Mumps
Acute viral infection caused by mumps virus (Paramyxoviridae) characterised by fever and painful parotid gland swelling. Vaccine-preventable with MMR. Complications include orchitis (20–30% post-pubertal males), meningitis, and pancreatitis. Notifiable disease.
Key Facts
Parotitis: bilateral painful parotid swelling in ~70% of symptomatic cases — pathognomonic appearance Orchitis: 20–30% of post-pubertal males; usually unilateral; subfertility rare (~1%) Meningitis: ~10% of mumps cases; usually self-limiting aseptic meningitis MMR vaccine: 2 doses; 88% effective after 2 doses against mumps (less effective than measles component) Sensorineural deafness: ~1 in 20,000 — usually unilateral; was leading cause of acquired deafness in children pre-vaccine era Notifiable disease: must be reported to local health protection team Incubation period: 14–25 days (average 17 days) Outbreaks continue in universities/young adults — often in those who received only 1 MMR dose
Overview
Key Facts
Mumps is a systemic viral infection with predilection for glandular and nervous tissue. Despite MMR vaccination, outbreaks still occur, particularly in young adults in close-contact settings.
Epidemiology
- UK: ~1,000–5,000 confirmed cases/year; periodic outbreaks in universities
- Most cases in 15–30-year-olds (born before complete 2-dose MMR programme or received only 1 dose)
- Pre-vaccine era: ~1,200 cases/100,000/year
- 30% of infections are subclinical
Aetiology
- Mumps virus: Paramyxoviridae family, genus Rubulavirus; single-stranded RNA
- Transmission: respiratory droplets, direct contact with saliva
- Incubation: 14–25 days
- Infectious: 2 days before to 5 days after parotid swelling onset
Pathophysiology
- Virus replicates in nasopharyngeal epithelium → viraemia → tropism for glandular tissue (salivary, pancreas, testes, ovaries) and CNS
- Parotid inflammation: lymphocytic infiltration, oedema, ductal obstruction
- Orchitis: interstitial oedema and lymphocytic infiltration → seminiferous tubule damage (rarely causes complete infertility due to usual unilateral involvement)
- Meningitis: direct viral invasion of meninges
Clinical Presentation
Typical Presentation
- Prodrome: fever, malaise, headache, myalgia (1–2 days)
- Parotid swelling: painful, bilateral (70%) or unilateral; earache, difficulty chewing
- Jaw angle obliterated; earlobe pushed upward and outward
- Swelling peaks at day 3, resolves over 7–10 days
Complications
- Orchitis: 20–30% post-pubertal males; painful testicular swelling 4–8 days after parotitis; usually unilateral
- Oophoritis: 5% post-pubertal females; pelvic pain
- Meningitis: ~10%; headache, neck stiffness, photophobia — usually self-limiting
- Encephalitis: ~0.1%; more serious, seizures, altered consciousness
- Pancreatitis: ~5%; epigastric pain, vomiting, raised amylase
- Sensorineural deafness: ~1 in 20,000; usually unilateral
Red Flags
- Severe headache and neck stiffness (meningitis/encephalitis)
- Severe testicular pain and swelling
- Severe abdominal pain (pancreatitis)
- Altered consciousness
Differential Diagnosis
| Diagnosis | Key Features | Investigation |
|---|---|---|
| Bacterial parotitis | Unilateral, purulent discharge from Stensen's duct, elderly/dehydrated | USS, pus swab for culture |
| Parotid calculus (sialolithiasis) | Intermittent swelling with eating, palpable stone | USS, sialography |
| Parotid tumour | Painless, progressive, firm mass, facial nerve involvement | USS, FNA, MRI |
| EBV (glandular fever) | Pharyngitis, generalised lymphadenopathy, splenomegaly | Monospot, EBV serology |
| HIV parotitis | Bilateral, painless, cystic parotid enlargement | HIV test |
| Sjögren syndrome | Dry eyes, dry mouth, bilateral parotid swelling, arthralgia | Anti-Ro/La, Schirmer test |
Diagnosis / Investigation
Bedside
- Clinical diagnosis: bilateral parotid swelling in appropriate context is usually sufficient
- Temperature: fever monitoring
Bloods
- Mumps IgM: positive from symptom onset (oral fluid sample preferred in UK for UKHSA confirmation)
- Mumps PCR: buccal/throat swab or urine
- Serum amylase: elevated (parotitis and/or pancreatitis)
- FBC: leucopenia or normal; may see lymphocytosis
- LFTs: mildly deranged in some cases
Imaging
- USS parotid: if diagnosis uncertain or abscess suspected
- USS testes: if orchitis — exclude testicular torsion
Special Tests
- LP: if meningitis — lymphocytic CSF, elevated protein, normal glucose, mumps PCR in CSF
- UKHSA confirmation: oral fluid sample for IgM (gold standard in UK surveillance)
Management
Non-pharmacological
- Supportive care: rest, oral fluids, soft diet (chewing worsens pain)
- Isolation: 5 days from parotid swelling onset (droplet precautions)
- Notification: statutory notification to local health protection team
- Warm/cold compresses to parotid area for comfort
Pharmacological
- Paracetamol/ibuprofen: for fever and pain
- Orchitis: bed rest, scrotal support, analgesia (NSAIDs), consider short course prednisolone (evidence limited)
- No specific antiviral treatment
- IV fluids: if unable to eat/drink due to pain or pancreatitis
Surgical/Interventional
- Not applicable for uncomplicated mumps
- Orchitis: rule out torsion with USS if diagnostic uncertainty
Referral Criteria
- Hospital admission: meningitis, encephalitis, severe orchitis, pancreatitis, dehydration
- Urology: orchitis with diagnostic uncertainty (exclude torsion)
- ENT: if parotid abscess suspected
- Public health: all cases (notification)
Prognosis
- Uncomplicated parotitis: full recovery in 7–10 days
- Orchitis: testicular atrophy in 30–50% of affected testes; infertility rare (~1%) due to usually unilateral involvement
- Meningitis: self-limiting, full recovery in most; rarely permanent sensorineural deafness
- Encephalitis: mortality <1% but neurological sequelae possible
- Deafness: 1 in 20,000; usually unilateral, permanent
- Pancreatitis: self-limiting; no evidence of increased diabetes risk
- MMR provides ~88% protection (waning immunity may explain outbreaks in young adults)
Other Relevant Information
Mumps Complications Summary
| Complication | Incidence | Notes |
|---|---|---|
| Parotitis | 70% of symptomatic | Bilateral in 70% |
| Orchitis | 20–30% (post-pubertal males) | Usually unilateral |
| Meningitis | ~10% | Self-limiting |
| Pancreatitis | ~5% | Raised amylase |
| Oophoritis | ~5% (post-pubertal females) | Fertility usually preserved |
| Encephalitis | ~0.1% | Serious, rare |
| Deafness | 1 in 20,000 | Unilateral, sensorineural |