I recently started playing Betrayal at Krondor as abandonware. It is my first time playing the game and I did not play it back in 1993. One of the many things which can happen to characters in BAK is a disease status. Typically, there are certain encounters that will inflict a disease state on the party, such as attempting to explore a house which is considered to contain a diseased individual, or certain random encounters where the enemies theoretically have pelted you with diseased materials. (I've gotten the disease status from that encounter even when the opponents did not succeed in striking any of my PCs a single time.) Since I work in a health field these events actually annoyed me tremendously because in reality there are practically speaking no diseases you're going to encounter which are that contagious. Personally, I've been in the same room as people with tuberculosis, including active TB, over a period of nearly two years and I have not been infected. A doctor I know who personally sees and evaluates each patient on the island hasn't been infected even though he's seen new and suspected cases face to face with no masks or anything for many years now. The way that diseases and illnesses are handled in role playing games is very unrealistic and for me that always hurts my suspension of disbelief.
Now I have to relate this to Shadowrun so that the mods don't poleaxe me.
This is similar to becoming infected by a ghoul in Shadowrun. I don't have my sourcebooks with me and haven't seen them for 2 years so my memory is becoming increasingly faded but as I recall the only condition which is required to infect your character is a single successful ghoul melee attack. Therefore, the treatment of infectious diseases in Shadowrun is similar to the treatment in most RPGs; that is to say, transmission is unrealistically easy.
(In reality, the probability for something like that any one time is quite low. According to the health handbook I have here, the risk of HIV transmission following a needle stick from an HIV positive positive person is only 1 in 200-500.)
I personally think that it would be more interesting if diseases were handled in a more realistic manner. It would add more dimensions to gameplay. I think it's analagous to making the firearms rules more realistic and less cinematic. If we're talking about diseases, it's no longer about "nyah nyah nyah, the bum stabbing me with the HIV infected needle didn't get any successes on his attack roll but had he got a single success I'd automatically be infected", but rather about a broader range of sanitation and health issues with more complex planning attached to it.
What are some of the issues we would end up looking at instead? Well, fundamentally, maintaining good health is about managing probabilities of risk. We exercise and eat healthy because it reduces (but does not eliminate) the probability of death by heart disease. We can choose to ignore hygiene and not treat open cuts either in the interests of expediency or for in-character reasons but this would increase the probability of getting a staph infection which in turn increases the probability that beyond swelling and pain at the site of infection we might possibly be incapacitated with an infection-related fever. We can dive into the sewage to hide from the Renraku Red Samurai and it might be the best course of action at the time but if we've later got to deal with the possibility of hepatitis, leptospirosis, etc. We should weigh the probability of being killed by the RRS versus the risk of our stats being badly erroded by these various diseases later.
Sanitation, in my mind, provides a lot of interesting material for any military or mercenary themed game. The military has certain procedures to ensure field sanitation and this is because it's a well established fact that armies can and have been weakened or disabled due to disease. How do the PCs ensure adequate levels of sanitation in the field? I think this adds depths to gameplay or if nothing else in-character thinking.
Exposure to diseases becomes more nuanced. It shouldn't be, "oh no, you were stabbed with the needle, now you're screwed." I think it's much more nerve-wracking and interesting if you don't really know if you're infected or not. That's where the probabilities come in. Imagine if you somehow did end up getting stabbed with a HIV infected needle. You know your odds are pretty good of not being infected (see above) but depending on your personality the possibility that you *could* be infected, and that you couldn't find out for a while since you'd need to wait for the "window period" to elapse before getting your HIV test could really kill you.
I just think that the real world has a lot more to offer in terms of complexity and interestingness if we look at real medical information regarding disease and sanitation in our RPGs than if we fall back on the tired and cliched Hollywood paradigm of instant infection upon the slightest exposure.