New diseases! More pain!(winter)

[Kararas]

Oh, winter ... You know, there are a lot of illnesses from the cold, except frostbite. You can add a sore throat, pneumonia and a bunch of other "good." Drinking water from an ice-hole is not a good idea, as for me. I think boiling water or hot herbs  drinks in winter will be a fairly authentic idea. It is possible to realize a sore throat and a cold with a big cut of endurance and a fever. I think more than one person died during severe winters from illnesses.

[Privateer]

You can get the flu from villagers

.. Though I figured flu would be more dangerous 1300 yrs ago.

[Tom H]

Practically all of my characters have caught the flu once. One guy went almost immediately to 50% injury! There could be a greater instance of minor injury while conducting strenuous activities like logging trees and building traps. Said injuries would have to be cared for and medicated with the local herbs, too. I always have a lot of healing herbs that don't get used at all, save for seasoning cooking.

Regarding drinking icy water, I've always wondered why the water in my skins wasn't frozen. Maybe it's carried under my shirts? Anyway, if that's not the case, drinking water would likely require a warming fire, yes?

Perhaps these are supposed to be the hardiest types, inured to the worst conditions, unlike feeble villagers? While it would be a physical shock to be inundated in water, just drinking icy water probably wouldn't be detrimental to folks who work and live in these conditions, breathing the frigid air and being hearty enough to acclimatize in Arctic-like conditions. 

[Sami]

Oh, winter ... You know, there are a lot of illnesses from the cold, except frostbite. You can add a sore throat, pneumonia and a bunch of other "good." Drinking water from an ice-hole is not a good idea, as for me. I think boiling water or hot herbs  drinks in winter will be a fairly authentic idea. It is possible to realize a sore throat and a cold with a big cut of endurance and a fever. I think more than one person died during severe winters from illnesses.

Yes, new ailments, symptoms and diseases on all fronts could be added. Some are surely coming up in the future. And not only for the wintertime.

[Mati256]

No coronavirus, please!

[JP_Finn]

No coronavirus, please!

Some “common colds” are coronaviruses and sort of already in-game 
It’s just this 2019 one (96% match to some earlier known corona virus found on bats in China, then rated low risk... mutation is a b$7&h) that can and does spread asymptomatic with reasonably high mortality rate.

Vox produced “Explained” series episode(s?) of it, narrated by J K Simmons. Watched an episode last night.

Edit: it’s available on Netflix, not sure if it’s anywhere for free.

[Ara D.]

Mosquitoes in marshlands

[JP_Finn]

Mosquitoes are everywhere except sea, lakes mountain tops and immediate lake shore during sun light hours. Wind keeps them away.

The modern (northern) folks call it “räkkä” (mosquito season). It can get so bad, that the domesticated reindeer run up to the fells/mountains to escape the constant bloodsucking.