I live in a new house that was built 3 years ago. Recently we have noticed a strong sewage smell coming from the drain ( the smell hasn't always been present). What can I do to remove the smell?

Try running about a half of a gallon of water in the drain, if it stops the smell then what I'm thinking is that there is a venting problem and it's creating suction that's pulling enough water out of the p-trap to create a gap for the gases to escape.

Also if it's not you main shower, the p trap is going dry and just needs water added every so often.