Mumps

Introduction

Mumps is an acute, generalised viral infection characterised by bilateral parotid swelling.¹

Prior to the introduction of the measles, mumps, and rubella (MMR) vaccine in 1987, it was common in children, but outbreaks are now more common among young adults at university, especially those who did not receive the MMR vaccine.¹

There were over 5000 cases of mumps in England in 2019, more than in any year since 2009.²

Aetiology

Mumps is a viral infection caused by a paramyxovirus, usually affecting children or young adults.¹

Although it can infect any organ, the salivary glands are most commonly affected. Less often affected are the testes, ovaries, pancreas, and brain.¹

Mumps virus is highly infectious and is spread by respiratory droplets and saliva.³

It has an incubation period of 16 to 18 days, and transmission rates are highest one to two days prior to the onset of symptoms. Almost all of those infected subsequently develop life-long immunity.³

Clinical features

15-20% of those infected with the mumps virus are asymptomatic.³

There is usually a prodrome of non-specific, flu-like symptoms which include fever, headache, malaise, myalgia and anorexia.³

Parotitis (swelling of the parotid glands) then develops in 95% of symptomatic cases and usually lasts three to four days, although can last up to ten.^3,1

Mumps is also associated with orchitis and meningitis/encephalitis (see complications section).

Differential diagnoses

High fever with associated neck pain and swelling can be caused by other infections including pharyngitis, tonsillitis, infectious mononucleosis and HIV.¹

Parotid stones can also cause pain and swelling but are usually unilateral and occur in older patients. In this case, chewing causes pain as saliva is produced.¹

Unilateral testicular swelling and pain can be caused by testicular torsion (although here there are no preceding systemic symptoms, and the testicle has a horizontal lie).¹ Bilateral testicular swelling should prompt consideration of epididymo-orchitis caused by sexually transmitted infections.

Meningitis and encephalitis can be caused by other infectious (viral, bacterial, fungal) and non-infectious (neoplastic) agents.⁶ For more information, see the Geeky Medics guide to meningitis. 

Investigations

Mumps is usually a clinical diagnosis, but confirmation (via a salivary sample) is required as it is a notifiable disease.¹ 

Further investigations are also required if patients present with meningitis/encephalitis or orchitis to look for other causes.

Management

Mumps is a self-limiting condition, and most children recover within one to two weeks.^1,3

Supportive management may include simple analgesia (paracetamol and ibuprofen), advice regarding fluid intake and rest.

Admission to hospital is required if there are concerns about complications (e.g. meningitis or encephalitis).³

Children should not attend school for five days following the development of parotitis.³

Vaccination

The MMR (measles, mumps and rubella) vaccination is part of the national immunisation programme. The efficacy of the MMR vaccine (both doses) against mumps is 88%.⁷

If a person is exposed to mumps and has not been fully immunised, MMR should be offered (in the absence of contraindications).³ 

For more information, see the Geeky Medics guides to childhood immunisations and childhood immunisation counselling.

Complications

Orchitis (or epididymo-orchitis)

Mumps orchitis often occurs without parotitis, but if both are present, orchitis generally develops four or five days after the parotitis onset.¹

Orchitis is found in 25% of post-pubertal males with mumps and is bilateral in 15-30% of cases.^1,3

It is associated with severe testicular pain and tenderness. Significant scrotal oedema may make the testes impalpable. Bilateral orchitis may lead to subfertility.¹

Meningitis and encephalitis

Mumps meningitis and encephalitis also usually occur without parotitis.¹

In patients infected with the mumps virus, 15% develop meningism.⁸ Although mumps meningitis is usually mild and self-limiting, mumps encephalitis has a mortality rate of 1.5%.^1,9

Mumps encephalitis is rare, and may present as part of the initial infection, or later in the disease course.¹

Other complications

Other complications include oophoritis, deafness (usually unilateral and transient) and pancreatitis.¹

Key points

• Mumps is an acute viral infection caused by a paramyxovirus, which generally affects children and young adults.
• The clinical presentation is of flu-like symptoms followed by bilateral parotitis. However, 15-20% of those infected with the mumps virus are asymptomatic.
• Mumps is usually a clinical diagnosis, but confirmation (via a salivary sample) is required as it is a notifiable disease.
• Mumps is a self-limiting condition, and most children recover within one to two weeks.
• If a person is exposed to mumps and has not been fully immunised, MMR vaccination should be offered (in the absence of contraindications).
• Complications of mumps include orchitis, meningitis and encephalitis. 

Reviewer

Dr Jennifer Mackintosh

Paediatric registrar

Editor

Dr Chris Jefferies

References

1. Patient.info. Mumps. Last edited September 2020. Available from: [LINK]
2. GOV.UK. Mumps outbreaks across England. Published February 2020. Available from: [LINK]
3. NICE CKS. Mumps. Last revised December 2018. Available from: [LINK]
4. Memorial University Newfoundland. Parotid gland. License: [CC BY-SA]
5. Afrodriguezg. Parotiditis (Parotitis; Mumps). License: [CC BY-SA]
6. Geeky Medics. Meningitis. Last updated October 2020. Available from: [LINK]
7. Harling et al. The effectiveness of the mumps component of the MMR vaccine: a case control study. Published July 2005. Available from: [LINK]
8. Balbi et al. Mumps: Resurgence of a once-dormant disease. Published May 2018. Available from: [LINK]
9. Orlíková et al. Protective effect of vaccination against mumps complications, Czech Republic, 2007-2012. Published April 2016. Available from: [LINK]