EHD runs in cycles - examination of historical data suggests a 9-yr cycle with a 4-yr cycle superimposed on it - so...you can count on a significant event every 4-5 years, with a few cases here and there virtually every year.
Whitetail deer are most impacted, but cattle and other ruminants are very frequently infected with the EHD virus during these epizootics - but we rarely see clinical disease in infected cattle. I've seen a few through the years; almost always a single animal here and there - have never seen more than one affected animal in a herd. Most clinically-affected cattle survive and recover, but deaths do occur. Affected animals I've seen personally had fever, were depressed, didn't wan to move- their feet hurt! - muzzles are dry and cracked - look like you burned 'em with a blowtorch, and their dental pad is ulcerated, may see excessive salivation - not sure whether they're actually salivating excessively, or if they have difficulty swallowing.
Saw reports and photos of clinically affected cattle out of Nebraska, earlier this week; have had no reports of affected cattle in KY this year(had 'em in 2007), but we're seeing it in deer.
No need to worry much about it - there's really nothing you can do to prevent it, but if you have an affected animal(unlikely to be more than one), good supportive care - especially making sure they can get water - is about all you can do.
