Mumps is an acute, generalised infection caused by a paramyxovirus, usually in children and young adults.
- It can infect any organ but usually affects the salivary glands and, less often, the pancreas, testis, ovary, brain, mammary gland, liver, kidney, joints and heart.
- The incubation period is between 14-25 days (average 17 days).
- The virus is highly infectious with transmission by droplets spread in saliva via close personal contact.
- Infected persons excrete the virus for several days before symptoms appear and for several days afterwards.
Since the introduction of the measles, mumps and rubella (MMR) vaccine, mumps has become a notifiable disease to help monitor the effectiveness of the vaccine.
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. Since 2004, the majority of the confirmed cases have been linked with outbreaks in universities. Many confirmed cases were still unvaccinated or had only received one dose of the MMR vaccine.
There were around 6,758 cases in total in 2013 in England but this remains well below figures seen in the mumps epidemic in 2005 when the figure for England and Wales was 43,378.
- Mumps can be asymptomatic.
- Nonspecific symptoms lasting a few days, such as fever, headache, malaise, myalgia and anorexia, can precede parotitis.
- Parotitis is usually bilateral although it can be unilateral.
- Typically, there is pain at or near the angle of the jaw.
- 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 three or four 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.
- Orchitis may occur four or five days after the start of parotitis but it often appears without it. This can sometimes lead to the diagnosis being missed.
- 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.
- Orchitis is usually unilateral but may be bilateral.
- Sometimes, as one side resolves, orchitis strikes the other side three or four days later.
- Orchitis occurs in around 25% of postpubertal men.
- Subfertility following bilateral orchitis is rare.
Meningitis and encephalitis
- Mumps frequently affects the nervous system.
- Meningism occurs in around 15% of patients.
- It usually occurs without parotitis.
- Meningitis is usually mild and self-limiting.
- Mumps encephalitis may present early by direct invasion following initial infection, or late as a post-infectious event.
Although rarely fatal, other complications of mumps can include:
- Oophoritis, which may cause pain in 5% of postpubertal females; sterility seldom occurs.
- Profound deafness (in one ear in 1 in 15,000 of cases, which is usually transient).
- Pancreatitis occurs in around 4% of cases.
- Mild upper abdominal pain (may be related to the pancreas in around 50% of cases).
- Neuritis, arthritis, nephritis, thyroiditis and pericarditis have all been reported.
- Transient and mild mastitis (uncommon – can occur in either sex).
- Mumps in the first trimester of pregnancy may increase the rate of spontaneous abortion but the virus is not teratogenic.
- By far the most common presentation of mumps is with parotitis. High temperature, pain and swelling in the neck are 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 and there are no other aches and pains.
- In most cases, the diagnosis can be made clinically. However, since the introduction of the MMR vaccine, all cases require laboratory confirmation. If a diagnosis of mumps is considered likely, notify the local HPU, which will arrange for an oral fluid sample to be collected for confirmation of the infection.
- In patients with meningitis but without parotitis, the diagnosis may be confirmed by detection of mumps-specific antibodies in the serum. Salivary immunoglobulin M (IgM) against mumps may be detected. As with mumps parotitis, the local HPU will arrange oral fluid testing. 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.
- Real-time reverse transcriptase polymerase chain reaction tests (RT-PCR) and mumps genotyping are useful in cases where mumps occurs in immunised patients.
- High-resolution colour Doppler ultrasound has been used to differentiate mumps orchitis from torsion.
Keep up fluids and keep the mouth moist.
- 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 analgesia.
Most cases see full recovery. About 1 in 1,000 people with mumps meningitis develop encephalitis, of whom1.5% of cases are fatal. Deaths from other causes are rare, more than half the cases arising in men over the age of 19 years.
- MMR vaccine is given in the national immunisation programme (see separate Measles, Mumps and Rubella (MMR) Vaccination article).
- Normal hygiene measures to prevent droplet infection should be instituted in the household of a patient who has mumps.
- Children should be excluded from school for five days following onset of parotid swelling.