Mumps is a highly contagious, vaccine-preventable viral disease caused by the mumps virus. Initial symptoms of mumps are non-specific and include fever, headache, malaise, muscle pain, and loss of appetite. These symptoms are usually followed by painful swelling around the side of the face (the parotid glands, called parotitis), which is the most common symptom of a mumps infection. Symptoms typically occur 16 to 18 days after exposure to the virus. About one-third of people with a mumps infection do not have any symptoms (asymptomatic).

Complications are rare but include deafness and a wide range of inflammatory conditions, of which inflammation of the testes, breasts, ovaries, pancreas, meninges, and brain are the most common. Viral meningitis can occur in 1/4 of people with mumps. Testicular inflammation may result in reduced fertility and, rarely, sterility.

Humans are the only natural hosts of the mumps virus. The mumps virus is an RNA virus in the family Paramyxoviridae. The virus is primarily transmitted by respiratory secretions such as droplets and saliva, as well as via direct contact with an infected person. Mumps is highly contagious and spreads easily in densely populated environments. Transmission can occur from one week before the onset of symptoms to eight days after. During infection, the virus first infects the upper respiratory tract. From there, it spreads to the salivary glands and lymph nodes. Infection of the lymph nodes leads to the presence of the virus in the blood, which spreads the virus throughout the body. In places where mumps is common, it can be diagnosed based on clinical presentation. In places where mumps is less common, however, laboratory diagnosis using antibody testing, viral cultures, or real-time reverse transcription polymerase chain reaction may be needed.

There is no specific treatment for mumps, so treatment is supportive and includes rest and pain relief. Mumps infection is usually self-limiting, coming to an end as the immune system clears the infection. Infection can be prevented with vaccination. The MMR vaccine is a safe and effective vaccine to prevent mumps infections and is used widely around the world. The MMR vaccine also protects against measles and rubella. The spread of the disease can also be prevented by isolating infected individuals.

Mumps historically has been a highly prevalent disease, commonly occurring in outbreaks in densely crowded spaces. In the absence of vaccination, infection normally occurs in childhood, most frequently at the ages of 5–9. Symptoms and complications are more common in males and more severe in adolescents and adults. Infection is most common in winter and spring in temperate climates, whereas no seasonality is observed in tropical regions. Written accounts of mumps have existed since ancient times, and the cause of mumps, the mumps virus, was discovered in 1934. By the 1970s, vaccines had been created to protect against infection, and countries that have adopted mumps vaccination have seen a near-elimination of the disease. In the 21st century, however, there has been a resurgence in the number of cases in many countries that vaccinate, primarily among adolescents and young adults, due to multiple factors such as waning vaccine immunity and opposition to vaccination.

Etymology

The word "mumps" was first attested circa 1600 and is the plural form of "mump", meaning "grimace", originally a verb meaning "to whine or mutter like a beggar". The disease was likely called mumps due to the swelling caused by mumps parotitis, reflecting its impact on facial expressions and the painful, difficult swallowing that it causes. "Mumps" was also used starting from the 17th century to mean "a fit of melancholy, sullenness, silent displeasure". Mumps is sometimes called "epidemic parotitis". In modern times, the disease was first described scientifically in 1790 by British physician Robert Hamilton in Transactions of the Royal Society of Edinburgh. During the First World War, mumps was one of the most debilitating diseases among soldiers. In 1934, the etiology of the disease, the mumps virus, was discovered by Claude D. Johnson and Ernest William Goodpasture. They found that rhesus macaques exposed to saliva taken from humans in the early stages of the disease developed mumps. Furthermore, they showed that mumps could then be transferred to children via filtered and sterilized, bacteria-less preparations of macerated monkey parotid tissue, showing that it was a viral disease. averaging 16–18 days. 20–40% of infections are asymptomatic or are restricted to mild respiratory symptoms, sometimes with a fever. Over the course of the disease, three distinct phases are recognized: prodromal, early acute, and established acute. The prodromal phase typically has non-specific, mild symptoms such as a low-grade fever, headache, malaise, muscle pain, loss of appetite, and sore throat. In the early acute phase, as the mumps virus spreads throughout the body, systemic symptoms emerge. Most commonly, parotitis occurs during this time period. During the established acute phase, orchitis, meningitis, and encephalitis may occur, and these conditions are responsible for the bulk of mumps morbidity. of symptomatic cases and 60–70% of total infections. During mumps parotitis, usually both the left and right parotid glands experience painful swelling, Other salivary glands, namely the submandibular, and sublingual glands, may also swell. Inflammation of these glands is rarely the only symptom. after the onset of parotitis but can occur up to six weeks later. During mumps orchitis, the scrotum is tender and inflamed. It occurs in 10–40% of pubertal and post-pubertal males who contract mumps. Usually, mumps orchitis affects only one testis but in 10–30%

  • Oophoritis, inflammation of an ovary, in 5–10% of post-pubertal women, which usually presents as pelvic pain
  • Aseptic meningitis, inflammation of the meninges, in 5–10% of cases and 4–6% of those with parotitis, typically occurring 4–10 days after the onset of symptoms. Mumps meningitis can also occur up to one week before parotitis as well as in the absence of parotitis. It is commonly accompanied by fever, headache, vomiting, and neck stiffness.
  • Pancreatitis, inflammation of the pancreas, in about 4% of cases, which causes severe pain and tenderness in the upper abdomen below the ribs
  • Encephalitis, inflammation of the brain, in less than 0.5% of cases.
  • Nephritis, inflammation of the kidneys, which is rare because kidney involvement in mumps is usually benign but leads to presence of the virus in urine
  • Inflammation of the joints (arthritis), which may affect at least five joints (polyarthritis), multiple nerves in the peripheral nervous system (polyneuritis), pneumonia, Among children, seizures occur in about 20–30% of cases involving the central nervous system. Humans are the only natural host of the mumps virus. MuV's genome is made of RNA and contains seven genes that encode nine proteins. In MuV particles, the genome is encased by a helical capsid. The capsid is surrounded by a viral envelope that has spikes protruding from its surface. MuV particles are pleomorphic in shape and range from 100 to 600 nanometers in diameter.

The replication cycle of MuV begins when the spikes on its surface bond to a cell, which then causes the envelope to fuse with the host cell's cell membrane, releasing the capsid into the host cell's cytoplasm. Upon entry, the viral RNA-dependent RNA polymerase (RdRp) transcribes messenger RNA (mRNA) from the genome, which is then translated by the host cell's ribosomes to synthesize viral proteins. RdRp then begins replicating the viral genome to produce progeny.

Pathogenesis

Many aspects of the pathogenesis of mumps are poorly understood and are inferred from clinical observations and experimental infections in laboratory animals. These animal studies may be unreliable due to unnatural methods of inoculation. Neutralizing antibodies in the salivary glands may be important in restricting MuV replication and transmission via saliva, as the level of viral secretion in saliva inversely correlates to the quantity of MuV-specific IgA produced.

Mumps orchitis is usually diagnosed by white blood cell count, with normal differential white blood cell counts. A complete blood count can show above or below-average white blood cell count and an elevated C-reactive protein level. Urine analysis can exclude bacterial infections. If orchitis is present with normal urine analysis, negative urethral cultures, and negative midstream urine, then that can indicate mumps orchitis. Ultrasounds typically show diffuse hyper-vascularity, increased volume of the testes and epididymis, lower than usual ability to return ultrasound signals, swelling of the epididymis, and formation of hydroceles. Echo color Doppler ultrasound is more effective at detecting orchitis than ultrasound alone. and as a part of the MMRV vaccine, which also protects against measles, rubella, chickenpox, and shingles. More than 120 countries have adopted mumps vaccination, but coverage remains low in most African, South Asian, and Southeast Asian countries. Vaccination is expected to be capable of neutralizing wild-type MuVs, which are not included in the vaccine, since they do not appear to evade vaccine-derived immunity. Mild adverse reactions are relatively common, including fever and rash, and is estimated to be between 79% and 95%, lower than the degree of protection against measles and rubella. This, however, has still been sufficient to nearly eliminate mumps in countries that vaccinate against it as well as significantly reduce frequencies of complications among the vaccinated. A difficulty in assessing vaccine effectiveness is that there is no clear correlate of immunity, so it is not possible to predict if a person has acquired immunity from the vaccine.

Prognosis

The prognosis for most people who experience mumps is excellent as long-term complications and death are rare. Hospitalization is typically not required.