Mumps in Adults: Symptoms and the Bigger Risks

In an adult, mumps starts the same way it starts at any age — headache, fever, fatigue, no appetite — then swells the parotid glands. What changes with age is the tail of the illness. The complications that are footnotes in a five-year-old become the main clinical concern after puberty, and in the United States adolescents and young adults are now the group outbreaks actually hit.

Why the epidemiology flipped

Before vaccination, mumps was a disease of school-aged children. Incidence in the United States dropped by 99% after the vaccine was introduced in 1967 — and then the age curve moved. Twenty-first-century outbreaks in the U.S., Canada and Europe primarily affect adolescents and young adults, and they run through close-contact settings: dorms, athletic teams, fraternities and sororities.

Most of those cases are in people who were vaccinated. Two MMR doses are about 86% effective against mumps and one is about 72%, and immunity appears to wane. In a 2006 university outbreak, students vaccinated 13 or more years earlier were 9 times more susceptible than students vaccinated within the previous 2 years — which describes almost every American college sophomore.

Orchitis: the complication that defines adult mumps

Orchitis is the most common manifestation after parotitis, affecting about 1 in 5 cases of mumps among post-pubertal males. It causes painful swelling and tenderness of one or both testicles, and it typically appears a few days after the parotid swelling.

• Testicular atrophy develops in about half of those affected.
• Reduced fertility follows in up to 30% of cases.
• Pre-pubertal boys rarely develop infertility from it, which is the sharpest age difference in the whole disease.
• StatPearls notes no proven benefit from glucocorticoids for mumps orchitis.

The rest of the adult complication list

• Aseptic meningitis — described as the most prevalent mumps complication across sexes in the pre-vaccine era. A therapeutic lumbar puncture may relieve the headache it causes.
• Encephalitis, with generally low associated morbidity and mortality.
• Oophoritis, a rare complication in post-pubertal women.
• Mastitis, also rare.
• Pancreatitis, rare, presenting with significant abdominal pain.
• Deafness, rare but documented.

The third dose, and when it applies

Since 2018, U.S. guidance has called for a third MMR dose in people who already had two doses and are at increased risk during an active outbreak — the campus-notification scenario. Three studies found that third-dose recipients had a 61% to 88% lower attack rate than those with two doses. It is an outbreak measure, not a routine booster.

Get seen urgently for

Severe testicular pain or swelling, severe abdominal pain, and severe headache with neck stiffness, drowsiness or confusion. Any new hearing loss during or after the illness should also be evaluated rather than waited out. For the general timeline and the incubation window, see mumps symptoms; for how the same infection behaves in a young child, see mumps in children symptoms.

This content is informational and does not replace medical consultation, diagnosis, or treatment.