Cam is dipping a grilled cheese sandwich into a bowl of tomato soup when he feels the summons. He goes ahead and grabs it. Doesn't even drop the sandwich.
"Not anymore, thankfully. There has been significant progress on multiple social fronts since the Empress Hikari took power. That said, people will find you distasteful at best if you admit to cutting up corpses." There's a wry twist to her voice.
"I hope they're practicing decent hygiene. Corpses are very informative things but sometimes people who die turn out to have been sick."
"And the people who perform autopies become sick as a result. Yes. We have at least noticed that link, though we don't know exactly why it occurs. Of course, the traditionalists insist that it's because we're desecrating the dead and thereby incurring their wrath, but if that were truly the case, why would they so consistently curse us with the thing that killed them? And only when it was a particular sort of disease? Clearly, it's no more blasphemy than associating with those who are sick but alive."
"Okay. Most diseases, all contagious diseases but not the ones that just run in families because that's not contagious, are composed of organisms too small to see parasitizing the infected person. A lot of the common symptoms like fever are the body trying to fight them off. Vaccines work because they teach the immune system what a disease looks like without being strong enough to make you sick all by itself - the immune system is mostly some specialized cells in the blood which can sometimes make mistakes about what's a disease, and cause allergies."
"Slow down a second and let me think. Animalcules cause diseases by parasitizing the infected? That sounds... vaguely reasonable."
She pauses significantly.
"So... assuming your knowledge holds, most transmissible diseases are caused by the movement of tiny parasites from one person to another. Let me guess - boiling kills these parasites? They cannot withstand heat, and that's why the body fights them with fevers?"
"Boiling kills 'em, they don't love heat but fevers are actually not that effective so it's safe to take symptom-reducing medications. There are two meaningfully different kinds of 'animalcule's that are most often operative, bacteria and viruses. Bacteria can be killed by a class of drugs called antibiotics, because they are alive in a fairly conventional way. Viruses are not alive in a conventional way and need different, more advanced drugs, or just symptom control and vaccinations. Some infections are instead caused by prions or protozoans or fungi or multicelluar parasites, the former of which are less alive and the latter several of which are normal amounts of alive but which you should identify so you don't try to kill them with something specialized for bacteria."
She steeples her hands.
"... I've been following an alleged ritual practice of the New Lupinians by washing my instruments in purified alcohol and then water between surgeries. It appears to work, so far as I can tell. Does that also kill the animalcules, or have I just been lucky?"
"Alcohol's pretty good for it, yes, and it doesn't take high tech to distill all the animalcules out of naturally occurring water. Also peroxide, radiation, some other stuff."
"Remember I mentioned the part of sunshine that I thought might set vampires on fire but turns out not to? There are a lot of invisible light-like things like that and radiation is the general term and some kinds are really good at sterilizing stuff."
She tilts her head.
"Come to think of it, that raises a rather interesting question - perhaps vampires have some form of animalcule? Oh, but we've eliminated 'ultraviolet' already."
"Sunlight doesn't produce really strong ultraviolet, or it would hurt humans, who are also pretty easy to kill with substantial quantities of many forms of radiation. Aaaand I don't think a kind of animalcule would explain you catching fire. There are conditions which cause extreme sensitivity to light but not literally catching fire."
"It would explain the transmissability... but then again, vampirism doesn't exactly work like a disease. You have to will it. So it is a strange animalcule indeed, if it is one."
"Yeah, animalcule-based disease transmission has no clear mechanism by which it could matter if you willed something."
She shrugs.
"So, since it has been determined that you'll be staying with me for some time - would you like me to provide a room for you?"
"Probably more convenient than me skulking around the halls at all hours of the day, although since I wasn't planning to sleep it's not urgent."
She opens another door, producing another empty room, this one of middling size with a window.
"Go ahead, work your magic."
"No-one other than me and mine will ever see this room, so feel free to generate as many otherworldly things as you like."
Cam has fairly conservative decorative tastes, but he puts in a nice abstract-patterned rug and nice curtains and a hammock, and a big-screen TV/monitor (to which he attaches the computer he's holding) flanked by a pair of speakers, and a chair with a squooshy back suitably for comfortably sitting in while winged.
"My books are all on here," says Cam, pointing at his computer. "I mean, except the ones you gave me, which I am going to read and then put back in their library. I can always add a case if I acquire a permanent family of physical books."