Hello, I'm fairly new to the game but am enjoying it thus far. One thing I would like to see is a system of ailments ranging from mild to severe. A lot of the potential is already there for zoonotic transmission of things like Influenza. Common cold could be another mild one that slows you down a bit (maybe gets worse if not treated gingerly?) Person to person transmission and seasonal variations in the appearance and spread of certain diseases could also be interesting.
Sorry for the random and poor format, I am on my mobile phone.
A few diseases that seem plausable could be:
Rhinovirus (person to person and mild, seasonal)
Influenza (Zoonotic and contagious, seasonal variations)
Yellow Fever (mosquitos could be added as the mode of transmission?)
Tuberculosis(severe and long term, the only issue i have is a method of transmission since I'm not aware of any other primate species running around in h&h)
Cholera (once again, transmission poses a problem because human waste isn't an issue... but definately an interesting disease)
Smallpox (highly contagious, person to person transmition, believed to have mutated from a rodent virus. Cowpox from domestic and wild cattle could be related, only causing mild symptoms in humans and making them immune from smallpox)
I believe I saw Lyme disease as a suggestion and it would work very well alongside other insect transmitted disease
Plague (perhaps a step too far, highly contagious, fleas/rats as methods of zoonotic transmission)
Consequential ailments like Emphysema from tobacco use (tobacco use or other breathing issues could increase chance and severity of other respiratory infections)
As far as curing, mild issues like the cold, for example...could be improved with herbal teas or perhaps a chicken soup? Herbs like horehound could be crafted into remedies.
Bacterial infection could be helped by somehow making baked bread grow mold for a penicillin-esque antibiotic effect
Variolation could be implemented in a way, taking some physical part of the disease from an infected person (scabs, etc) and preparing them in some way (smallpox was dried and ground...both of which are already possible) and applied to a purposely made wound in the person being variolated. This could carry a risk of the disease running rampant in the person (it was a small percent right around the time the vaccine overtook it as the prefered method)
I know its been mentioned in the past, but with the last FB post mentioning the lack of contagious disease and the current world situation really sparking the passion I have for epidemiological history compelled me to throw my ideas out there. Sorry if anything is repeated elsewhere.
Thank you for reading!