Hello,

I'm a developer from the CorsixTH project you might have heard of, it's an open source implementation of the theme hospital engine. We have a beta version of epidemics implemented but need some pointers to exactly how infected patients infect others.

At the moment the general idea patient A is contagious and patient B who has the same disease as patient A stands near or walks by patient A and then becomes infected themselves and then can go on to infect others in the same fashion.

Do the infected patients change the disease of any non-infected patients or is it just only infect ones with the same disease?

Why do you end up with a lot of infected patients when it's only a single disease that is contagious out of so many?

What makes epidemics "hard" to win?

Thanks for any input, happy to answer any questions about development too.

-- westforduk

I believe your assessment is correct - infected patients infect others with the same disease if they are close by (unless they have been vaccinated, obviously). That you can still end up with many infected patients is simple: often, epidemics occur in common diseases. Even in a somewhat large hospital, you have times where your operating theatre is hardly used but two pharmacies can hardly keep up - not all diseases occur equally often. I think you can validate this in the statistics screen.

What makes epidemics hard to win? Well, the way the game handles them - and I mean that in a slightly negative way.

1) Time runs out prematurely: Epidemics have to be cured in a strict time limit, but the timer may end abruptly once a patient leaves (and sometimes perhaps for no reason at all?). But this is a pretty big random event because the player cannot control and hardly predict it - if this means that you lose 40.000$ due to a fine, it's frustrating to say the least. A simple way to make this a bit fairer would be to adjust the fine to the amount of patients still not cured (with those not even vaccinated perhaps being assigned a greater weight) once the inspector arrives vs. the current everything-or-nothing system.

2) When does an epidemic get "detected"? Sometimes, you start with just a few infected patients (with those potentially infecting many more, of course) - other times, half your hospital is already infected in the beginning. It seems the trigger is the diagnosis of an infected patient - so being quick in diagnosing patients (without having them wander around long corridors) will help you find epidemics faster and give you a chance to vaccinate much sooner.

3) I think the main aspect that makes epidemics difficult is really how they pile up and punish bad player performance in multiple ways. Think of it this way: if you don't have enough money to buy new land, you'll have to build a more compressed hospital, hence tighter corridors. You also probably won't be able to keep up with the demand and may have longer waiting times. Hence epidemics get detected later, making them much harder to control. The fines will hurt you even more. On the other hand, if your hospital is well run, occasional small epidemics are a welcome money bonus as they are usually easy to handle.

But I think another fundamental question to ask in the first place is this one: when does an epidemic start? Clearly, there has to be one (or possibly even several) patients acting as source. Do they walk into your hospital already contagious? Or do they become contagious in the hospital? The game seems to suggest the latter (one of the briefings says a dirty hospital will increase the chance of epidemics) but I don't know how precisely this works.

Anyway, I hope this helps.
I have played CorsixTH a while back and found it already quite nice. Keep up the great work - I am sure anybody with a slight interest in this genre will truly appreciate your efforts.