Probably not new news over there, but in case it hasn't crossed the pond yet:
Whatever virus strain kicking up in cattle and some wild mammals over here (highly pathogenic avian influenza - H5N1) is having a really horrific record of killing house/barn cats exposed to it. (Apparently it's around 50% lethality.) So, if your kitty goes out and kills a bird or a mouse that is a carrier, you may lose your little furry friend. There was a version of H5N1 that was floating around in Europe a few years ago that was also having a bad outcome for cats. Not sure if what's flying here is a mutation of that one, or a new mutation, though from what I'm reading it seems to be a newer variant.
TLDR? It might be time to consider making your indoor/outdoor cat an indoor-only. It can be done.