The number of teenage boys and young men developing mumps orchitis is increasing and there is a need to offer the MMR vaccine to unvaccinated males in the 15–24 age group, according to urologists at a leading Irish hospital.

This problem causes one or both testicles to swell and can lead to fertility problems, hence the importance of educating young males about the condition.

Niall Davis, a urology research registrar at the Mater Misericordiae University Hospital, Dublin is with colleagues conducting a review of five decades’ worth of research and statistics.

Up to 50% of males with mumps orchitis will experience testicular atrophy, where one or both testicles reduce in size. Even if testicles have not reduced in size, infertility is rare, but subfertility can occur in about 13% of patients, review said.

Half of patients can experience abnormal sperm for up to three months after recovery and 24% of adults and 38% of adolescents still have abnormal sperm up to three years after recovery, review said.

Mumps orchitis with reduced testicular size is the risk factor for testicular cancer.