Mumps

Synonym:epidemic parotitis

• It can infect any organ but usually affects the salivary glands, and less often pancreas, testis, ovary, brain, mammary gland, liver, kidney, joints and heart.²
• Incubation period is between 14 and 21 days.³ Of those who are infected, 30 to 40% have sub-clinical disease.⁴
• The virus is highly infectious with transmission by droplets spread in saliva via close personal contact.
• Before vaccination, the peak incidence was in late winter or early spring in 3 year cycles.^3,5
• Infected persons excrete the virus for 6 days before symptoms appear and for up to 5 days afterwards.⁶

Initially, virus infects upper respiratory tract and then spreads to draining lymph nodes. This produces viraemia and spreads to many organs.⁴ The ducts in both the salivary glands and seminiferous tubules of the testes are blocked by lymphocytic infiltration and destruction of periductal cells.⁷ Lymphatics surrounding the parotid glands become obstructed producing a gel-like oedema.⁸ The virus may also invade the nervous system and can be detected by EEG and cerebro-spinal fluid (CSF) analysis in 50% of patients, but usually without any signs or symptoms.⁹

Since the introduction of the MMR vaccine, mumps has become a notifiable disease to help monitor the effectiveness of the vaccine. There is a surveillance form for confirmed cases.¹⁰

Either clinical or subclinical infection used to be very common in childhood but with the introduction of the MMR vaccine in 1987, numbers dwindled considerably. However, Health Protection Agency (HPA) statistics show that confirmed cases in England and Wales rose from 94 in 1996 to a projected figure of 43,332 for 2005.¹¹ These statistics suggest that the disease has moved from being almost completely eliminated in the 1990s to making a very significant resurgence. This is thought to be due to parental concern about the link between MMR vaccine and autism, despite Government campaigns to reassure the public that no such link exists.¹²

Typically, there is pain at or near the angle of the jaw and fever may be as high as 39.5°C without rigors in small children. Swelling causes distortion of the face and neck with skin over the gland hot and flushed but there is no rash. With severe swelling, the mouth cannot be opened and is dry because the salivary ducts are blocked. Discomfort lasts for 3 or 4 days but may be prolonged when one side clears and the other side swells. Usually just the parotid glands are involved but rarely, the submaxillary and sublingual salivary glands are affected and this may be difficult to distinguish from inflammation of lymph nodes in that area.

Orchitis⁷

Orchitis may occur 4 or 5 days after the start of parotitis but it often appears without it. This can sometimes lead to the diagnosis being missed.¹³ Orchitis presents with chills, sweats, headache and backache with swinging temperature and severe local testicular pain and tenderness. The scrotum is swollen and oedematous so that the testes are impalpable. The problem is usually unilateral but may be bilateral. Sometimes, as one side resolves, orchitis strikes the other side 3 or 4 days later.

This complication is unusual before puberty but develops in around 40% of cases of mumps in adolescent males. In a third of cases, there is some degree of atrophy of the testicle. There has not been much concern about mumps as a cause of male infertility in the past, although a recent increase in the incidence of orchitis raises the possibility of it becoming a signficant factor.

Meningitis and encephalitis

The great fear of mumps is usually orchitis in adolescent males but meningo-encephalitis is much more serious and affects both sexes. It usually occurs without parotitis. Meningitis is usually mild and self limiting although occasionally there may be transient paralysis of limbs. CSF protein and lymphocytes are increased. With encephalitis, the patient is confused and may lapse into coma and remain so for days, weeks or months. The fatality rate is 2%.¹ A recent outbreak has re-emphasised its importance in the list of differential diagnoses.¹⁴

Mumps arthritis

Arthropathy is an unusual but significant complication.¹⁵ It affects predominantly young men. There is involvement of large and small joints before or after parotitis or in its absence. Fever, leukocytosis, and elevated ESR sometimes accompany a protracted course. The possibility of mumps arthritis should be considered in patients with acute-onset, obscure, or febrile seronegative arthritis.¹⁶

• By far the commonest presentation of mumps is with parotitis. High temperature, pain and swelling in the neck is common with many other infections including tonsillitis, viral pharyngitis and infectious mononucleosis. The tender, swollen parotid glands emerge from behind the ramus of the mandible and can be distinguished from lymph nodes in that on palpation it is not possible to feel in front of the parotid glands.
• HIV infection should be considered.
• Patients with a stone in the parotid duct tend to be older but a much more important feature is that the gland swells and becomes more painful on chewing as saliva is produced.
• Mumps must be in the differential diagnosis of viral meningitis and encephalitis.
• Mumps orchitis typically strikes the same age as torsion of the testis. In torsion, the testis is usually still palpable with the long axis horizontal. There is no pyrexia or other aches and pains.

• In patients with meningitis but without parotitis, the diagnosis may be confirmed by detection of mumps specific antibodies in the serum. Salivary IgM against mumps may be detected. Confirmation of clinical diagnosis by oral fluid testing is offered by the Health Protection Agency.³ Specific antibody levels may not rise for several days and so if the result is negative but clinical suspicion is strong, it is worth repeating the test.
• A rapid real-time test using mumps RNA present in serum has been developed.¹⁸ This is particularly useful if salivary IgM is negative but clinical suspicion is high.
• HIgh resolution and colour Doppler ultrasound has been used to differentiate mumps orchitis from torsion.¹⁹

Non-drug

Keep up fluids and keep the mouth moist.

Drugs

• There is no specific treatment but drugs such as paracetamol and ibuprofen may give symptomatic relief.
• For mumps orchitis, treatment is initially conservative with bed rest, fluids,and scrotal elevation. Analgesia may be required and opiates may be necessary for one or two days if discomfort is severe. Surgical incision into the tunica albuginea to reduce testicular pressure has largely been abandoned. Likewise, oral steroids and adrenocorticotrophic hormones used in the past to reduce inflammation and swelling are now avoided because of evidence that they can induce testicular atrophy. Some authorities recommend broad-spectrum antibiotics to prevent secondary infection.⁷

Although rarely fatal, complications of mumps can include :

• Aseptic meningitis (in 15% of cases, usually without further complications)
• Orchitis, usually unilateral
• Oophoritis may cause pain in 5% of post-pubertal females, sterility seldom occurs
• Profound deafness (in one ear in 1 in 15000 of cases, usually transient)
• Encephalitis (rare, rates reported range from 0.02 to 0.3% of cases)
• Pancreatitis, neuritis, arthritis, nephritis, thyroiditis and pericarditis
• Transient and mild mastitis (uncommon, can occur in either sex)²⁰
• Mild upper abdominal pain (may be related to the pancreas in 50% of cases)
• Mumps in the first trimester of pregnancy may increase the rate of spontaneous abortion, but virus is not teratogenic

Most cases see full recovery. The mortality rate from central nervous system involvement is about 1%. Deaths from other causes are rare, more than half the cases arising in men over the age of 19.

MMR is given in the national immunisation programme at 12 to15 months and at 4 years of age. There is no upper age limit and where required, two doses can be given separated by at least a one month interval. The second dose is especially important for the mumps component as, of the three components, this is the one that is least adequately covered by a single dose.

Evidence of the safety of the MMR vaccine is overwhelming but concordance is best obtained by giving parents an opportunity to voice their fears and offering them factual information. Links to various resources can be found on the NHS immunisation information website. See also Health Promotion for Young Children. Some parents of girls may opt for single vaccines in the belief that the main risk of mumps is orchitis, whereas encephalitis is the greater danger, and affects both sexes equally.