Not sure if this is the best place for this, but... I am working on a story and am looking into assorted diseases/disorders that affect animals and how those illness would affect humans, if they somehow managed to become contagious across species. Now, it's easy enough to make the connection between mammals, but for other animal types, it's a little less straight forward. So anyway, there are two parts to this question: 1) What are some serious diseases/disorders that are known to affect reptiles, bird, fish, and/or amphibians but that do not affect mammals? (i.e. what is the WORST disease you can imagine your non-mammalian pet getting? Looking for answers for each of the 4 animal groups mentioned above, not a single illness that works on all of them) 2) How do you think that disease would affect a human, if it managed to cross species? Remember, this is a work of fiction, and fantasy at that, so don't worry about the actual science and plausibility of this happening. It's just a matter of trying to get a feel for what are regarded as the most serious animal illnesses and how those types of things would present in a human patient.