Mumps is a highly contagious viral infection caused by a member of the Rubulavirus family. This disease, once common in childhood, typically presents with non-specific symptoms like fever and headache. The most recognizable sign is the painful swelling of one or both parotid salivary glands, known as parotitis, which gives the jaw and cheek area a puffy appearance. While the infection is often mild, the virus can spread beyond the salivary glands and affect other organs, raising concerns about long-term reproductive health.
Mumps and Reproductive Organ Inflammation
The mumps virus has the potential to infect glandular tissue throughout the body, leading to inflammatory complications in the reproductive organs of both males and females. In post-pubertal males, the most frequent complication is mumps orchitis, which involves the inflammation and painful swelling of one or both testicles. This complication generally occurs four to eight days after the onset of parotitis, though it can manifest without salivary gland swelling. Post-pubertal males are susceptible because the virus targets testicular cells involved in sperm production and hormone synthesis.
For post-pubertal females, mumps oophoritis is the inflammation of the ovaries. Oophoritis is less common than orchitis, occurring in about 5% of women who contract mumps after puberty. Symptoms, such as lower abdominal pain, are typically short-lived and resolve once the acute infection passes. Fertility risk focuses predominantly on males due to the higher incidence and severity of the inflammatory event in the testes.
Determining the Risk of Infertility
The risk of fertility issues arising from a mumps infection is directly linked to the development and extent of mumps orchitis in post-pubertal males. This testicular inflammation affects 20% to 30% of post-pubertal men who contract the mumps virus. The inflammation can lead to significant swelling within the confined space of the testicular capsule, potentially causing pressure damage to the delicate seminiferous tubules where sperm are produced.
The impact on fertility depends on whether one or both testicles are affected. Mumps orchitis is bilateral (affecting both testicles) in about 10% to 30% of cases. When inflammation is limited to one testicle (unilateral orchitis), the unaffected testicle can usually compensate for sperm production, making long-term impairment less likely. However, bilateral involvement significantly increases the likelihood of fertility problems.
Estimates suggest that men who experience mumps orchitis have a subfertility rate of around 13%. For those with bilateral orchitis, the risk of developing subfertility or infertility is much higher, ranging from 30% to 87%. This impairment is characterized by reduced sperm count or quality, resulting in oligospermia or even azoospermia (complete absence of sperm). Complete and irreversible sterility is a rare outcome of mumps, even following bilateral orchitis. Mumps oophoritis in women is not known to lead to long-term fertility issues.
Prevention Through Immunization
The most effective method for preventing mumps and its associated complications, including reproductive organ inflammation, is vaccination. The measles, mumps, and rubella (MMR) vaccine provides protection against all three diseases. The standard immunization schedule typically involves two doses given in childhood.
A full two-dose course of the MMR vaccine is highly effective at preventing mumps infection, with efficacy reported in the range of 86% to 88%. By preventing the initial viral infection, the vaccine eliminates the risk of mumps orchitis and subsequent fertility impairment. Even if mumps occurs in a vaccinated individual, the symptoms and potential complications are often significantly milder. Vaccination remains the most straightforward public health strategy to protect against the reproductive health risks posed by the virus.