What if you launched a token on blockchain that acted just like a virus? Whenever a wallet with the token in it transacts with another wallet, a new virus token is created and transferred. It wouldn't take long for everyone to have these tokens in their wallets.
The token wouldn't be worth anything because it would be highly inflationary. The game would be eradicating the virus. Launch a dApp that gives players tools to combat the spread of the virus and eventually create a vaccine.
This could be a lot of fun, but it does introduce scalability concerns. Any time you're creating a large number of tokens and transactions, you're putting stress on the network.
Either way, this could be a very interesting case study. I don't see something like this working on a blockchain with gas fees, but it might with the right design.
P.S. If it works out, give players the ability to customize and launch new virus tokens.