What is Mumps?
Mumps is an acute viral infection caused by a single-stranded RNA paramyxovirus that characteristically produces fever and inflammation of the salivary glands, most commonly presenting as parotitis (swelling of the parotid glands). 1, 2
Clinical Presentation
The disease manifests with considerable variability:
- Classic presentation: Bilateral or unilateral parotid gland swelling with onset typically 16-18 days after exposure (incubation range: 15-24 days) 2, 3
- Prodromal symptoms: Fever, headache, malaise, myalgia, and anorexia precede parotitis by several days 2
- Subclinical disease: 20-40% of infections are asymptomatic, and only 30-40% produce typical acute parotitis 1, 2
- Nonspecific illness: Up to 50% present with primarily respiratory symptoms without classic parotitis 2
Important caveat: Clinical diagnosis is unreliable—many rash illnesses mimic mumps, and many mumps infections go unrecognized. Parotitis can have multiple infectious and noninfectious causes. 1
Complications
Severity increases with age, with most serious complications more common in adults than children 2:
- Orchitis: Occurs in up to 38% of postpubertal males, though sterility is rare 2
- Aseptic meningitis: Affects 4-6% of clinical cases, typically mild 2
- Meningoencephalitis: Can cause permanent sequelae including paralysis, seizures, cranial nerve palsies, aqueductal stenosis, and hydrocephalus 2
- Sensorineural deafness: In the prevaccine era, mumps was a major cause of childhood deafness; can be sudden, bilateral, and permanent 2
- Pregnancy complications: Increased risk for fetal death in first trimester, though not associated with congenital malformations 2
Critical point: Serious complications can occur without evidence of parotitis. 2
Transmission
- Route: Respiratory droplets and saliva 4
- Contagious period: Virus can be isolated from saliva 7 days before through 8 days after onset of parotid swelling 5
- Infectivity: Less contagious than measles but moderately infectious 1, 3
- Transmission timing: Can occur from persons with subclinical or clinical infections during prodromal or symptomatic phases 4
Epidemiology
The landscape has shifted dramatically:
- Prevaccine era: Approximately 186,000 cases annually in the United States 1
- Post-vaccine introduction (1967): 99% decline in cases 1, 2
- Recent resurgence: Despite vaccination programs, outbreaks have occurred, notably 6,584 cases in 2006 (largest outbreak in 20 years), primarily affecting college-aged students (18-24 years), many of whom had received 2 doses of vaccine 1
This resurgence pattern highlights that even highly vaccinated populations remain vulnerable, likely due to waning immunity or vaccine effectiveness issues against circulating genotypes.