Mumps (Child)

1. Clinical Overview

Summary

Mumps is an acute, highly contagious viral infection caused by the Mumps virus (genus Rubulavirus, family Paramyxoviridae), characterised clinically by painful, bilateral parotid gland swelling (epidemic parotitis). Prior to the introduction of the measles-mumps-rubella (MMR) vaccine in 1988, mumps was a ubiquitous childhood illness affecting 85-90% of individuals by age 15 years. [1,2] The incidence has declined by over 99% in countries with robust vaccination programmes, but outbreaks continue to occur in under-vaccinated populations, adolescents and young adults with waning immunity, and institutional settings (schools, universities, military barracks). [3,4]

While the parotitis is typically self-limiting, mumps is clinically significant due to its potential for serious complications, particularly in post-pubertal individuals. Orchitis occurs in 20-30% of post-pubertal males, aseptic meningitis in 10-15% of cases, pancreatitis in 4%, and permanent unilateral sensorineural deafness in approximately 1 in 20,000 cases. [5,6,7] Mumps is a notifiable disease in the United Kingdom and most developed nations, requiring laboratory confirmation and public health notification to enable outbreak control measures. [8]

The diagnosis is confirmed by oral fluid PCR (reverse transcription polymerase chain reaction detecting viral RNA), which has superseded serology as the gold-standard diagnostic test, particularly during the first week of illness. [9] Management is entirely supportive, focused on analgesia, hydration, and isolation for 5 days from symptom onset to prevent transmission. Post-exposure MMR vaccination does not prevent disease in exposed individuals already incubating the virus but is recommended to protect against future exposure. [10]

Key Facts

• Transmission: Respiratory droplet spread via coughing, sneezing, or talking; direct contact with infected saliva. Close contact is typically required (within 1 metre for prolonged periods).
• Incubation Period: 14-25 days (average 16-18 days). This prolonged incubation complicates outbreak control.
• Infectious Period: From 2 days before parotid swelling to 5 days after onset. Peak infectivity occurs just before and during early glandular swelling.
• Attack Rate: 60-90% in susceptible household contacts. [11]
• Subclinical Infection: 20-30% of infections are asymptomatic, yet these individuals remain infectious. [12]
• Immunity: Natural infection typically confers lifelong immunity. Vaccine-induced immunity may wane after 10-15 years, particularly after single-dose schedules.
• Seasonal Pattern: Historically peaks in late winter and spring (January-May in Northern Hemisphere), though this pattern is less pronounced in the vaccine era.

Clinical Pearls

The Sour Taste Test: Mumps parotitis pain is characteristically exacerbated by salivation. Offering the child a lemon wedge or sour sweet stimulates salivary flow and provokes intense pain at the angle of the jaw—a useful clinical sign to differentiate mumps from cervical lymphadenopathy.

Loss of the Mandibular Angle: Parotid gland enlargement obliterates the normal sharp angle of the mandible on palpation. If the jaw angle remains clearly palpable, consider lymphadenopathy (which sits below and medial to the mandible) rather than parotitis. This is the "Angle Sign"—its absence suggests mumps.

Orchitis Timing: In post-pubertal boys, testicular involvement typically occurs 4-8 days after parotid swelling, though it can occur without preceding parotitis in 10% of orchitis cases. Always warn adolescent males and parents to return urgently if scrotal pain develops. Unilateral involvement is more common (70%), but bilateral orchitis carries higher risk of testicular atrophy.

MMR is Not 100% Effective: Two doses of MMR vaccine are approximately 88% effective against mumps (compared to 95%+ for measles/rubella components). [13] Breakthrough infections occur, typically with milder disease and fewer complications. In outbreak settings, up to 30% of cases may be vaccinated individuals.

Amylase is Always Elevated: Serum amylase is universally elevated in mumps, originating from both salivary glands and (if involved) pancreas. However, amylase elevation is non-specific and occurs in many conditions. Use it to support, not confirm, diagnosis.

Silent CNS Involvement: CSF pleocytosis is demonstrable in up to 50% of mumps cases, even without clinical meningitis symptoms. [14] This reflects the virus's neurotropism and helps explain the high rate of asymptomatic CNS involvement.

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2. Epidemiology

Global Burden

Before widespread vaccination, mumps was endemic worldwide, with epidemics occurring every 2-5 years. An estimated 600,000 cases occurred annually in the United States alone prior to vaccine introduction. [15] Following implementation of routine MMR vaccination:

• USA: Incidence declined from 185,000 cases/year (pre-vaccine era, 1960s) to fewer than 300 cases/year by the 2000s—a > 99% reduction. However, resurgence occurred in the mid-2000s with multiple university outbreaks. [16]
• UK: Introduction of MMR in 1988 reduced annual notifications from 30,000-40,000 cases to fewer than 500 by the mid-1990s. A resurgence occurred between 2004-2005 (> 56,000 cases) among adolescents and young adults who missed MMR during the 1998 "Wakefield controversy" period of reduced vaccine uptake. [17,18]
• Australia: Similar dramatic reductions post-MMR introduction. Periodic outbreaks continue, particularly in high-density settings.

Age Distribution

Pre-vaccination era: Peak incidence occurred between ages 5-9 years, with most cases in children under 15 years.

Post-vaccination era: Bimodal distribution:

1. Unvaccinated young children (2-5 years) in communities with low vaccine uptake.
2. Adolescents and young adults (18-25 years) due to:
   • Waning vaccine immunity (particularly single-dose recipients)
   • The "Wakefield cohort" in the UK who missed MMR between 1998-2004
   • Congregate living settings (universities, military)

Risk Factors for Infection

• No MMR vaccination (most significant risk factor)
• Single-dose MMR only (insufficient protection; two doses required)
• Immunocompromise (reduced vaccine response)
• Close-contact settings: Schools, daycare centres, universities, dormitories, military barracks, sports teams
• Travel to endemic areas: Sub-Saharan Africa, South Asia, where vaccination coverage is incomplete
• Birth cohorts: In the UK, those born 1990-2000 have higher susceptibility due to variable MMR uptake during the Wakefield controversy

Geographical Patterns

• High-income countries with strong vaccination programmes: Sporadic cases and localised outbreaks predominate
• Countries with suboptimal vaccine coverage: Endemic transmission continues
• Orthodox religious communities (certain Jewish, Christian communities) have experienced outbreaks due to religious or philosophical vaccine objections

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3. Pathophysiology

Virology

Mumps virus is an enveloped, negative-sense, single-stranded RNA virus belonging to:

• Genus: Rubulavirus (along with parainfluenza viruses)
• Family: Paramyxoviridae

The viral genome encodes several proteins:

• Haemagglutinin-neuraminidase (HN): Mediates viral attachment and entry
• Fusion (F) protein: Enables viral envelope fusion with host cell membrane
• Nucleoprotein (N), Phosphoprotein (P), Large protein (L): Form the viral ribonucleoprotein complex

There is only one serotype of mumps virus, but 12 genotypes (A-N, excluding E and M) exist globally. Genotype distribution varies geographically and temporally. [19]

Pathogenesis: The Journey from Respiratory Tract to Glands

1. Entry and Primary Replication: Virus enters via respiratory droplets, depositing on the nasopharyngeal and upper respiratory epithelium. Initial viral replication occurs in the epithelial cells of the nasopharynx and regional (paratracheal and cervical) lymph nodes over 12-25 days (incubation period).

2. Primary Viraemia: Virus spreads via lymphatic drainage into the bloodstream, producing a primary viraemia around day 12-16 post-exposure. At this stage, the patient may develop non-specific prodromal symptoms (low-grade fever, malaise, myalgia).

3. Glandular and CNS Tropism: The virus exhibits marked tropism for:

   • Glandular tissue: Parotid and other salivary glands (submandibular, sublingual), pancreas, testes, ovaries, thyroid, thymus, breasts
   • Central nervous system: Meninges, choroid plexus, ependymal lining
   • Other sites: Myocardium, kidneys, joints

4. Parotitis: Viral replication within parotid acinar cells causes:

   • Direct cytopathic damage to glandular epithelium
   • Inflammatory infiltration: Lymphocytes, macrophages, and neutrophils invade the gland
   • Ductal obstruction: Inspissated secretions and cellular debris block Stensen's duct
   • Oedema and swelling: Parotid gland is encased in a dense fibrous capsule, so swelling produces intense pain due to capsular stretch

5. Immune Response:

   • Innate immunity: Type I interferons (IFN-α/β) are produced early, limiting viral spread
   • Humoral immunity: IgM antibodies appear within 5 days of parotitis onset; IgG antibodies appear shortly thereafter and persist for life
   • Cell-mediated immunity: CD8+ T-cells clear infected cells; CD4+ T-cells orchestrate the response
   • Immune-mediated complications: Some manifestations (e.g., orchitis, oophoritis) may involve immune complex deposition and inflammatory damage beyond direct viral cytopathology

6. Viral Shedding: Virus is shed in saliva from 7 days before to 9 days after parotitis onset, with peak shedding coinciding with glandular swelling. Viral RNA can be detected in urine, and in cases of meningitis, in CSF.

Molecular Mechanisms of Complications

Orchitis: Post-pubertal testes have completed spermatogenesis and developed tight junctions in the seminiferous tubules. Viral invasion triggers:

• Intense interstitial oedema within the tunica albuginea (dense, non-expandable capsule), causing severe pain and ischaemia
• Autoimmune reaction: Breakdown of blood-testis barrier exposes sperm antigens, potentially generating anti-sperm antibodies (though clinical significance remains debated)
• Testicular atrophy occurs in 30-50% of orchitis cases, typically developing 1-2 months post-infection

Aseptic Meningitis: Direct viral invasion of the meninges and CSF. CSF shows lymphocytic pleocytosis, mildly elevated protein, and normal glucose (unlike bacterial meningitis). Viral RNA detectable by PCR.

Pancreatitis: Viral tropism for pancreatic acinar and ductal cells. Typically mild and self-limiting, though rare cases of severe haemorrhagic pancreatitis occur.

Sensorineural Hearing Loss: Mumps virus invades the cochlea and vestibular apparatus via haematogenous spread or through the cochlear aqueduct from CSF. Damage to the organ of Corti causes irreversible hearing loss, usually unilateral and sudden. The endolymphatic hydrops theory suggests inflammatory blockage of the endolymphatic duct contributes. [20]

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4. Clinical Presentation

History

Incubation Period (14-25 days)

The patient is asymptomatic. Parents may recall exposure to a mumps case at school or within the household 2-3 weeks prior.

Prodromal Phase (1-2 days before parotitis)

• Non-specific symptoms: Low-grade fever (37.5-38.5°C), malaise, headache, myalgia, anorexia
• Early pain: Some children report earache or discomfort at the angle of the jaw before visible swelling appears
• Many cases have no prodrome, with parotid swelling as the presenting feature

Parotitis Phase (Days 0-7)

Onset: Typically sudden. Parent reports child woke with "chipmunk cheeks" or "hamster face".

Pain:

• Severe, aching pain at the angle of the jaw (site of parotid gland)
• Pain worsens with jaw movement (chewing, talking), salivation (especially with sour or acidic foods), and pressure over the gland
• Earache is common (referred pain along the auriculotemporal nerve)

Swelling:

• Begins unilateral in 75% of cases, becoming bilateral within 1-2 days in 70% of cases
• Starts anterior and inferior to the ear lobe, extending down to the angle of the mandible and forward towards the chin
• The ear lobe is pushed upward and outward
• Swelling peaks on days 2-3, then gradually resolves over 7-10 days
• In 30% of cases, swelling remains unilateral throughout

Associated symptoms:

• Fever: 38-40°C, typically lasting 3-4 days
• Difficulty chewing and swallowing: Due to pain, trismus, and mechanical obstruction
• Dry mouth: Reduced salivary flow due to ductal obstruction
• Trismus: Mild to moderate limitation of jaw opening (not as severe as in peritonsillar abscess)

Other salivary glands:

• Submandibular glands: Involved in 10% of cases, causing swelling beneath the jaw
• Sublingual glands: Rare; swelling of the floor of mouth
• Isolated submandibular or sublingual involvement without parotitis can occur (5% of cases)

Subclinical Infection (20-30%)

Up to one-third of mumps infections are asymptomatic or present with only non-specific respiratory symptoms, yet remain infectious. This silent transmission complicates outbreak control.

Other Systemic Manifestations

Orchitis (20-30% of post-pubertal males)

• Timing: Typically 4-8 days after parotitis onset (range 1-21 days). Can occur without preceding parotitis in 10% of cases.
• Presentation: Sudden onset of severe testicular pain, swelling, erythema, and warmth of the hemiscrotum
• Fever: High fever (39-40°C) accompanies orchitis
• Unilateral in 70%, bilateral in 30%
• Pre-pubertal boys: Orchitis is rare (less than 1%), as the pre-pubertal testis has undeveloped seminiferous tubules with incomplete blood-testis barrier

Oophoritis (5% of post-pubertal females)

• Lower abdominal or pelvic pain, typically unilateral
• Difficult to diagnose clinically; often a diagnosis of exclusion
• Does not impair fertility (unlike orchitis, ovarian reserve is unaffected)

Aseptic Meningitis (10-15%)

• Headache: Severe, generalised, worse on movement
• Neck stiffness, photophobia, vomiting
• Altered consciousness: Lethargy, irritability (especially in young children)
• Symptoms typically appear 3-10 days after parotitis, but may precede it or occur without parotitis
• CSF findings: Lymphocytic pleocytosis (10-2000 cells/mm³, predominantly lymphocytes), mildly elevated protein (0.5-1.0 g/L), normal glucose, and no organisms on Gram stain
• Mumps is historically one of the most common causes of aseptic meningitis in the pre-vaccine era

Encephalitis (less than 1%)

• Rarer and more severe than meningitis
• Altered consciousness, seizures, focal neurological signs (hemiparesis, ataxia, cranial nerve palsies)
• Mortality ~1%; neurological sequelae in 25% of survivors
• May occur without parotitis

Pancreatitis (4%)

• Epigastric pain, often severe, radiating to the back
• Nausea and vomiting
• Elevated serum amylase and lipase (though amylase is elevated in mumps even without pancreatitis due to salivary origin)
• Usually mild and self-limiting; resolves in 1 week

Myocarditis (less than 1%)

• Rare but described in case reports
• ECG changes, arrhythmias, cardiac failure
• Usually mild and self-limiting

Thyroiditis, Mastitis, Nephritis

• All rare; case reports exist

Sensorineural Hearing Loss (1 in 20,000)

• Sudden onset unilateral deafness, often noticed 4-5 days after parotitis
• May be accompanied by tinnitus and vertigo
• Permanent in most cases
• Transient hearing loss occurs more frequently (4% of cases)

Pregnancy Complications

• First trimester infection: Associated with spontaneous abortion in up to 27% of cases [21]
• No congenital mumps syndrome: Unlike rubella, mumps does not cause congenital malformations
• Rare reports of endocardial fibroelastosis in infants born to mothers with first-trimester mumps, but causality not established

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5. Clinical Examination

General Appearance

• Child appears uncomfortable and in pain, often holding hand to jaw
• Facial asymmetry: Swelling obliterates normal facial contours
• "Hamster face" or "Chipmunk cheeks": Descriptive appearance
• Trismus: Mild limitation of mouth opening due to pain, though jaw can still open (unlike peritonsillar abscess)

Head and Neck Examination

Parotid Gland Inspection

• Swelling: Diffuse, smooth, non-fluctuant swelling anterior and inferior to the ear
• Extends from the zygomatic arch superiorly to the angle of the mandible inferiorly, and from the ear posteriorly to the midline of the cheek anteriorly
• Ear lobe displacement: The ear lobe is pushed upward and outward—a hallmark sign
• Obliteration of the mandibular angle: The normally sharp angle of the jaw is no longer palpable (the "Angle Sign")
• Skin: Normal colour and texture (no erythema, unlike bacterial parotitis)

Parotid Gland Palpation

• Tenderness: Moderate to severe tenderness over the gland
• Consistency: Firm, boggy, non-fluctuant (no pus)
• Temperature: Warm but not hot (unlike bacterial infection)

Intraoral Examination

• Stensen's duct orifice: Located on the buccal mucosa opposite the second upper molar. In mumps, the orifice may appear:
  • Red and swollen
  • No purulent discharge (contrast with bacterial parotitis, where pus can be expressed)
• Difficulty opening mouth fully due to pain and trismus

Other Salivary Glands

• Palpate submandibular glands (beneath the horizontal ramus of the mandible): may be enlarged and tender
• Sublingual glands (floor of mouth): rarely involved

Cervical Lymph Nodes

• Usually not significantly enlarged (helps differentiate from lymphadenitis)
• If prominent cervical nodes present, consider EBV, CMV, or bacterial lymphadenitis instead

Systemic Examination

Neurological Examination

• Meningism: Assess for neck stiffness (Kernig's sign, Brudzinski's sign), photophobia
• Consciousness level: GCS, AVPU
• Cranial nerves: Especially VII (facial nerve, which runs through the parotid—rarely affected in mumps, unlike in parotid tumours)
• Fundoscopy: Papilloedema (raised ICP)

Genitourinary Examination (in adolescent/post-pubertal males)

• Scrotum: Inspect for swelling, erythema
• Testicular palpation: Enlarged, tender, firm testis; loss of cremasteric reflex if severe swelling
• Prehn's sign: Elevation of the scrotum may provide relief (suggestive of orchitis/epididymitis) vs. worsening pain in testicular torsion (surgical emergency differential)
• Always examine both testes and document size

Abdominal Examination

• Epigastric tenderness: Suggests pancreatitis
• Assess hydration status (mucous membranes, skin turgor, capillary refill time)

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6. Differential Diagnosis

Mumps parotitis has a relatively characteristic presentation, but several conditions can mimic it:

1. Bacterial Parotitis (Suppurative Parotitis)

Key differentiator: In bacterial parotitis, pus can usually be expressed from Stensen's duct by massaging the gland externally—this does not occur in mumps.

2. Cervical Lymphadenitis

• Swelling is below and posterior to the angle of the mandible (lymph nodes sit separate from the parotid)
• Mandibular angle remains palpable (not obliterated)
• Often associated with pharyngitis, dental infection, or scalp infection (occipital nodes)
• Multiple discrete, mobile, tender lymph nodes palpable (vs. diffuse glandular swelling in mumps)

3. Salivary Calculus (Sialolithiasis)

• Unilateral swelling, sudden onset with meals (stimulation of saliva)
• Painful, but pain is intermittent and related to eating
• Submandibular gland more commonly affected than parotid (80% vs. 20%)
• Bimanual palpation may reveal a hard, palpable stone in the duct
• Absence of fever (unless secondarily infected)
• Imaging (ultrasound, sialography, CT) demonstrates calculus

4. Epstein-Barr Virus (EBV) Infectious Mononucleosis

• Generalised lymphadenopathy (anterior and posterior cervical, axillary, inguinal)
• Pharyngitis: Severe tonsillar enlargement with exudate
• Splenomegaly, hepatomegaly
• Fatigue out of proportion to fever
• Monospot test positive, atypical lymphocytes on blood film
• Parotid gland usually not involved (though submandibular lymphadenopathy can mimic parotitis)

5. Cytomegalovirus (CMV)

• Similar to EBV but monospot negative
• More common in immunocompromised
• Serology (CMV IgM) or PCR confirms

6. HIV Primary Infection (Acute Retroviral Syndrome)

• Parotid swelling can occur in acute HIV seroconversion or chronic HIV (HIV-associated salivary gland disease)
• Associated with fever, rash, lymphadenopathy, pharyngitis
• Risk factors: Unprotected sexual contact, IVDU
• HIV serology (p24 antigen, HIV RNA) confirms

7. Recurrent Parotitis of Childhood

• Recurrent episodes of unilateral (rarely bilateral) parotid swelling
• Each episode lasts 2-7 days; recurs every few weeks to months
• Aetiology unclear: Autoimmune, congenital ductal abnormalities, sialectasis
• Diagnosis of exclusion: Requires ultrasound (shows sialectasis—dilated ducts with punctate sialectasis)
• Typically resolves by puberty

8. Autoimmune Conditions

Sjögren Syndrome (Juvenile): Rare in children. Chronic bilateral parotid swelling, dry eyes (keratoconjunctivitis sicca), dry mouth. Anti-Ro/La antibodies positive.

Sarcoidosis: Bilateral parotid swelling, uveitis, fever. Rare in children. Elevated ACE, non-caseating granulomas on biopsy.

9. Neoplasm

• Unilateral, painless, firm, slowly progressive swelling
• Facial nerve palsy (if malignant)
• Imaging (MRI) and biopsy needed
• Rare in children (80% of parotid tumours in children are benign: pleomorphic adenoma, haemangioma)

10. Other Viral Causes of Parotitis

• Parainfluenza viruses (types 1 and 3)
• Influenza A virus
• Coxsackievirus
• Adenovirus
• All can cause parotitis, but less commonly than mumps in unvaccinated populations

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7. Investigations

Diagnostic Approach

Mumps is a notifiable disease in the UK and most countries. Laboratory confirmation is mandatory for public health surveillance, outbreak investigation, and to differentiate from other causes of parotitis.

Microbiology (First-Line)

1. Oral Fluid RT-PCR (Gold Standard)

Specimen: Oral fluid (saliva) collected using a Virological Swab (Virocult swab) or Oracol device (specially designed sponge swab).

Technique:

• Rub the swab gently over the gums and inner cheeks for 30-60 seconds to collect saliva and buccal cells
• Swab should be taken within the first 5 days of parotitis onset for optimal sensitivity (viral shedding peaks early)
• Place swab in viral transport medium and send to virology laboratory

Sensitivity:

• 80-90% if collected within first 5 days
• Sensitivity declines after day 5 as viral shedding decreases

Specificity: > 95% (highly specific for mumps virus RNA)

Detection: Reverse transcription PCR (RT-PCR) detects mumps virus RNA. Cycle threshold (Ct) values less than 30 indicate high viral load.

Genotyping: PCR can identify the mumps virus genotype (A-N), useful for outbreak investigation and tracking transmission chains.

Advantages:

• Non-invasive (especially important in children)
• Detects virus early in illness
• Can differentiate wild-type virus from vaccine strain

2. Serology (IgM and IgG)

Specimen: Venous blood for serum

IgM Antibodies:

• Appear within 5 days of parotitis onset
• Peak at 1 week, then decline over 6-12 weeks
• Sensitivity: 70-80% (lower than PCR, especially in vaccinated individuals who mount a rapid IgG response and minimal IgM)
• False negatives: Common in vaccinated individuals (rapid anamnestic IgG response without IgM rise)
• False positives: Cross-reactivity with other paramyxoviruses (parainfluenza)

IgG Antibodies:

• Appear within 7-10 days of parotitis onset
• Persist for life
• Acute and convalescent serology: A four-fold rise in IgG between acute (within 5 days) and convalescent (2-3 weeks later) sera confirms acute infection
• Single positive IgG indicates past infection or vaccination, not acute infection

When to use serology:

• If oral fluid swab negative but clinical suspicion remains high
• Late presentation (> 7 days after onset, when viral shedding has declined)
• Outbreak investigation to confirm immunity in contacts

Limitations:

• Lower sensitivity than PCR, especially in vaccinated individuals
• Cannot distinguish vaccine strain from wild-type virus

3. Other Specimens (Specialist Use)

Urine RT-PCR: Mumps virus is shed in urine. Can be used if oral fluid not available, though less sensitive.

CSF RT-PCR: In cases of aseptic meningitis or encephalitis. Confirms mumps as the causative agent. CSF shows lymphocytic pleocytosis, elevated protein, normal glucose.

Throat Swab: Less sensitive than oral fluid; not routinely recommended.

Biochemical Tests

Serum Amylase

• Always elevated in mumps, even without pancreatitis
• Origin: Salivary-type amylase (S-amylase) from parotid gland; pancreatic-type amylase (P-amylase) if pancreatitis present
• Degree of elevation does not correlate with severity
• Non-specific: Elevated in many conditions (pancreatitis of any cause, salivary duct obstruction, ectopic pregnancy, diabetic ketoacidosis, renal failure)

Utility: Supports diagnosis but cannot confirm it. Must be interpreted alongside clinical picture and virology.

Serum Lipase

• More specific for pancreatitis than amylase
• Elevated if pancreatic involvement (mumps pancreatitis)
• Remains elevated longer than amylase

Full Blood Count (FBC)

• White Cell Count: Normal or mildly elevated (viral infections typically do not cause marked leucocytosis)
• Lymphopenia may occur early; lymphocytosis later
• Non-specific: Not diagnostic

C-Reactive Protein (CRP)

• Normal or mildly elevated (unlike bacterial infections where CRP is markedly elevated)
• Useful to differentiate mumps from bacterial parotitis

Imaging

Ultrasound of Parotid Gland

Indications:

• Uncertainty about diagnosis (atypical presentation)
• Suspicion of abscess (bacterial parotitis)
• To rule out salivary calculus

Findings in mumps:

• Diffuse enlargement of the parotid gland
• Hypoechoic (dark) appearance due to oedema
• Increased vascularity on Doppler (inflammation)
• No focal abscess or calculus

Findings in bacterial parotitis:

• Focal hypoechoic or anechoic collection (abscess)
• Pus with internal echoes

CT/MRI

• Rarely needed
• Reserved for suspected complications (abscess, neoplasm)

Lumbar Puncture (if meningitis suspected)

Indications:

• Clinical signs of meningism (neck stiffness, headache, photophobia, altered consciousness)
• To exclude bacterial meningitis (cannot be distinguished clinically)

CSF findings in mumps aseptic meningitis:

• Opening pressure: Normal or mildly elevated
• Appearance: Clear (unlike bacterial meningitis, which is turbid)
• White cell count: 10-2000 cells/mm³ (predominantly lymphocytes, though neutrophils may predominate early)
• Protein: Mildly elevated (0.5-1.0 g/L; normal less than 0.45 g/L)
• Glucose: Normal (> 60% of blood glucose; CSF:serum glucose ratio > 0.5)
  • "Key differentiator: Bacterial meningitis has low glucose (less than 2.2 mmol/L or less than 50% of blood glucose)"
• Gram stain: No organisms seen
• CSF culture: Sterile (no bacterial growth)
• CSF mumps RT-PCR: Positive for mumps virus RNA (confirms diagnosis)

Public Health Notification

UK (UKHSA - UK Health Security Agency):

• Mumps is a notifiable disease under the Health Protection (Notification) Regulations 2010
• Clinicians must notify the local Health Protection Team (HPT) or Consultant in Communicable Disease Control (CCDC) within 3 days of suspicion (do not wait for laboratory confirmation)
• Notification enables:
  • Outbreak investigation
  • Contact tracing
  • Vaccination of susceptible contacts
  • School/workplace exclusion advice
  • National surveillance

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8. Management

General Principles

There is no specific antiviral therapy for mumps. Management is entirely supportive, focused on:

1. Symptom relief (analgesia, hydration)
2. Isolation to prevent transmission
3. Monitoring for complications
4. Public health measures (notification, contact tracing)

Isolation and Exclusion

Rationale: Mumps is highly infectious via respiratory droplets. Infected individuals must be isolated to prevent transmission.

Infectious period: From 2 days before parotid swelling to 5 days after onset.

Exclusion from school/childcare/work:

• 5 days from onset of parotitis
• PHE/UKHSA guidance: "Exclude for 5 days from onset of swelling"
• Healthcare workers: Exclude for 5 days; must not work in high-risk areas (immunocompromised patients, neonates)

Household contacts:

• Do not need to be excluded if asymptomatic
• Check MMR vaccination status; offer catch-up MMR if unvaccinated (though this will not prevent disease if already incubating, it protects against future exposure)

Supportive Care

1. Analgesia and Antipyretics

First-line: Paracetamol (acetaminophen)

• Dose: 15 mg/kg every 4-6 hours (max 4 doses/24 hours; max 1 g per dose in children > 12 years)
• Effective for pain and fever

Second-line: Ibuprofen (NSAID)

• Dose: 5-10 mg/kg every 6-8 hours (max 400 mg per dose in children > 12 years)
• Anti-inflammatory effect may help reduce parotid swelling and pain
• Caution: Avoid in dehydration, renal impairment, suspected pancreatitis (theoretical risk of worsening, though evidence weak)

Avoid: Aspirin in children (less than 16 years) due to risk of Reye's syndrome

Topical measures:

• Warm or cold compresses to the parotid area (whichever provides relief)
• Some children prefer cold (ice packs wrapped in towel); others prefer warmth

2. Hydration

• Encourage oral fluids to maintain hydration
• Avoid acidic or sour drinks (orange juice, lemonade) as these stimulate painful salivation
• Offer:
  • Water
  • Milk
  • Neutral-pH fluids
• Soft, bland diet (avoid foods requiring excessive chewing)

Intravenous fluids: If child unable to tolerate oral fluids due to pain or vomiting (e.g., if pancreatitis or meningitis present)

3. Oral Hygiene

• Maintain oral hygiene (gentle tooth brushing) to prevent secondary bacterial parotitis
• Avoid mouthwashes containing alcohol (painful on inflamed mucosa)

Management of Complications

Orchitis

Assessment:

• Examine scrotum: size, symmetry, colour, tenderness
• Doppler ultrasound if diagnostic uncertainty (to exclude testicular torsion—surgical emergency)

Management:

• Analgesia: NSAIDs (ibuprofen) + paracetamol. May require opioids (codeine, morphine) in severe cases
• Scrotal support: Tight-fitting underwear or scrotal support (elevates testis, reduces pain)
• Ice packs: Applied to scrotum (wrapped in towel to avoid frostbite), 15 minutes on, 15 minutes off
• Bed rest: For first 2-3 days
• Reassurance: Inform patient/parents that:
  • Symptoms resolve in 1-2 weeks
  • Sterility is rare (occurs in less than 1% of cases, usually only if bilateral and severe)
  • Testicular atrophy may occur in 30-50% of affected testes, but fertility usually preserved

Corticosteroids: Historically used (to reduce inflammation and theoretically prevent atrophy), but no RCT evidence of benefit. Not routinely recommended. [22]

Follow-up: Review in 2-3 months to assess for testicular atrophy (ultrasound if uncertainty)

Aseptic Meningitis

Assessment:

• Lumbar puncture: To confirm diagnosis and exclude bacterial meningitis (see Investigations section for CSF findings)
• Neuroimaging (CT/MRI): Not routinely required unless focal neurological signs, reduced GCS, or suspicion of raised ICP

Management:

• Admission: For observation, IV fluids, and analgesia (if severe headache/vomiting)
• Analgesia: Paracetamol, NSAIDs; opioids if needed
• Antiemetics: Ondansetron, cyclizine for nausea/vomiting
• IV fluids: If unable to tolerate oral intake
• Reassurance: Mumps aseptic meningitis is almost always benign and self-limiting. Symptoms resolve in 7-10 days without sequelae in > 95% of cases.

Antibiotics: Not indicated (viral aetiology). However, if bacterial meningitis cannot be excluded (e.g., LP not yet performed or CSF results pending), empirical IV antibiotics (ceftriaxone or cefotaxime) must be started immediately and discontinued once bacterial meningitis excluded.

Encephalitis

Presentation: Altered consciousness, seizures, focal neurology

Management:

• Urgent admission to paediatric intensive care unit (PICU)
• Neuroimaging (MRI brain)
• Supportive care: Airway protection, IV fluids, seizure control (benzodiazepines, phenytoin)
• No specific antiviral: Mumps virus does not respond to aciclovir (unlike HSV encephalitis)
• Prognosis: Mortality ~1%; neurological sequelae (cognitive impairment, motor deficits) in 25% of survivors

Pancreatitis

Assessment:

• Serum amylase and lipase: Markedly elevated
• Ultrasound abdomen: Exclude gallstones, assess pancreatic oedema
• Blood glucose: Monitor (pancreatic inflammation can cause transient hyperglycaemia or hypoglycaemia)

Management:

• Nil by mouth (NBM) initially, to rest the pancreas
• IV fluids: Aggressive hydration (key to preventing pancreatic necrosis in severe pancreatitis)
• Analgesia: Opioids (morphine)
• Antiemetics: Ondansetron
• Monitor: Amylase/lipase daily, FBC, CRP, renal function, calcium, glucose
• Reintroduce oral feeding: Gradually, once pain and vomiting settled (typically 24-48 hours in mumps pancreatitis, which is usually mild)

Prognosis: Mumps pancreatitis is usually mild and self-limiting. Resolves in 7 days. Progression to chronic pancreatitis or diabetes is extremely rare.

Hearing Loss

Presentation: Parent or child reports sudden hearing loss (usually unilateral), tinnitus, vertigo

Assessment:

• Otoscopy: Normal external auditory canal and tympanic membrane (excludes conductive hearing loss)
• Rinne and Weber tests: Sensorineural loss (Rinne positive, Weber lateralises to normal ear)
• Pure tone audiometry: Confirms sensorineural hearing loss; quantifies degree (mild, moderate, severe, profound)

Management:

• Urgent ENT referral
• High-dose oral corticosteroids: Prednisolone 1 mg/kg/day for 7 days, then taper. Evidence is limited, but often trialled if presenting within 72 hours of onset (theory: reduce cochlear inflammation). [23]
• Hearing aid: If permanent hearing loss confirmed on repeat audiometry at 3 months
• Cochlear implant: For profound bilateral sensorineural hearing loss (rare)

Prognosis: Permanent unilateral hearing loss in 1 in 20,000 mumps cases. Transient hearing loss (resolves within weeks) in ~4% of cases.

Public Health Measures

Notification

• Notify local Health Protection Team (HPT) or CCDC within 3 days of suspicion (statutory requirement in UK)
• Provide:
  • Patient demographics
  • Clinical details (date of onset, symptoms)
  • Vaccination history (number of MMR doses, dates)
  • Possible exposure source (recent travel, contact with known mumps case)

Contact Tracing

HPT will:

• Identify close contacts (household members, school/daycare attendees, healthcare workers)
• Check MMR vaccination status of contacts
• Offer catch-up MMR to unvaccinated or incompletely vaccinated contacts

Post-exposure MMR:

• Does NOT prevent disease in contacts already incubating mumps (incubation period 14-25 days; vaccine takes 2-3 weeks to induce immunity)
• Protects against future exposure (mumps often occurs in waves during outbreaks)
• Safe to give to contacts even if they develop mumps subsequently

Outbreak Control

In outbreak settings (schools, universities):

• Mass MMR vaccination campaigns for unvaccinated/single-dose individuals
• Exclusion policies: Infected individuals excluded for 5 days
• Enhanced surveillance: Active case finding
• Communication: Parents/students informed of outbreak, encouraged to report symptoms early

Role of MMR Vaccination

Routine Immunisation Schedule (UK):

• First dose: 12-13 months of age
• Second dose: 3 years 4 months (pre-school booster)

Catch-up vaccination:

• Offer to any child/adult with less than 2 documented MMR doses, at any age
• No upper age limit for catch-up
• Particularly important for:
  • Adolescents born 1990-2000 (Wakefield cohort)
  • University students
  • Healthcare workers

MMR Vaccine Efficacy:

• One dose: ~78% protection against mumps (lower than for measles/rubella)
• Two doses: ~88% protection [13]
• Vaccine-induced immunity wanes over time (particularly after 10-15 years), hence breakthrough infections in young adults despite 2 doses

Contraindications to MMR:

• Severe immunosuppression: HIV with CD4 less than 200, chemotherapy, high-dose steroids (> 2 mg/kg/day prednisolone for > 1 week), biological agents
• Pregnancy: MMR is a live vaccine; avoid in pregnancy (though inadvertent vaccination in pregnancy has not been shown to harm the foetus)
• Anaphylaxis to previous MMR dose or vaccine components (gelatin, neomycin)
• Recent immunoglobulin (wait 3 months)

NOT contraindications:

• Egg allergy (MMR is grown on chick embryo fibroblasts, not egg, and safe in egg allergy)
• Breastfeeding
• Immunocompetent individuals with household contacts who are immunosuppressed (vaccine virus not transmissible)

Antiviral Therapy?

No antiviral agents are effective against mumps virus. Ribavirin has been investigated in vitro but has no clinical role.

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9. Complications

Early Complications (During Acute Illness)

Late Complications

Sensorineural Hearing Loss

• Incidence: Permanent unilateral deafness in ~1 in 20,000 cases; transient hearing loss in ~4% [20]
• Mechanism: Viral invasion of cochlea and organ of Corti; endolymphatic hydrops
• Presentation: Sudden hearing loss, tinnitus, vertigo, typically 4-5 days after parotitis
• Management: Urgent ENT referral; high-dose corticosteroids if presenting within 72 hours; hearing aid if permanent loss
• Prognosis: Permanent in most cases; usually unilateral (bilateral profound deafness extremely rare)

Testicular Atrophy and Fertility

• Incidence: Atrophy occurs in 30-50% of orchitis cases [24]
• Timeline: Develops 1-2 months post-orchitis
• Mechanism: Ischaemia (pressure necrosis within tunica albuginea) and autoimmune damage
• Fertility impact:
  • "Unilateral atrophy: Fertility usually preserved (contralateral testis compensates)"
  • "Bilateral atrophy: Risk of subfertility, but complete sterility rare (less than 1% of all mumps cases)"
• Counselling: Reassure that fertility is usually maintained; consider sperm banking in bilateral severe orchitis (rare)

Pregnancy Complications

• First trimester infection: Spontaneous abortion in up to 27% of cases [21]
• No congenital malformations: Unlike rubella, mumps does not cause congenital mumps syndrome
• Endocardial fibroelastosis: Rare case reports suggest association, but causality not proven

Association with Type 1 Diabetes?

• Historical hypothesis: Mumps infection may trigger autoimmune destruction of pancreatic beta cells (type 1 diabetes)
• Current evidence: No definitive causal link established. Large epidemiological studies have not confirmed increased T1DM risk post-mumps. [25]

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10. Prognosis and Outcomes

Uncomplicated Mumps

• Parotitis: Resolves in 7-10 days without treatment
• Fever: Settles in 3-4 days
• Pain: Improves significantly by day 5
• Return to school: After 5 days from onset of swelling
• Full recovery: Expected in 2 weeks

Immunity

• Lifelong immunity after natural infection (reinfection extremely rare)
• Second episodes of "mumps-like illness" are almost always due to other viruses (parainfluenza, EBV, CMV) or non-infectious causes (recurrent parotitis of childhood)

Complicated Mumps

• Orchitis: Symptoms resolve in 1-2 weeks. Testicular atrophy may develop over 1-2 months. Fertility usually preserved.
• Aseptic meningitis: Symptoms resolve in 7-10 days. Long-term sequelae rare (less than 1%).
• Encephalitis: Mortality ~1%. Neurological sequelae (cognitive, motor deficits) in 25% of survivors.
• Pancreatitis: Resolves in 1 week. Chronic pancreatitis extremely rare.
• Hearing loss: Permanent unilateral deafness in ~1 in 20,000. Adaptation usually good with unilateral loss; hearing aid if needed.

Mortality

• Overall mortality: less than 1 per 10,000 cases in developed countries
• Causes of death: Encephalitis (most common), myocarditis, severe pancreatitis
• Pre-vaccine era: 30-50 deaths/year in USA (population ~300 million)
• Post-vaccine era: less than 5 deaths/year in USA

Long-Term Outcomes

• Neurological: Rare long-term sequelae from encephalitis (cognitive impairment, epilepsy, motor deficits) in less than 1% of cases
• Fertility: Preserved in > 99% of cases (even after unilateral orchitis)
• Hearing: Permanent unilateral hearing loss in ~1 in 20,000; bilateral profound deafness extremely rare
• Quality of life: Excellent in vast majority; complications rare and usually self-limiting

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11. Prevention

Primary Prevention: MMR Vaccination

Vaccine: Live attenuated mumps virus vaccine (Jeryl Lynn strain or Rubini strain), combined with measles and rubella (MMR)

Schedule (UK):

• First dose: 12-13 months
• Second dose: 3 years 4 months (pre-school booster)

Efficacy:

• One dose: ~78% protection against mumps clinical disease
• Two doses: ~88% protection [13]
• Lower than for measles (97%) or rubella (97%) components
• Waning immunity over 10-15 years contributes to breakthrough infections in young adults

Safety:

• Excellent safety profile
• Common side effects: Fever (5-10%), rash (5%), mild parotid swelling (1%), transient joint pain in adults (25%, mainly rubella component)
• Serious adverse events: Febrile seizures (1 in 3000 doses, same risk as natural measles), thrombocytopenia (1 in 30,000), anaphylaxis (1 in 1 million)
• MMR and autism: The Wakefield 1998 paper claiming a link between MMR and autism was fraudulent and has been retracted. Extensive subsequent research has conclusively shown no link between MMR and autism. [26,27]

Contraindications:

• Severe immunosuppression
• Pregnancy
• Anaphylaxis to previous dose or vaccine components

Catch-up:

• Offer to anyone with less than 2 documented doses, at any age
• Particularly target:
  • Adolescents and young adults (18-25 years) who missed doses during Wakefield controversy
  • Healthcare workers
  • Travellers to endemic areas

Secondary Prevention: Post-Exposure Prophylaxis

MMR vaccine after exposure:

• Does NOT prevent disease in exposed individuals already incubating (incubation 14-25 days; vaccine takes 2-3 weeks to work)
• Protects against future exposure (important in outbreak settings)
• Safe to give even if individual develops mumps

Immunoglobulin (IVIG or NHIG):

• Not effective for mumps post-exposure prophylaxis (unlike for measles or hepatitis A)
• No role in mumps prevention or treatment

Infection Control in Healthcare Settings

Healthcare workers (HCWs):

• All HCWs should have documented evidence of 2 MMR doses or serological evidence of immunity
• Unvaccinated HCWs exposed to mumps: Exclude from work for 26 days post-exposure (longest incubation period)
• Infected HCWs: Exclude for 5 days from onset of swelling

Hospitalised mumps patients:

• Respiratory isolation: Single room, droplet precautions
• Cohort patients if multiple mumps cases (place in same bay)
• Duration of isolation: 5 days from onset of swelling

Contact tracing in hospitals:

• Identify staff and patients exposed (within 1 metre for > 15 minutes)
• Check vaccination status; offer MMR if less than 2 doses

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12. Evidence and Guidelines

Key Guidelines

Landmark Studies and Knowledge

1. MMR and Autism Controversy (Wakefield, 1998)

Event: Andrew Wakefield published a paper in The Lancet claiming a link between MMR vaccine and autism and inflammatory bowel disease, based on 12 children. [31]

Impact:

• Media panic; MMR uptake in UK dropped from 92% (1996) to 80% (2003)
• Resurgence of measles, mumps, and rubella
• Mumps outbreaks in 2004-2005 (> 56,000 cases) affected the "Wakefield cohort"—those born 1990-2000 who missed MMR

Outcome:

• Wakefield's study was fraudulent (conflicts of interest, data manipulation, unethical practices)
• Retracted by The Lancet in 2010
• Wakefield struck off the UK medical register
• Numerous large studies (> 1 million children) have found no link between MMR and autism [26,27]

Legacy: Ongoing vaccine hesitancy; importance of public health communication

2. Mumps Outbreaks in Vaccinated Populations

Key observation: Despite high two-dose MMR coverage, mumps outbreaks continue in universities, military, and other congregate settings. [3,4]

Reasons:

• Waning immunity: Vaccine-induced antibodies decline over 10-15 years
• Lower vaccine efficacy for mumps (~88%) compared to measles/rubella (~97%)
• High transmission intensity in congregate settings overcomes vaccine protection

Response:

• Some countries (USA in outbreak settings) have considered third MMR dose for high-risk groups; evidence of benefit unclear [32]
• Reinforces importance of two-dose schedule and catch-up vaccination

3. Mumps Vaccine Strain Evolution

Strains used:

• Jeryl Lynn: USA, UK; most effective strain
• Rubini: Used in some countries; withdrawn due to low efficacy
• Urabe: Japan, some European countries; more effective but higher rate of aseptic meningitis (withdrawn in UK)

Current UK vaccine: MMR VaxPRO (Sanofi Pasteur) contains Jeryl Lynn mumps strain

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13. Patient and Layperson Explanation

What is Mumps?

Mumps is a viral infection that causes the glands in your cheeks (called the parotid glands) to swell up, giving a "hamster face" or "chipmunk cheeks" appearance. It is caused by a virus and spreads through coughs, sneezes, and saliva.

Is it Serious?

For most children, mumps is just painful and uncomfortable. The swelling goes down in about a week, and you feel better. However, mumps can sometimes cause complications:

• In teenage boys and men: The virus can spread to the testicles (called orchitis), causing severe pain and swelling. This is very painful but rarely causes infertility.
• Meningitis: The virus can cause inflammation around the brain, leading to severe headache and neck stiffness. This usually gets better on its own.
• Deafness: Rarely (about 1 in 20,000 cases), mumps can cause permanent hearing loss in one ear.
• Pancreatitis: Inflammation of the pancreas, causing stomach pain.

Can Mumps Make Boys Infertile?

This is a huge worry for parents and teenage boys. The answer is: rarely. While mumps can affect the testicles (especially in teenagers and adults), it usually only affects one side. Even if one testicle shrinks (atrophies), the other one can still produce sperm normally. Complete infertility is very rare (less than 1% of mumps cases).

How Did I Catch It?

Mumps spreads through the air when someone with the virus coughs, sneezes, or talks near you. You can also catch it by touching something contaminated with saliva (like a shared cup or toy) and then touching your mouth or nose.

When Can I Go Back to School?

You are most infectious in the few days before and after the swelling starts. You must stay home for 5 days after the swelling started. This helps stop the virus spreading to others.

How Can I Prevent Mumps?

The MMR vaccine (measles, mumps, rubella) is the best protection. Children in the UK get the vaccine at:

• 12-13 months (first dose)
• 3 years 4 months (second dose, or "pre-school booster")

The vaccine is very safe and works well, though it's not 100% effective. About 88% of people who get two doses will be protected from mumps.

Is the MMR Vaccine Safe?

Yes. The MMR vaccine has been used for over 40 years in millions of children worldwide. It is very safe. The most common side effects are a mild fever or rash a week after the injection. The MMR vaccine does NOT cause autism—this myth started from a fraudulent study that has been completely disproven.

What Should I Do If I Think My Child Has Mumps?

1. See your GP to confirm the diagnosis (they will take a swab from your child's mouth).
2. Keep your child at home for 5 days after the swelling started.
3. Give pain relief (paracetamol or ibuprofen).
4. Encourage drinking (water, milk—avoid orange juice as it makes the pain worse).
5. Watch for complications: If your child develops a severe headache, tummy pain, or (in boys) testicular pain, see a doctor urgently.

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14. Examination Focus (MRCPCH/Postgraduate)

Common Exam Scenarios

Scenario 1: Data Interpretation Question

Question: A 5-year-old boy presents with bilateral cheek swelling and fever. Serum amylase is 800 U/L (normal less than 100 U/L). Oral fluid PCR is positive for mumps virus. What is the most likely explanation for the elevated amylase?

Answer: Mumps parotitis. Amylase is universally elevated in mumps due to salivary-type amylase (S-amylase) released from inflamed parotid glands. It does NOT necessarily indicate pancreatitis (which would also elevate pancreatic-type P-amylase and lipase). The elevated amylase alone is non-specific but, combined with positive mumps PCR and clinical picture, confirms mumps.

Scenario 2: Clinical Case (OSCE/PACES)

Stem: You are asked to see a 7-year-old girl in A&E with a 2-day history of right-sided facial swelling and fever. She has not received any vaccinations. On examination, you note swelling anterior to the right ear, with the ear lobe pushed upward. The angle of the mandible is not palpable. What is your differential diagnosis, and how would you confirm the diagnosis?

Model Answer:

• Most likely diagnosis: Mumps parotitis
• Differential diagnoses: Bacterial parotitis, cervical lymphadenitis, salivary calculus, EBV, recurrent parotitis of childhood
• Key differentiating features favouring mumps:
  • Obliteration of mandibular angle (Angle Sign)
  • Ear lobe displacement
  • Unvaccinated (high risk)
  • Fever (though this occurs in bacterial parotitis too)
• Investigations:
  • Oral fluid PCR (gold standard for mumps diagnosis)
  • Serology (IgM) if oral fluid negative or late presentation
  • "FBC, CRP: Normal/mildly elevated in viral infection vs. markedly elevated in bacterial"
  • "Serum amylase: Elevated (supports diagnosis but non-specific)"
• Management:
  • Supportive (analgesia, hydration)
  • Isolate for 5 days
  • Notify Public Health (mumps is notifiable)
  • Check complications (meningism, abdominal pain)

Scenario 3: Viva Question (Oral Exam)

Question: A 16-year-old boy presents 5 days after mumps parotitis with severe left testicular pain and swelling. What are your immediate management steps?

Model Answer:

1. Assess severity: Examine the scrotum (size, colour, tenderness, loss of cremasteric reflex).
2. Exclude testicular torsion (surgical emergency):
   • Testicular torsion: Sudden onset, high-riding testis, absent cremasteric reflex, no relief with elevation (negative Prehn's sign)
   • Mumps orchitis: History of parotitis 4-8 days prior, fever, relief with scrotal elevation (positive Prehn's sign)
   • Doppler ultrasound if diagnostic doubt (torsion shows absent/reduced blood flow; orchitis shows increased flow)
3. Management of orchitis:
   • Analgesia: NSAIDs (ibuprofen) + paracetamol; consider opioids (codeine, morphine) if severe
   • Scrotal support: Tight underwear or athletic support
   • Ice packs: 15 mins on, 15 mins off (wrapped in towel)
   • Bed rest for 2-3 days
4. Reassurance:
   • Symptoms resolve in 1-2 weeks
   • Testicular atrophy occurs in 30-50% of affected testes, but sterility is rare (less than 1%, usually only if bilateral severe)
   • Fertility usually preserved (contralateral testis compensates)
5. Follow-up: Review in 2-3 months to assess for atrophy (clinical examination ± ultrasound).

Scenario 4: MCQ/SBA

Question: A 4-year-old boy is diagnosed with mumps. His mother asks when he can return to nursery. What is the correct advice?

A. Immediately (mumps is not contagious)
B. After 2 days from onset of parotitis
C. After 5 days from onset of parotitis
D. After 10 days from onset of parotitis
E. When the swelling has completely resolved

Answer: C. After 5 days from onset of parotitis. Public Health England/UKHSA guidance states exclusion for 5 days from onset of swelling to minimise transmission during the infectious period.

High-Yield Viva Topics

Red Flag Complications (Must Recognise)

1. Severe headache/neck stiffness/altered consciousness: Aseptic meningitis or encephalitis → Lumbar puncture to exclude bacterial meningitis; admit
2. Scrotal pain/swelling: Orchitis → Exclude testicular torsion (Doppler USS if doubt)
3. Severe epigastric pain/vomiting: Pancreatitis → NBM, IV fluids, admit
4. Sudden hearing loss/tinnitus: Sensorineural deafness → Urgent ENT referral, consider high-dose steroids
5. Seizures/focal neurology: Encephalitis → PICU, neuroimaging

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15. References

Primary Sources

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2. Rubin SA, Plotkin SA. Mumps vaccine. In: Plotkin SA, Orenstein WA, Offit PA, eds. Vaccines. 7th ed. Elsevier; 2018:663-688.
3. Cardemil CV, Dahl RM, James L, et al. Effectiveness of a third dose of MMR vaccine for mumps outbreak control. N Engl J Med. 2017;377(10):947-956. doi:10.1056/NEJMoa1703309. PMID: 28877019.
4. Gouma S, Cremer J, Parkkali S, et al. Mumps virus-specific antibody levels and histocompatibility locus antigen class II alleles as risk factors for mumps despite receiving two doses of measles-mumps-rubella vaccine. J Infect Dis. 2016;213(6):896-904. doi:10.1093/infdis/jiv519. PMID: 26518044.
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10. Public Health England. Guidelines for the public health management of mumps in England. PHE Publications; 2019.
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25. Hyöty H, Hiltunen M, Knip M, et al. A prospective study of the role of coxsackie B and other enterovirus infections in the pathogenesis of IDDM. Diabetes. 1995;44(6):652-657. doi:10.2337/diab.44.6.652. PMID: 7789630.
26. Taylor LE, Swerdfeger AL, Eslick GD. Vaccines are not associated with autism: an evidence-based meta-analysis of case-control and cohort studies. Vaccine. 2014;32(29):3623-3629. doi:10.1016/j.vaccine.2014.04.085. PMID: 24814559.
27. Madsen KM, Hviid A, Vestergaard M, et al. A population-based study of measles, mumps, and rubella vaccination and autism. N Engl J Med. 2002;347(19):1477-1482. doi:10.1056/NEJMoa021134. PMID: 12421889.
28. Public Health England. Immunisation against infectious disease (The Green Book), Chapter 23: Mumps. PHE; 2023.
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31. Wakefield AJ, Murch SH, Anthony A, et al. Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children [retracted]. Lancet. 1998;351(9103):637-641. doi:10.1016/S0140-6736(97)11096-0. PMID: 9500320. [Retracted]
32. Fiebelkorn AP, Lawler J, Curns AT, et al. Mumps postexposure prophylaxis with a third dose of measles-mumps-rubella vaccine, Orange County, New York, USA. Emerg Infect Dis. 2013;19(9):1411-1417. doi:10.3201/eid1909.130299. PMID: 23965756.

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Medical Disclaimer: MedVellum content is for educational purposes and clinical reference only. Clinical decisions should be individualised to patient circumstances and made in consultation with appropriate specialists. All clinical guidelines and evidence are subject to change as new research emerges. Always verify drug doses and contraindications with current national formularies (BNF, BNFc).