Mumps

Detailed Overview

Before the introduction of the routine MMR vaccine in 1967, mumps was a ubiquitous childhood disease. Today, outbreaks still occur, primarily in close-contact settings such as college campuses, even among vaccinated individuals due to waning immunity. The disease is usually self-limiting, but post-pubertal infection carries a higher risk of complications like epididymo-orchitis, which can rarely cause infertility. Supportive care remains the cornerstone of treatment.

Epidemiology & Demographics

Incidence dropped by >99% in the US post-vaccine. However, periodic outbreaks occur in young adults (18-25 years). It is highly contagious, spread via respiratory droplets.

Etiological Mechanism

Caused by the Mumps virus, an enveloped, negative-sense, single-stranded RNA virus of the Paramyxoviridae family, genus Rubulavirus.

Primary Causes

Transmission via inhalation of respiratory droplets

Direct contact with infected saliva or fomites

• Lack of immunization: Unvaccinated individuals are at the highest risk of infection and severe complications.
• Close-contact environments: Living in dormitories, military barracks, or attending crowded events facilitates transmission.
• Waning immunity: Outbreaks occur in fully vaccinated adults, prompting CDC to recommend a 3rd MMR dose during outbreaks.

The virus enters via the respiratory tract and infects the upper respiratory mucosal epithelium. It replicates locally and in draining lymph nodes, followed by primary viremia. The virus has a tropism for glandular and central nervous system tissues. It seeds the parotid glands, testes, ovaries, pancreas, and meninges. In the parotid gland, viral replication causes edema, lymphocytic infiltration, and desquamation of necrotic epithelial cells lining the salivary ducts, leading to the characteristic swelling.

Characteristic Clinical Presentation

• Parotitis: Painful swelling of the jaw/cheek area, often bilateral, exacerbating with chewing or acidic foods.
• Fever and Malaise: Low-grade fever (38-39°C), headache, and myalgias occurring during the prodrome.
• Earache: Referred pain from the swollen parotid gland.
• Testicular pain: In post-pubertal males, severe scrotal pain and swelling indicate epididymo-orchitis.

Physical Examination Signs

• Swelling obscuring the angle of the mandible.
• Erythema and edema of the Stensen duct orifice upon intraoral examination.
• Testicular tenderness, swelling, and warmth (orchitis).

• Orchitis: Occurs in 15-30% of post-pubertal males; usually unilateral. Can cause testicular atrophy, but sterility is rare.
• Aseptic Meningitis: Symptomatic in up to 10% of cases, presenting with headache, photophobia, and stiff neck.
• Sensorineural Hearing Loss: Rare (1 in 20,000) but usually sudden, unilateral, and permanent due to CN VIII neuritis.
• Pancreatitis: Presents as severe epigastric pain and vomiting.

Diagnostic Criteria & Guidelines

Clinical diagnosis based on characteristic parotitis in the context of an outbreak. Confirmed via laboratory testing for public health tracking: positive serum mumps IgM, or mumps RNA by RT-PCR from a buccal swab.

Differential Diagnosis

• Suppurative Parotitis (S. aureus)
• Cytomegalovirus (CMV)
• Epstein-Barr Virus (EBV)
• Salivary duct calculus (Sialolithiasis)
• Cervical lymphadenitis

Laboratory Tests & Biomarkers

• Buccal swab RT-PCR: Positive for Mumps virus RNA. Must be collected within 3 days of symptom onset for best yield.
• Serum IgM: Elevated mumps-specific IgM (may be falsely negative in previously vaccinated individuals).
• Serum Amylase: Elevated in parotitis and pancreatitis.

Imaging Modalities & Findings

• Ultrasound:

• Incubation
  Ranges from 12 to 25 days (average 16-18 days).
• Prodromal
  Fever, headache, anorexia, and malaise lasting 3-5 days.
• Acute phase
  Parotid swelling peaks in 1-3 days and subsides within a week. Complications arise here.

Second-Line & Adjunctive Therapy

For severe mumps orchitis: Bed rest, scrotal elevation, ice packs, and NSAIDs. In severe, refractory cases of orchitis, a short course of systemic corticosteroids (e.g., Prednisone) is sometimes used to reduce edema, though evidence of efficacy is limited.

Surgical & Procedural Management

None indicated.

Recommended Lifestyle Changes

• Avoid acidic foods (like citrus juices) which stimulate salivary flow and worsen pain.
• Strict isolation (droplet precautions) for 5 days after the onset of parotitis to prevent transmission.

Patient Counseling & Advice

Advise the patient on the highly contagious nature of the virus and the need for isolation. Explain that swelling will resolve in about a week. In adult males, warn about the risk of orchitis and instruct them to seek medical care if severe scrotal pain develops.

Follow-Up & Monitoring Schedule

Outpatient follow-up generally not required unless complications like severe abdominal pain, severe headache, or scrotal swelling occur.

Preventive Strategies

Routine immunization with the live-attenuated MMR vaccine: 1st dose at 12-15 months, 2nd dose at 4-6 years. A 3rd dose may be recommended by public health authorities during a targeted outbreak.

Excellent. Most patients recover completely within 2 weeks. Fatalities are exceedingly rare and usually linked to severe encephalitis.