I was trying to figure out why EEE would make a horse test positive on a coggins, but what I know about EEE is very little (& I'd prefer to never have to learn--it's extremely rare here, WEE is more common)
Coggins is for swamp fever, aka "EIA". The tests for EEE and WEE are different. Survivors of EEE & WEE do not need to be euthanized or kept quarantined for life.