Mumps
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, 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.
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 settings. 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".History
According to Chinese medical literature, mumps was recorded as far back as 640 B.C. The Greek physician Hippocrates documented an outbreak on the island of Thasos in approximately 410 B.C. and provided a fuller description of the disease in the first book of Epidemics in the Corpus Hippocraticum. 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.In 1945, the mumps virus was isolated for the first time. Just a few years later, in 1948, an inactivated vaccine using killed viruses was invented. This vaccine provided only short-term immunity and was later discontinued. It was replaced in the 1970s with vaccines that have live but weakened viruses, which are more effective at providing long-term immunity than the inactivated vaccine. The first of these vaccines was Mumpsvax, licensed on 30 March 1967, which used the Jeryl Lynn strain. Maurice Hilleman created this vaccine using the strain taken from his five-year-old daughter, Jeryl Lynn. Mumpsvax was recommended for use in 1977, and the Jeryl Lynn strain continues to be used.
Hilleman worked to combine the attenuated mumps vaccines with the measles and rubella vaccines, creating the MMR-1 vaccine. In 1971, a newer version, MMR-2, was approved for use by the US Food and Drug Administration. In the 1980s, the benefit of multiple doses was recognized, so a two-dose immunization schedule was widely adopted. With MMR-2, four other MMR vaccines have been created since the 1960s: Triviraten, Morupar, Priorix, and Trimovax. Since the mid-2000s, two MMRV vaccines have been in use: Priorix-Tetra and ProQuad.
The United States began to vaccinate against mumps in the 1960s, with other countries following suit. From 1977 to 1985, 290 cases per 100,000 people were diagnosed each year worldwide. Although few countries recorded mumps cases after they began vaccination, those that did reported dramatic declines. From 1968 to 1982, cases declined by 97% in the U.S., and in Finland cases were reduced to less than one per 100,000 people per year, and a decline from 160 cases per 100,000 to 17 per 100,000 per year in England was observed from 1989 to 1995. By 2001, there had been a 99.9% reduction in the number of cases in the U.S. and similar near-elimination in other vaccinating countries.
In Japan in 1993, concerns over the rates of aseptic meningitis following MMR vaccination with the Urabe strain prompted the removal of MMR vaccines from the national immunization program, resulting in a dramatic increase in the number of cases. Japan provides voluntary mumps vaccination separately from measles and rubella. Starting in the mid-1990s, controversies surrounding the MMR vaccine emerged. One paper connected the MMR vaccine to Crohn's disease in 1995, and another in 1998 connected it to autism spectrum disorders and inflammatory bowel disease. These papers are now considered to be fraudulent and incorrect, and no association between the MMR vaccine and the aforementioned conditions has been identified. Despite this, their publication led to a significant decline in vaccination rates, ultimately causing measles, mumps, and rubella to reemerge in places with lowered vaccination rates.
Outbreaks in the 21st century include more than 300,000 cases in China in 2013 and more than 56,000 cases in England and Wales in 2004–2005. In the latter outbreak, most cases were reported in 15–24 year olds who were attending colleges and universities. This age group was thought to be vulnerable to infection because of the MMR vaccine controversies when they should have been vaccinated or MMR vaccine shortages that had also occurred at that time. Similar outbreaks in densely crowded environments have frequently occurred in many other countries, including the U.S., the Netherlands, Sweden, and Belgium.
Resurgence
In the 21st century, mumps has reemerged in many places that vaccinate against it, causing recurrent outbreaks. These outbreaks have largely affected adolescents and young adults in densely crowded spaces, such as schools, sports teams, religious gatherings, and the military, and it is expected that outbreaks will continue to occur. The cause of this reemergence is subject to debate, and various factors have been proposed, including waning immunity from vaccination, low vaccination rates, vaccine failure, and potential antigenic variation of the mumps virus.Waning immunity from vaccines is likely the primary cause of the mumps resurgence. In the past, subclinical natural infections provided boosts to immunity similar to vaccines. As time went on with vaccine use, these asymptomatic infections declined in frequency, likely leading to a reduction in long-term immunity against mumps. With less long-term immunity, the effects of waning vaccine immunity became more prominent, and vaccinated individuals have frequently fallen ill from mumps. A third dose of the vaccine provided in adolescence has been considered to address this as some studies support this. Other research indicates that a third dose may be useful only for short-term immunity in responding to outbreaks, which is recommended for at-risk persons by the Advisory Committee on Immunization Practices of the Centers for Disease Control and Prevention.
Low vaccination rates have been implicated as the cause of some outbreaks in the UK, Canada, Sweden, and Japan, whereas outbreaks in other places, such as the U.S., the Czech Republic, and the Netherlands, have occurred mainly among the vaccinated. Compared to the measles and rubella vaccines, mumps vaccines appear to have a relatively high failure rate, varying depending on the vaccine strain. This has been addressed by providing two vaccine doses, supported by recent outbreaks among the vaccinated having primarily occurred among those who received only one dose. Lastly, certain mumps virus lineages are highly divergent genetically from vaccine strains, which may cause a mismatch between protection against vaccine strains and non-vaccine strains, though research is inconclusive on this matter.