UPDATE: Everything is fine.
Turns out, my eldest cat Darby (and likely the new kitten. If not now, then he soon will) has
Feline Viral Rhinotraceitis (also known as Feline Herpes and/or Feline Influenza) and was just having a flair-up in reaction to the new kitten arriving in the house last week.
Vet says both will be just fine.
Apparently, this disease is so common that to use a proper analogy, it would be like going to Japan, and assuming that everyone you meet speaks Japanese as a first language. The people that don't speak it as a first language are the exception to the rule. Likewise, the cats that do carry this virus and never show symptoms are the exception to the rule.
I found it fascinating, because our family cat lived a good 14 years and never once did he have any problems related to it.
But boy, am I relieved. Darby got an anti-biotic shot, and we got some Lysiene supplement, which will prevent viral replication and flair-ups.
Both kitties should live long, happy lives!!!
