New owners are a lot like new parents - the slightest cough or sniffle of their new "baby" sends them running for the doctor's (or vet's) office. That is perfectly natural. The bacteria heroin rehab facilities lands on heart valves and causes heart failure.
Instead the kitten flu is much more of a syndrome with a group of symptoms that are surprisingly similar for the human flu. The long list include how dogs bark too much, urinate inside the house, and dig a lot, also as how cats always lurk around the fish bowl or bird cage, eliminate outside of the box, and scratch its claws almost everywhere.