• Mumps Virus

• Genus: Rubulavirus

• Family: Paramyxoviridae (same family as measles virus, respiratory syncytial virus – RSV)

• It is an RNA virus. There is generally considered to be only one serotype of mumps virus.

Reservoir

• Humans are the only known natural host and reservoir for the mumps virus.

Mode of Transmission
Mumps is highly contagious and spreads primarily through:

• Direct contact with saliva or respiratory droplets from an infected person (e.g., when an infected person coughs, sneezes, or talks).

• Contact with contaminated fomites (objects or surfaces) that have been touched by an infected person (e.g., sharing cups, utensils, touching doorknobs and then touching the mouth or nose), though this is a less common route.

Period of Communicability (When an Infected Person Can Spread the Virus)

• An infected person is typically contagious from about 1-2 days before the onset of parotid swelling (or other symptoms) until about 5 days after the onset of swelling.

• Some individuals with mumps infection may be asymptomatic (show no symptoms) but can still transmit the virus.

Incubation Period

• Typically 16 to 18 days after exposure, but can range from 12 to 25 days.

Pathogenesis (How it Causes Disease)

• The mumps virus enters the body through the respiratory tract (nose, mouth, throat).

• It replicates in the epithelial cells of the upper respiratory tract and regional lymph nodes.

• The virus then spreads through the bloodstream (viremia) to various target tissues, including:

  • Salivary glands (especially parotid glands)

  • Central nervous system (meninges, brain)

  • Testes, ovaries

  • Pancreas

  • Other organs (less commonly, e.g., thyroid, kidneys, heart, joints).

• Inflammation in these target tissues leads to the characteristic symptoms of mumps.

Clinical Manifestations (Signs and Symptoms)
About 20-40% of mumps infections are asymptomatic or present with non-specific respiratory symptoms. For those with symptomatic illness:

• Prodromal Phase (1-2 days before parotid swelling):

  • Low-grade fever

  • Malaise, fatigue

  • Headache

  • Myalgia (muscle pain)

  • Anorexia (loss of appetite)

• Acute Phase (Parotitis – Salivary Gland Involvement):

  • Parotid gland swelling (parotitis): This is the hallmark symptom.

    • Usually starts with pain and tenderness in one parotid gland, followed by swelling.

    • The other parotid gland often swells a few days later (bilateral involvement occurs in about 70-90% of symptomatic cases).

    • Swelling can obscure the angle of the jaw and push the earlobe upwards and outwards.

    • Pain is often aggravated by chewing, swallowing, or consuming acidic foods/drinks (e.g., citrus juice).

    • Swelling typically peaks in 1-3 days and gradually subsides over 3-7 days (can last up to 10 days).

  • Other salivary glands: Submandibular and sublingual glands can also be affected, causing swelling under the jaw or tongue.

  • Fever may accompany the swelling.

• Other Systemic Symptoms and Complications (Can occur with or without parotitis):

  • Orchitis (Inflammation of the testes):

    • Most common complication in post-pubertal males (occurs in up to 30-40% of those infected after puberty).

    • Usually unilateral (one testis), but can be bilateral.

    • Characterized by abrupt onset of testicular pain, tenderness, swelling, nausea, vomiting, and fever.

    • Typically occurs 4-8 days after parotitis onset but can occur before or without parotitis.

    • May lead to testicular atrophy (shrinkage) in about 30-50% of affected testes. Impaired fertility is rare, and sterility (inability to father a child) is very rare even with bilateral orchitis.

  • Oophoritis (Inflammation of the ovaries):

    • Occurs in about 5% of post-pubertal females.

    • Symptoms include lower abdominal pain, tenderness, fever, and vomiting.

    • Rarely associated with impaired fertility. Mastitis (inflammation of the breast) can also occur.

  • Meningitis (Aseptic Meningitis):

    • Most common neurological complication. Clinical signs of meningitis occur in up to 10-15% of cases, but CSF pleocytosis (increased white blood cells in cerebrospinal fluid, indicating inflammation) can be found in up to 50% if a lumbar puncture is done.

    • Symptoms include headache, stiff neck, fever, vomiting, lethargy.

    • Usually mild and self-limiting with full recovery.

  • Encephalitis (Inflammation of the brain):

    • Much rarer than meningitis (e.g., <1 per 100,000 cases in vaccinated populations, but higher in unvaccinated).

    • Can be serious, with symptoms like seizures, altered consciousness, focal neurological deficits. May lead to permanent neurological damage or death.

  • Hearing Loss (Sensorineural):

    • Can occur, usually unilateral (one ear), and is often permanent.

    • May be sudden in onset. A significant cause of acquired deafness in individuals before widespread vaccination.

  • Pancreatitis (Inflammation of the pancreas):

    • Uncommon, characterized by epigastric pain, tenderness, nausea, vomiting, and fever.

    • Usually mild and self-limiting.

  • Other rare complications: Thyroiditis, myocarditis, nephritis, arthritis.

  • Mumps in Pregnancy: First-trimester infection may be associated with an increased risk of spontaneous abortion, but mumps has not been definitively linked to congenital malformations.

Diagnosis
Diagnosis is often made clinically based on characteristic parotitis, especially during an outbreak.

• Clinical Diagnosis: Presence of acute unilateral or bilateral tender swelling of the parotid or other salivary glands lasting at least 2 days, without other apparent cause.

• Laboratory Confirmation (Recommended, especially for sporadic cases or to confirm outbreaks):

  • Viral Isolation: Mumps virus can be cultured from saliva, urine, or cerebrospinal fluid (CSF), typically within the first week of illness. Buccal (cheek) swabs are preferred.

  • Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR): Detects mumps virus RNA. More rapid and sensitive than culture. Can be performed on saliva (buccal swab), urine, or CSF. This is the preferred diagnostic method.

  • Serological Tests:

    • Detection of IgM antibodies: Presence of mumps-specific IgM antibodies indicates recent infection. Usually detectable within a few days of symptom onset and persists for several weeks.

    • Detection of IgG antibodies: A significant rise (e.g., fourfold or greater) in mumps-specific IgG antibody titers between acute-phase serum (taken early in illness) and convalescent-phase serum (taken 2-4 weeks later) confirms infection. A single positive IgG indicates past infection or vaccination.

    • IgM can be falsely negative early in illness or in previously vaccinated individuals (who may have a modified immune response). PCR is often more reliable in vaccinated individuals.

Treatment

• There is no specific antiviral treatment for mumps.

• Treatment is supportive and symptomatic, aimed at relieving symptoms and managing discomfort.

• General Measures:

  • Rest.

  • Analgesics and antipyretics (e.g., paracetamol, ibuprofen) for pain and fever.

  • Adequate fluid intake.

  • Application of warm or cold compresses to swollen parotid glands for comfort.

  • Avoidance of acidic foods and drinks that can stimulate saliva production and worsen parotid pain.

  • Soft diet if chewing is painful.

• Management of Complications:

  • Orchitis: Bed rest, scrotal support (e.g., athletic supporter), ice packs, and analgesics.

  • Meningitis/Encephalitis: Supportive care, hospitalization may be required for severe cases.

  • Other complications are managed symptomatically.

Prevention

• 1. Vaccination (Most Effective Method):

  • The Mumps vaccine is usually given as part of the MMR (Measles, Mumps, Rubella) vaccine or MMRV (Measles, Mumps, Rubella, Varicella) vaccine.

  • It is a live, attenuated (weakened) virus vaccine.

  • Recommended Schedule (varies slightly by country):

    • First dose: Typically given at 12-15 months of age.

    • Second dose: Typically given at 4-6 years of age (before school entry).

  • Two doses of MMR vaccine are about 88% effective (range: 66%-95%) at preventing mumps; one dose is about 78% effective (range: 49%-92%).

  • Vaccination is crucial for preventing outbreaks and reducing the incidence of complications.

  • Outbreaks can still occur in highly vaccinated populations due to waning immunity over time, vaccine failure in a small percentage of individuals, or intense exposure. A third dose of MMR may be recommended during outbreaks in certain settings.

• 2. Infection Control Measures (During Outbreaks or for Infected Individuals):

  • Isolation: Infected individuals should be isolated to prevent spread. They should stay home from school, childcare, or work for 5 days after the onset of parotid swelling.

  • Respiratory Hygiene and Cough Etiquette: Covering mouth and nose when coughing or sneezing, using tissues and disposing of them properly.

  • Hand Hygiene: Frequent handwashing with soap and water or using alcohol-based hand sanitizer.

  • Avoid Sharing: Do not share cups, utensils, or other personal items.

  • Cleaning and Disinfection: Regularly clean frequently touched surfaces.

Prognosis

• Mumps is generally a self-limiting illness, and most people recover fully without long-term consequences.

• Complications like meningitis usually resolve completely.

• Permanent hearing loss, though rare, can occur.

• Sterility from orchitis is very rare.

• Encephalitis is rare but can be serious.

Widespread vaccination has dramatically reduced the incidence of mumps and its complications in many countries, but outbreaks continue to occur, highlighting the importance of maintaining high vaccination coverage.