Mumps

Mumps is an acute infectious disease caused by a paramyxovirus characterised by bilateral parotid swelling. It is spread by respiratory droplets, fomites or saliva, and replicates mainly in the upper respiratory mucosa. The incubation period of mumps is 16-18 days (range 12–25 days). It is most infectious from around 1–2 days before onset of symptoms, to about 9 days afterwards, although it may be asymptomatic in 15–20% of people. Nearly all people develop life-long immunity to mumps after one episode of infection.

Diagnosis

• Consider a diagnosis of mumps in people presenting with parotitis (swollen parotid glands) — this is present in 95% of symptomatic cases.
  • Typically, one parotid gland is affected first, reaching a maximal size after 2–3 days, with the other gland closely following it. About a quarter of affected people have unilateral parotitis.
  • The ear lobe over the affected gland may be deflected upward and outward, and the angle of the mandible may be obscured (this does not occur with cervical adenopathy).
  • The affected gland may be tender to touch.
  • During the period of gland enlargement, the person may complain of earache, and have difficulty with pronunciation of words or chewing.
• Non-specific symptoms (which may precede parotitis), include low-grade fever, headache, earache, malaise, muscle ache, and loss of appetite — typically occur 1 day before overt signs of parotitis and peak around the time the parotid glands are most swollen.
• Consider the likelihood of mumps:
  • Mumps is unlikely in people who have been fully immunised. Younger people who have not received two doses of the combined measles, mumps, and rubella (MMR) vaccine are most at risk.
  • Mumps is unlikely in people who have previously had mumps.
  • Mumps is likely if patient has had significant contact with someone with mumps (significant contact is considered as being in the same room for 15 minutes or more, or face-to-face contact) or if there has been a recent outbreak.
  • Mumps is unlikely in infants aged under 1 year.
• The diagnosis of mumps is usually clinical and is confirmed by laboratory analysis of a saliva sample to detect presence of immunoglobulin (Ig)M mumps antibody.

Differential Diagnosis

• Other infectious causes that may present with parotitis:
  • Viral infections, such as Epstein–Barr (the virus that causes mononucleosis), parainfluenza, adenovirus, influenza type A, coxsackievirus, parvovirus B19 (the virus that causes erythema infectiosum, also known as slapped cheek syndrome), lymphocytic choriomeningitis virus, and HIV
  • Suppurative bacterial infections, including Staphylococcal aureus and atypical mycobacteria (for example tuberculosis)
• Non-infectious causes of parotitis:
  • Parotid duct obstruction (for example, salivary stones, cysts, tumours)
  • Prescription drugs (for example thiazide diuretics, phenothiazines, thiouracil, iodide contrast media)
  • Metabolic disorders (for example diabetes mellitus, cirrhosis, uraemia)
  • Autoimmune disease (for example sarcoidosis, Sjogren's syndrome, Wegener's granulomatosis)

Management

• Mumps is a notifiable disease; if there is any suspicion of infection, notify the local Health Protection Unit (HPU), and they will arrange a testing kit for confirmation and surveillance purposes (usually oral fluid swab).
• Advise the patient that mumps is usually a self-limiting condition which will resolve over the course of about 1 - 2 weeks, with no long-term consequences, and that antibiotics are not required.
• Advise to rest, to drink adequate fluids, to apply warm or cold packs to the parotid gland and to take simple analgesia as required.
• Advise to stay off school or work for 5 days after the initial development of parotitis.
• Advise the person to seek medical advice if they develop symptoms of meningitis or epididymo-orchitis.

Complications

Mumps is usually a self-limiting disease that resolves within 1–2 weeks, and most people recover without any long-term complications. Complications include:

• Parotitis (inflammation of the parotid glands) usually resolves without complications, however:
  • The submandibular and sublingual salivary glands are also affected in about 10% of people with mumps, usually in conjunction with bilateral parotitis. This may cause obstruction of lymphatic drainage in the neck, resulting in presternal oedema in about 6% of affected people and (rarely) supraglottic oedema.
  • Persistent dilation of the salivary ducts (sialectasia) leading to their chronic inflammation (sialadenitis) has been rarely reported.
• Epididymo-orchitis — the most common complication affecting up to 38% of men. Mumps epididymo-orchitis can result in testicular atrophy and subfertility.
• Encephalitis — occurs in about 0.1% of people.
• Oophoritis — reported in about 7% of women with mumps, but rarely causes infertility or premature menopause.
• Aseptic meningitis — occurs in up to 25% of people with mumps, and is three times more common in males. Mumps meningitis is usually benign, and almost all patients have a complete recovery.
• Transient hearing loss — affects about 4% of people, but permanent deafness is much less common.
• Myocardial complications — ECG changes, including ST segment depression, T wave inversion, and prolonged PR intervals, are seen in 15% of mumps infections.
• Pancreatitis — affects about 4% of people, but is usually mild and transient.
• Rarer complications of mumps that have been reported include other central nervous system disorders (such as cerebellar ataxia, facial palsy, transverse myelitis, and Guillain–Barre syndrome), thyroiditis, mastitis, prostatitis, hepatitis, and thrombocytopenia.

Prevention