your area or whats going on where you may be traveling to.