Fertility & the Mumps
In some cases of mumps-induced orchitis, the disease ultimately causes a reduction in sperm production.... a paper published in 2010 in the “British Journal of Urology International” reports that it might involve changes in male hormones during the early stages of orchitis.... the viral infection causes swelling that can increase pressure on the sperm-producing parts of the testis.
Prolonged pressure may permanently damage the tissue, leaving it incapable of sperm production.... a reduction in sperm numbers in an ejaculate occurs in about 13 percent of men who have had mumps-related orchitis. Although this may lead to difficulty fathering
complete infertility is extremely rare.
Rare, perhaps, But I know two men so affected. They don’t have any sperm production. They lived in other countries as children (did not get vaxed against mumps) and did have mumps at puberty. Doctors assume that is why they are sterile.