Procedural Hidden Information Mechanics

I do not think it can be done. There is always one thing missing.

If it starts in a and grows that I think can be done as you said with relative eas. But to have it spreadind without another player controling it can not be done unless you have rules for how it spreads. And that is also fine the onley problem is you have to check the ground zero al the time to know it it has spread so you have to know exactly how bit it is. Every time you go to a new location you would have to check on groundzero to se if it have reached there yet.

So the onley way to solv it I would say is to have a player controling it. Or atleast that would be the easiest and simplest way.

You might be able to do it if you have a preprogramd grothpattern that is random on the map but grows exponentialy over time. Think of it as a mix between pandemic and a traitor game.
You place the groundzero marker in a city. The first turn you take a deck of cards, the deck consists of infe3cted and not infected cards and the dificultylevel is in how manny you have of each, you deal out one of thees cards to every adjacent city. The next turn you do this again but this turn you also deal one card to the citys that are next to al citys with a card, also you put in more infectd cards. This way you have "hidden" information, ither the city is infected or not. Also when you go there you take ths stack of cards and flipp them over, this way you have the oldest card first. Now you go throu it to se if and when it was infected. Then depending on when you know how bad it is now, like it was infected 4 turns ago so now half the city is infected or somthing simular. This way you will have a spread from groundzero and a logical groth. And maby you can add a "if the city have 5 cards it is infected" even if al of the cards says uninfected, or you have a valu on the uninfected cards and you tally up thoes and when they reach a certan number the city is also infected, this way you can have new "random" outbraks simulating people going from the groundzero there. The random number should be withing a prity narow span and the players should be awar of what the avarage number per card is so they can do rufguesses of when the citys should be infected. This way you can have the players arguing about if they should go and save it now or wait, it might not be infected yet we do not know for shore and so on. The biggest thing about a game like this I would say is how you design the map.Becaus if you do a airspread virus then the map is a limiting factor for the players sort of simulating reality. And if you do a human to human virus then ot spreads along the same paths making it a difrent game, one with more strategy in it. "what city should we go ti first, this one that have bin infected the longest or this mor strategic one. From here the virus could spread out to numurus other citys" This can be done using a river or mauntain range as a natrual obsticle onley alowing the virus and players to cross it on sertan locations.

Atleast that is what I would do.

I read your thread rapidly, if I understand correctly, you want infection to spread but you actually don't know if there is enough infection tokens in the stack to actually spread since the information is hidden.

I have 2 solutions which has their pro and cons.

A- When a player visit an area he reveals the tokens, if the infection level is too high, it will spread to neighboring cities. The problem is that players could prevent themselves from exploring a location knowing it will explode. So you might need mechanic to force players to visit unvisited cities.

B- After a certain number of tokens, whatever is their content, the infection spread. Use the law of average. If 1/2 of your token increase infection level by 1 and you need 5 level for the infection to spread, in average, if you have 10 tokens in a location, you should have reached level 5. So either you reveal the token and spread the infection for leave the tokens there and add new tokens in the adjacent areas.

You can also combine both mechanics if you want.

I like DogBoy's approach. I'll have information revealed BY the players TO the players as they manage to fit it in a consistent chain of information previously revealed.

I've seen all kinds of debates on virus expansion mechanics since Pandemic. If I could afford the time, I'll work in twisting the virus game backwards. That is, working on a "containment" mechanic instead of in a "contagion" one, not done by the game, but by the players.

So, here's the example. Say a plague spreads in the country and you have to contain it by sanitizing (¿english?) every city in the board. Use the Tobago mechanic. During his turn, a player uses a card with a certain condition discovered about the virus ("cannot live in coastal environments", "cannot tolerate high temperatures", "requires heavy population density"). This will progressively reduce the "endangered cities" in the map, untill all cities are safe from the disease. Voilá! problem solved.

I tried to keep it short. Hope this makes sense. Keep thinking!

For this idea you will need a tile for every single square on the board. But I think this would work.

Lets say there are 100 spaces on the board.
So then you have 3-5 ground zero tokens and 15-25 infected tokens.
Shuffle the tokens and place them face down on the board.
When a player moves over/to a space flip all touched tokens over.
If the player runs into an infected token then they suffer the consequences (whatever they may be, attack/movement minus etc...)

For every ground zero token flipped ALL infection tokens increase by 1: they are now able infect 1 square out in every direction.

So that by the end of the game each infection token extends out 3-5 spaces around it.

I know it's not a true "ground zero" expansion pattern. sorry about that