What are the diagnostic steps and management for a patient suspected of having mumps?

Mumps Diagnosis

Laboratory confirmation is essential for all suspected mumps cases because clinical diagnosis alone misdiagnoses approximately one-third of patients, and you should immediately obtain mumps IgM antibody testing and viral PCR from parotid duct swabs within 9 days of symptom onset. 1, 2

Clinical Case Definition

A clinical case requires acute onset of unilateral or bilateral tender, self-limited parotid or salivary gland swelling lasting ≥2 days without other apparent cause. 1 However, do not rely on clinical diagnosis alone—parotitis has multiple infectious and noninfectious causes, and bilateral presentation is not universal. 2, 3

Key Distinguishing Features from Bacterial Sialadenitis

• Bacterial sialadenitis: unilateral swelling, purulent discharge from Stensen's duct, fever, predisposing factors (dehydration, ductal obstruction) 2
• Mumps: typically bilateral swelling ≥2 days, no purulent discharge, though unilateral presentations occur 2, 3

Laboratory Confirmation (Three Accepted Criteria)

Primary diagnostic approach:

1. Mumps-specific IgM antibody detection (most practical confirmatory test for acute infection) 1, 2

2. Viral PCR from parotid duct swabs obtained after massaging the parotid gland for 30 seconds, collected within 9 days of symptom onset 1, 2

3. Significant rise in mumps IgG antibody titers between acute and convalescent-phase sera by standard serologic assay 1, 2

Additional Specimen Collection

• Buccal (saliva) swabs for viral culture or PCR within 9 days of symptoms 1, 2
• Urine PCR remains positive for at least 5 days after oral detection (less sensitive but useful if oral swabs missed) 1, 2
• Throat and rectal swabs for enterovirus if vesicles present or enterovirus suspected 1

Critical Diagnostic Pitfalls

Always test for HIV in all patients with parotitis regardless of apparent risk factors—HIV can present with parotid swelling during acute seroconversion or as chronic parotitis. 1, 2, 4

Differential Diagnoses Requiring Laboratory Exclusion

• Other viral causes: EBV, CMV, HIV, influenza A, parainfluenza, adenovirus, enteroviruses 5
• Bacterial sialadenitis: requires different management with antibiotics 2
• Non-infectious causes: salivary duct stones, autoimmune conditions 1

Immediate Actions Upon Suspected Diagnosis

1. Implement droplet precautions immediately and isolate patient for 5 days after parotitis onset 4
2. Obtain laboratory confirmation before assuming viral etiology 4
3. Assess vaccination history—lack of MMR vaccination or birth after 1957 without documented immunity increases risk 2
4. Monitor for complications: orchitis in postpubertal males (up to 38% of cases), aseptic meningitis/encephalitis, pancreatitis (days 3-5), hearing loss 4, 6

Case Classification System

• Confirmed case: meets laboratory criteria OR meets clinical definition AND epidemiologically linked to confirmed/probable case 1
• Probable case: meets clinical definition, not epidemiologically linked, noncontributory or no laboratory testing 1
• Two epidemiologically linked probable cases = confirmed even without laboratory confirmation 1

Common Diagnostic Errors to Avoid

• Do not prescribe antibiotics for confirmed viral parotitis—this contributes to antimicrobial resistance without clinical benefit 4
• Do not rely on bilateral presentation—unilateral mumps occurs and can involve synchronous parotid and submandibular glands 3
• Do not skip HIV testing—this is mandatory regardless of perceived risk factors 1, 2, 4
• Do not delay laboratory confirmation—clinical diagnosis has 33% false positive rate 1, 2