My gaming group likes to count the player card deck when playing Pandemic so they know their exact odds of pulling an epidemic card at any moment. It's not my style, but I suppose it's really no different than counting cards in Blackjack - it may be frowned upon by the creators, but it's by no means against the the rules as there is no hidden information being exposed.

They spend so much mental energy though keeping track of this that I finally grew tired of it and made them a card holder that can keep each sub-stack of cards separate (each small stack that is shuffled in the setup of the game with an Epidemic card added to it). This allows anyone to quickly glance at how many cards are left in the top sub-stack and quickly determine their chances of drawing an Epidemic.

This holder holds 5 sub-stacks, each of which can comfortably hold 15 unsleeved cards (probably closer to 20 with no issue).

Q&A:

What if I'm playing Expert level in the base Pandemic game, or Iberia for example, and need 6 sub-stacks? - Put the 6th on top perpendicular to the top sub-stack.

Does this work for all Pandemic games and iterations? - I don't own all of them, but it at least works on the standard game, the Legacy versions, and most of the popular other versions. There is at least one version or variant that requires more than six stacks; I recommend printing two of these for that. There is a lip at the top and a recess on the bottom so you can nest two of these on top of each other for that situation.

Does this fit into the rectangular shadow on the board where the player card stack usually goes? - No. Move it a bit closer to Australia or off the board if need-be.

Will this hold sleeved cards? - I don't believe so. I would recommend scaling up the X and Y axes by 5% or so, and the Z axis by at least 50% or so to try with sleeves. Please leave a comment here if you find a good fit for sleeved cards.