Mumps

Mumps is a contagious viral illness marked predominantly by inflammation of the salivary glands, particularly the parotid glands. It has historically been a common childhood disease, although the widespread use of vaccination has dramatically reduced global incidence. The condition affects only humans and is caused by the mumps virus, an RNA virus belonging to the family Paramyxoviridae. While most infections are self-limiting, mumps can lead to a range of complications, some of which may be serious.

Clinical Features and Symptoms

The early clinical features of mumps are typically nonspecific, beginning with fever, headache, malaise, muscle pain and reduced appetite. These initial symptoms precede the hallmark clinical sign of parotid gland inflammation. The swelling, known as parotitis, produces painful enlargement of the parotid glands located at the side of the face. The discomfort is often exacerbated by chewing, swallowing or consuming acidic foods.
Symptoms usually appear 16–18 days after exposure to the virus, although the incubation period can range from 12 to 25 days. Approximately one-third of infected individuals remain asymptomatic, which facilitates silent transmission. In symptomatic patients, parotitis may be unilateral or bilateral and typically resolves within a week.
A subset of patients experience complications, including inflammatory processes affecting various organs. Orchitis, the inflammation of the testes, is most common in post-pubertal males and may lead to reduced fertility and, rarely, sterility. Oophoritis and mastitis may occur in females. Pancreatitis, thyroiditis, nephritis and myocarditis have also been reported. Neurological complications include aseptic meningitis, which occurs in roughly 1–4% of cases, and encephalitis, though the latter is rare. Sensorineural hearing loss, although uncommon, represents one of the more severe potential outcomes.

Virology and Transmission

The mumps virus is a single-stranded, negative-sense RNA virus classified within the genus Rubulavirus. Humans serve as its only natural reservoir. Transmission occurs primarily through respiratory droplets and direct contact with saliva from infected individuals. The virus spreads readily in densely populated environments, including schools, hostels and military barracks.
Infected persons can transmit the virus from approximately seven days before the onset of parotitis to eight days after. Following entry through the upper respiratory tract, the virus replicates within epithelial cells before disseminating to lymph nodes. Subsequent viraemia allows systemic spread to organs such as the salivary glands, central nervous system and reproductive organs.
Laboratory diagnosis may be necessary in regions where mumps is uncommon or where the clinical picture is atypical. Diagnostic tools include serological assays for specific IgM and IgG antibodies, viral culture, and real-time reverse transcription polymerase chain reaction (RT-PCR), the latter being the most sensitive method.
There is no antiviral therapy for mumps. Management is supportive and focuses on rest, hydration and analgesia. Given that the disease is self-limiting, recovery usually occurs within two weeks.

Prevention and Vaccination

Mumps is preventable through vaccination. The combined measles, mumps and rubella (MMR) vaccine is widely used and considered safe and effective. The vaccine contains live attenuated viruses, most commonly the Jeryl Lynn strain for the mumps component. Global vaccination programmes have led to near-elimination of the disease in many countries, reducing both incidence and associated complications.
Most immunisation schedules recommend two doses of the MMR vaccine during childhood, which enhances long-term immunity. Protection extends beyond mumps and includes immunity against measles and rubella. In addition to vaccination, public health measures such as isolation of infected persons reduce transmission, especially in high-density settings.

Historical Background

Mumps has been recognised since antiquity. Chinese medical texts from around 640 BC contained early references to the disease. The Greek physician Hippocrates provided one of the earliest detailed descriptions in approximately 410 BC, documenting an outbreak on the island of Thasos. His writings clearly identified the salivary gland enlargement characteristic of the condition.
Scientific understanding advanced considerably in the eighteenth century when the British physician Robert Hamilton provided a formal clinical account in 1790. During the First World War, mumps represented a significant cause of morbidity among soldiers, particularly due to its high transmissibility in crowded barracks.
A major breakthrough occurred in 1934 when Claude D. Johnson and Ernest W. Goodpasture demonstrated that the agent responsible for mumps was viral. Their experiments involving rhesus macaques established the infectious nature of the disease and confirmed that filtered saliva from infected children could transmit the illness. The virus was successfully isolated in 1945, laying the foundation for vaccine development.
The first mumps vaccine, an inactivated preparation, was introduced in 1948 but proved to confer only short-term immunity. Research in the 1960s led to the development of live attenuated vaccines. Mumpsvax, licensed in 1967 and using the Jeryl Lynn strain isolated by Maurice Hilleman from his daughter, became the standard preparation. By 1977 it was widely recommended, and later combined into the MMR vaccine series. Subsequent formulations such as Priorix, Trimovax and combined MMRV (measles, mumps, rubella and varicella) vaccines expanded immunisation options in later decades.

Epidemiology and Global Trends

Prior to vaccination, mumps outbreaks were widespread worldwide, particularly in temperate climates where seasonal peaks occurred during winter and spring. Infection typically occurred between the ages of 5 and 9 years. After routine immunisation was adopted in many countries, the incidence fell dramatically. Reductions of more than 95% were observed in the United States, Finland and England within a few decades of vaccine introduction.
Japan experienced a notable resurgence in the 1990s after discontinuing the MMR vaccine due to concerns about aseptic meningitis associated with the Urabe strain. This resulted in increased reliance on monovalent mumps vaccines and voluntary immunisation, leading to higher case numbers compared with countries maintaining MMR programmes.
In the early 2000s, outbreaks occurred in several countries with strong vaccination histories, including England, Wales, the Netherlands, Belgium and the United States. Many affected individuals were adolescents and young adults who either missed immunisation or experienced waning immunity. Similar outbreaks continued across university campuses and other crowded settings.

Contemporary Resurgence and Contributing Factors

In the twenty-first century, mumps has re-emerged in periodic outbreaks in regions with high vaccination coverage. Several factors contribute to this phenomenon:

• Waning immunity: Protection from the MMR vaccine gradually decreases over time, particularly in the absence of natural boosting from environmental exposure.
• Incomplete vaccination: Some individuals do not receive the full two-dose schedule, resulting in gaps in herd immunity.
• Vaccine hesitancy: Controversial and ultimately discredited publications in the 1990s, linking MMR vaccination with conditions such as autism and inflammatory bowel disease, reduced public confidence and temporarily lowered uptake in several countries.
• Viral variation: Possible antigenic differences between circulating mumps strains and vaccine strains have been suggested, although evidence remains inconclusive.

These factors have enabled outbreaks in highly mobile and densely populated communities. Adolescents and young adults, particularly those in educational institutions, military settings and sports teams, continue to constitute the majority of reported cases.

Etymology

The term mumps first appeared around 1600 as the plural of mump, meaning to grimace or pout. The name likely refers to the swollen cheeks characteristic of parotitis and the associated difficulty in swallowing. The word mumps was also historically used to denote sullenness or silent displeasure. Alternative names such as epidemic parotitis highlight the condition’s predominant glandular involvement.