A few cycles ago I had a problem with a bit of high stress, so one dup with Hypothermia vomitted. Interestingly enough the water had Hypothermia-Germs in it but it seems like they are not fully implemented yet (They do not spread/live/die on any kind of thing and just exist). But exactly that is the problem now because after not taking a look on my base for about half a cycle or so, the bottom half of my base is complettly infested with it and the immune system of my dups is pretty much not existing. And because there is no reasonable temperature or any other way of killing them I can't see those Germs go time soon.
I think the spontanious spread could be due to me placing some Algea Terrariums in the water.
Maybe trying to make a dup who has Hypothermia puke and then try to water your algea terrariums with the water.