In response to Mark's first question, no. I'm not saying it has never or cannot happen, just that I've never seen that reported AND it doesn't make sense. The body can be overwhelmed, but no reaction seems far fetched.
Second: We have been getting guidance from State Veterinary borard, AVMA and AAHA and all recommend reducing human to human contact. To that end they recommend not having people come in the hospital, rather have a hospital employee get the animal from the car then take history, etc. by phone while the vet is examining the animal. This is a cumbersome, time consuming process but seems prudent. Also, they are recommending delaying routine procedures, vaccination. I'm not sure that's reasonable as this thing is likely to go on for a while.