Why is it more probable to come down with orchitis during an infection of mumps?

Common Site. With the mumps virus (as well as similar viruses), the testes are a common site for inflammation. It is unknown why certain viruses effect certain parts of the body, but it may be due to the type of cells in the area and their function. There has been a dramatic increase in mumps orchitis seen in the past few years. This is most likely due to the increase in unvaccinated or poorly vacc. Males.