What is the pathophysiology of mumps?

Mumps Pathophysiology

Mumps is an acute viral infection characterized by fever and inflammation of the salivary glands (usually parotitis), with a complex pathophysiological process involving respiratory transmission, systemic spread, and potential complications affecting multiple organ systems. 1

Causative Agent and Transmission

• Mumps is caused by the mumps virus (MuV), a member of the Paramyxoviridae family of enveloped, non-segmented, negative-sense RNA viruses 2
• Transmission occurs primarily through respiratory droplets or direct contact with infected saliva 1
• The incubation period averages 16-18 days after exposure, with a range of 12-25 days 1
• Patients are contagious from approximately 7 days before through 8 days after the onset of parotid gland swelling 1

Pathophysiological Progression

• Initial viral entry occurs through the respiratory epithelium 2
• The virus undergoes primary replication in the upper respiratory tract 3
• Viremia (presence of virus in the bloodstream) follows, allowing systemic spread to multiple organs 2
• The virus demonstrates particular tropism for:
  • Salivary glands, especially the parotid glands 1
  • Neural tissues (the virus is highly neurotropic) 2
  • Gonads (testes and ovaries) 1
  • Pancreas 1
  • Meninges 1

Clinical Manifestations and Their Pathophysiological Basis

• Parotitis: The hallmark of mumps infection is inflammation of the parotid glands, which occurs in 60-70% of infections 1

  • Can be unilateral or bilateral 1
  • Results from direct viral invasion of the glandular tissue 2
  • Preceded by prodromal symptoms including fever, headache, malaise, myalgia, and anorexia 1

• Asymptomatic Infection: Approximately 15-20% of infections are completely asymptomatic 1

• Nonspecific or Respiratory Presentation: Up to 50% of infections present with primarily nonspecific or respiratory symptoms rather than classic parotitis 1

• Neurological Complications: The virus is highly neurotropic with laboratory evidence of CNS infection in approximately half of all cases 2

  • Aseptic meningitis occurs in 4-6% of clinical cases 1
  • Meningoencephalitis can lead to permanent sequelae including paralysis, seizures, cranial nerve palsies, aqueductal stenosis, and hydrocephalus 1

• Orchitis: Inflammation of the testes occurs in up to 38% of postpubertal males 1

  • Results from direct viral invasion of testicular tissue 1
  • While painful, sterility is a rare complication 1

• Oophoritis: Inflammation of the ovaries can occur in postpubertal females 1

• Pancreatitis: Results from direct viral invasion of pancreatic tissue 1

• Hearing Loss: In the pre-vaccine era, mumps was a major cause of sensorineural deafness among children 1

  • Hearing loss can be sudden in onset, bilateral, and permanent 1
  • Results from direct viral invasion of the inner ear or cochlear structures 1

• Other Rare Complications: Include myocarditis, endocardial fibroelastosis, arthritis, thrombocytopenia, thyroiditis, mastitis, and glomerulonephritis 1

Age-Related Differences in Pathophysiology

• Inapparent infection is more common among adults than children 1
• Parotitis occurs more commonly among children aged 2-9 years 1
• Most serious complications are more common among adults than children 1
• Severity of disease generally increases with age 1

Pregnancy-Related Pathophysiology

• Women who develop mumps during the first trimester of pregnancy have an increased risk for fetal death 1
• Unlike rubella, mumps infection during pregnancy is not associated with congenital malformations 1

Immune Response

• Infection or vaccination typically confers long-lasting immunity 1
• However, waning immunity can occur over time, particularly with vaccine-induced immunity 4
• Vaccine effectiveness is approximately 88% after two doses, explaining why outbreaks can still occur in highly vaccinated populations 1

Laboratory Diagnosis Reflecting Pathophysiology

• Serological testing for antimumps IgM antibodies and/or seroconversion or 4-fold rise in IgG antibody levels between acute and convalescent phase sera 1
• Direct detection of virus through culture or nucleic acid amplification tests (NAAT) from:
  • Parotid (Stensen) duct/buccal swabs (highest yield) 1
  • Oropharyngeal swabs 1
  • Cerebrospinal fluid in cases of neurological involvement 1
  • Urine (though less sensitive and typically positive later in disease course) 1

Prevention

• The most effective prevention is through vaccination with the live attenuated mumps vaccine, typically administered as part of the MMR (measles, mumps, rubella) vaccine 1
• Two doses are recommended for optimal protection 1
• Vaccination has reduced mumps incidence by 99% in the United States since its introduction 1