Years ago when I adopted a cat from the humane society with a bad viral URI, the vet told me about L-lysine supplements, he said to sprinkle a capsule into his food, about 500mg per day. The cat got better quickly. He was picky while sick though, I had to mix it into tuna to get him to eat it. It's better to do it in 2 divided doses in the morning and evening so it's more evenly in his system.
L-lysine suppresses viral replication, makes the virus unable to reproduce so it dies quickly. You can use capsules meant for humans, it helps with the flu for you too.

Sent from microwave via Tapatalk ll