Can STEAM Games also contain Viruses?

Well, I guess there can be!
But keep in mind that the dev has to pay a fee (I think it was 100 dollars) to be able to publish a game.
You can spread viruses literally for free, just by uploading a file/app containing one to some random file sharing website.

Lately, random indie games are not doing very well, so paying 100 dollars to get your virus to like 30 people isn't really worth it.

There have been games with spyware and mining trojans so I guess the answer is yes.

Actually there has been few cases especially with Sniper Ghost Warrior 3
https://www.reddit.com/r/JimSterling/comments/8qh7ie/psa_red_shell_spyware_found_in_many_steam_games/

I know there was a bitcoin miner in a game that was found because the developer was so inept that it didnt worked properly (ported his junk straight from mobile store), so yeah. Usually if you read the reviews there will be a mention of it if the dev doesnt delete those

I played a simple and slow fishing game that overheated so much (>80°c graphic card) that i wondered about a mining trojan. But maybe it was just very poorly optimized.

Some people consider Denuvo to be problematic DRM
https://denuvo.fandom.com/wiki/List_of_Denuvo_games