... even if their medical technology lagged behind Earth's, it would still be fairly advanced, unlike the indigenous Americans or Classical era people during the Julian plague.
No doubt. Now think about the
culture implied by the statement, "...even surgery was largely freed from the danger of infection."
(Leave aside for a moment the fact that the statement carries with it a certain lack of knowledge of disease: some of the more serious surgical infections arise from organisms living in the human gut, on human skin, or in the human nose, which is why doctors mask and wash up - although, I guess it's possible the Ancients made efforts to sanitize their transportees, in which case things could be far worse than we imagined.)
The Vilani've encountered disease: they almost surely have a few of their own circulating about and some idea of how to deal with them. They probably have an understanding of epidemiology: humans are the primary disease vector, so dealing with spread between humans is a big part of their disease program. Human diseases resulting from poor sanitation will be a possibility in any human society, so they'll have a knowledge of those and how to prevent them. However, infectious disease is uncommon: infectious disease experts will therefore be rare. Physicians will have a basic school-taught knowledge of infectious disease and infectious disease process, but their practices wll have little experience of them. And, the Vilani are famously conservative.
A flu pandemic will come on them like the Spanish Flu epidemic - it will spread fast and hit hard. Because these are people with no previous exposure, it may run much like the Spanish Flu did, hitting the healthiest folk the hardest. For Spanish Flu, the killer was not the bug but the immune system response to it: those with the healthiest immune systems drowned in their own phlegm as the body reacted to the buggie, while the elderly and infirm tended to have a higher survival rate.
In a culture known for its conservatism, the Vilani medical community will have to hunker down and figure out why it's happening, then develop strategies to ameliorate symptoms, to diagnose and treat the new diseases, and to interrupt their spread. The real challenge isn't treatment. It's epidemiology: figuring out how the bug spreads, finding ways to interrupt that spread,
and convincing health care providers and the general public to adopt those ways.
As the disease spreads beyond a certain point, tech will become less relevant because there will simply not be enough of it to treat all the affected people, so the crucial factor will be how quickly they can persuade a conservative culture to adopt such basic things as quarantine and the importance of wearing a mask while caring for an infected person.
And they're going to have to do that while the buggie sweeps preferentially through their own medical community, since the first place the sick folk will go will be to their doctors and hospitals.
The real threats are not likely to be the classical threats. Even if Terra has not conquered the classical threats by then, odds are good it's not about to allow people to ship out who are infected with those diseases. The real threats are likely to be things the Terrans consider benign, innocuous, or too much trouble to eradicate. Candida Albicans: been around millions of years - could it have changed so much that a population 300,000 years removed from the Terran strain might be vulnerable to painful thrush? (Or vice versa?)Salmonella: it's been around for millions of years, but the Ancients are unlikely to have take it with them, and the planetary origin of a particular host might make little difference to the buggie - some Terran starts up a chicken ranch, eggs get eaten by a local predator, predator takes a poop, salmonella starts working its way through the food chain and preparing suprises for the locals.
