How soon do symptoms of TB disease appear, after a person gets infected with TB bacteria?

This depends on the person’s age, his/her immunity system and among small children on vaccine protection. Children less than five years old who have not received BCG vaccination, can get sick rapidly (even one month after they get infected with TB bacteria).
Adults whose immune system is normal can get symptoms within 6 -12 months after infection with TB, but the delay can be decades long. TB bacteria can lie dormant (sleeping) in their body (latent TB infection) and the infection can develop to TB disease later when their immune system gets weakened because of ageing, diseases or medication.

TB disease