Mixing Kittens Safety

I'm a fairly experienced rescue/foster. I have a litter of three 7wk old kittens who were very malnourished but have recovered significantly in the past 2 weeks. I found and quarantined a single, unrelated, 7wk old kitten yesterday. I know that this new kitten came from a litter in which 3 had very bad eye infections, which suggests to me FHV. However, this kitten looks normal. The infected kittens were rescued 10 days ago and this one has been separated since. For certain reasons, this single kitten is unable to be reunited with it's siblings. What are the chances that this new kitten will infect the other 3? The other 3 are still too small to vaccinate. But I hate to keep the single kitten in isolation. Thanks in advance!

Hello - I hear that you dont want the kitten to be lonely.  On the other hand, mixing them is poor biosecurity; you know nothing of the backgrounds of either set of animals except that they are unlikely to have come from a good home, that one set look to be carrying a viral disease and that their parents may not be vaccinated.  At seven weeks, the most open period of the 'socilisation window' - where cats learn to be cats, socially speaking - is just about closing, so the benefit of introducing the kitten to other cats NOW as opposed to, say, in a few weeks time, may be less than you think.   Therefore, I would suggest keeping the kittens separate and practising barrier nursing between them.

However, please note that your vet knows more than me about their circumstancs and any advice gien by your vet, who knows the intricacies of a particular case, will always trump any general suggestions made by a vet who knows nothing about your circumstances.  You should always seek their advice.