Overview
Mumps is a viral illness common in people who have not been vaccinated with the MMR vaccine. It used to be a very common childhood illness but the introduction of the MMR vaccination effectively wiped it out although there are still intermittent outbreaks. The condition generally does not require treatment but can sometimes lead to more serious complications. It can be associated with other infections and other infections can mimic the symptoms. In this article, we describe more of the condition and discuss potential complications, and other infections.
What is mumps?
Mumps is a viral infection, most common in children and young adults. It is generally characterised by swelling of the salivary glands, especially the parotid glands, which leads to the common sign of facial swelling. Meningitis, pancreatitis, encephalitis, hearing loss, orchitis, and oophoritis are potential complications of the infection.
The mumps virus
The name of the virus that causes mumps is paramyxovirus. This virus is part of the Paramyxoviridae family which includes three types:
- Parainfluenza viruses and mumps virus
- Pneumovirus, which includes respiratory syncytial virus
- Morbillivirus which includes the measles virus1
How is mumps spread?
The mumps virus is spread in respiratory droplets. These droplets can be passed into the surrounding area by talking, laughing, coughing, or sneezing. Mumps can then be caught from an infectious person by being in close contact with them or the surfaces that they have passed droplets onto.
Infectious period
People with mumps are generally infectious from two days before symptoms show and around five days after.2 The mumps virus is excreted in the saliva from approximately one week before up to one week after the onset of salivary gland swelling.
How does mumps affect the body?
Primary infection with the mumps virus affects the glandular and nervous tissue, resulting in inflammation, cellular responses, and cell death. These cellular responses ultimately make the body immune to the virus.2 The World Health Organisation, WHO, have stated that natural infection with the mumps virus is thought to give the individual lifelong immunity.
Around 30-50% of mumps infections are thought to cause no symptoms (asymptomatic) or cause only mild respiratory symptoms with fever.3
The main effect of mumps infection is on the salivary glands which causes facial swelling and inflammation, particularly of the parotid glands. This observable feature on the individual can make up part of a clinical diagnosis.
Incidence of mumps
The mumps virus is a respiratory virus or pathogen which is spread largely by 2–5-year old children.3 According to the World Health Organisation (WHO), The global incidence of mumps in the absence of immunization is in the range of 100 –1000 cases/100 000 population annually with epidemic peaks every 2–5 years. In rural areas, it is intermittent, reappearing there every 5 to 7 years and can hit epidemic proportions. In temperate climates, the incidence peaks from January to May.
Common symptoms of mumps
The most well-known symptom of mumps is the painful swelling at the side of the face due to swelling of the parotid glands. This is known as parotitis. People often refer to a “hamster” or “chipmunk” look. An infected person can also experience fever, headache, loss of appetite, and general malaise. Parotitis can be painful and is usually seen on both sides of the face (bilateral). It usually develops 2–3 weeks after exposure and lasts for around two to three days.
Other infectious causes of parotitis
Parotitis can also be caused by:
- Epstein-Barr virus, influenza A virus, parainfluenza virus types 1 and 3 and enteroviruses
- Staphylococcus aureus, Streptococcus species,and atypical mycobacteria
- Mastoiditis and dental abscess
Complications of mumps
The other more serious symptoms of mumps are:
- Orchitis
- Meningitis
- Encephalitis
- Pancreatitis
- Deafness
Orchitis
Orchitis refers to swelling and inflammation of the testicles. It usually occurs in one testicle but can spread to the two. It is the most common symptom of mumps that affects glands other than the salivary gland manifestation. It is thought to occur as a symptom in 10–20% of post-pubertal men infected with mumps. Viral orchitis can usually resolve on its own without treatment. It can decrease sperm count and potentially cause infertility.
Oophoritis
Oophoritis is a rare complication in females of mumps that occurs when the ovaries swell.
Meningitis
Meningitis is inflammation of the outer membrane that covers the brain and spinal cord or inflammation of the brain.This can occur as a complication of mumps infection if the virus spreads to the brain. Symptoms can be headache, neck stiffness, and sensitivity to light (photophobia). It usually resolves by itself, but in rare cases can be severe and life threatening.
Viral meningitis can also be caused by:
Encephalitis
Encephalitis refers to inflammation of the brain. Mumps encephalitis is a rare but very serious complication of mumps which can lead to neurological damage, other complications and can be potentially fatal. It needs to be treated urgently and often an antiviral medication such as aciclovir will be required.
Pancreatitis
Pancreatitis refers to inflammation of the pancreas which can be a serious and life-threatening condition. The NHS website estimates that about 1 in 25 cases of mumps lead to short-term inflammation of the pancreas (acute pancreatitis).
Hearing loss
In some instances, mumps can lead to deafness or hearing loss. Around 1 in 1000 cases of mumps in children are thought to lead to hearing loss.4
Mumps deafness is usually sudden, profound, or complete and is usually irreversible. It is not fully known how the mumps virus causes this complication.5
Other viral infections that mimic mumps
Children who have been vaccinated by MMR can still develop other diseases caused by viruses such as:
- Epstein-Barr virus (EBV)
- Parainfluenza virus
- Adenoviruses
- Herpes virus
- Parvovirus B19
- Cytomegalovirus
Infection with these viruses can mimic the symptoms of mumps which can make diagnosis of mumps complicated.6
MMR vaccine
The mumps vaccine is included in the vaccination we know as MMR which vaccinates against measles, mumps, and rubella. It is a live vaccine introduced in the 1960s and has proved to be one of the most cost-effective interventions in global health ever.7 These vaccines contain live attenuated amounts of the virus and are given to babies at one year of age, then a second dose at around 3-5 years of age.
Herd immunity
Herd immunity occurs when a significant portion of a population becomes immune to an infectious disease which limits further disease spread. Diseases spread when some of a population is susceptible to the disease. Herd immunity occurs when a significant portion of a population becomes immune to an infectious disease and the risk of spread from person to person decreases; those who are not immune are indirectly protected because ongoing disease spread is very small. People who cannot be vaccinated due to compromised immunity or babies under the age of 12 months depend on this herd immunity for protection.
Challenges to vaccination uptake
Global MMR vaccination rates are still not optimal and recent drops in uptake have resulted in some outbreaks of mumps and measles. Herd immunity drops when vaccination uptake drops. In the late 1990s, a paper claiming links with MMR and autism unfortunately led to some parents refusing to vaccinate their children.8 Even after the author of that paper was discredited and the journal withdrawn, it harmed the perception of the vaccine safety and uptake rates. A further problem is that several famous people or politicians declare themselves not in favour of vaccines, allowing the spread of the anti-vaccine movement.9 The presence of anti-vaccination websites and social media threads also contribute to the increase of anti-vaccine support.
Summary
Mumps is an infectious viral illness that occurs most often in unvaccinated children and young adults. The most common symptom is a swollen face due to inflamed parotid glands. Whilst it is normally a relatively minor illness that resolves without treatment, there are potentially serious complications and associated infections that can be life threatening. The key to preventing mumps is the continued use of the MMR vaccine and challenging public perception that diminishes uptake.
References
- Enders G. Paramyxoviruses. In: Baron S, editor. Medical Microbiology. 4th ed., Galveston (TX): University of Texas Medical Branch at Galveston; 1996. Available from: https://www.ncbi.nlm.nih.gov/books/NBK8461/
- Lam E, Rosen JB, Zucker JR. Mumps: an Update on Outbreaks, Vaccine Efficacy, and Genomic Diversity. Clin Microbiol Rev 2020;33:e00151-19. Available from: https://doi.org/10.1128/CMR.00151-19.
- Cooney MK, Fox JP, Hall CE. THE SEATTLE VIRUS WATCH1. American Journal of Epidemiology 1975;101:532–51. Available from: https://doi.org/10.1093/oxfordjournals.aje.a112125.
- Hashimoto H, Fujioka M, Kinumaki H. An Office-Based Prospective Study of Deafness in Mumps. Pediatric Infectious Disease Journal 2009;28:173–5. Available from: https://doi.org/10.1097/INF.0b013e31818a8ca8.
- Bitnun S, Rakover Y, Rosen G. Acute bilateral total deafness complicating mumps. J Laryngol Otol 1986;100:943–5. Available from: https://doi.org/10.1017/S0022215100100362.
- Magurano F, Baggieri M, Marchi A, Bucci P, Rezza G, Nicoletti L. Mumps clinical diagnostic uncertainty. European Journal of Public Health 2018;28:119–23. Available from: https://doi.org/10.1093/eurpub/ckx067.
- Clements CJ, Cutts FT. The Epidemiology of Measles: Thirty Years of Vaccination. In: Ter Meulen V, Billeter MA, editors. Measles Virus, vol. 191, Berlin, Heidelberg: Springer Berlin Heidelberg; 1995, p. 13–33. Available from: https://doi.org/10.1007/978-3-642-78621-1_2.
- Sathyanarayana Rao T, Andrade C. The MMR vaccine and autism: Sensation, refutation, retraction, and fraud. Indian J Psychiatry 2011;53:95. Available from: https://doi.org/10.4103/0019-5545.82529.
- Burki T. The online anti-vaccine movement in the age of COVID-19. The Lancet Digital Health 2020;2:e504–5. Available from: https://doi.org/10.1016/S2589-7500(20)30227-2.
