Orchitis is swelling (inflammation) of one or both of the testicles.Alternative Names
Epididymo-orchitis; Testis infectionCauses, incidence, and risk factors
Orchitis may be caused by an infection from many different types of bacteria and viruses.
The most common virus that causes orchitis is mumps. It most often occurs in boys after puberty. Orchitis usually develops 4 - 6 days after the mumps begins. Because of childhood vaccinations, mumps is now rare in the United States.