Mumps is caused by a single stranded RNA paramyxovirus and is a notifiable disease. Before immunisation most cases were in children aged two to 12 years.
The virus is transmitted through respiratory droplets and initially infects the nasopharynx where replication occurs during the incubation period (18–21 days).
The next stage is a viraemia. Non-specific features commonly seen are low grade fever, malaise, myalgia and headache. The final stage is an inflammatory phase — symptoms are variable and reflect the site of infection. The final stage lasts seven to 10 days and is followed by spontaneous resolution.
Infectivity lasts from the prodromal phase until four days after the onset of the inflammatory phase. However, 20 per cent of patients can have asymptomatic infections.
Features and diagnosis
Parotitis is the commonest symptom in the third stage. It initially presents as tenderness of the parotids followed by unilateral or bilateral swelling and pain, especially with acidic foods. Salivary and submandibular glands can also be swollen and a sore throat is a frequent complaint.
Orchitis may occur in 10–20 per cent of males. It primarily affects post-pubertal males and presents with testicular swelling and pain. Post-pubertal females can get oophoritis, though this is rare (5 per cent).
Before routine immunisation, mumps was a leading cause of meningitis. Five to 15 per cent of cases had this complication. In 40 per cent of these cases meningitis occurs without parotid swelling. Transient sensorineural hearing loss can occur in 4 per cent of adults. Very rarely encephalitis can be present.
Infection during the first trimester of pregnancy leads to an increased risk of spontaneous abortion. There is no link with foetal malformations.
Diagnosis can be confirmed by detection of the virus in either saliva or urine. The virus can be detected from seven days prior to parotitis to nine days after. Blood can be analysed for the presence of IgM or an increase in IgG to mumps antigens. IgM can also be detected in saliva and is the recommended investigation. Ultrasound is a useful tool in excluding testicular torsion.
Treatment and prevention
There is no specific therapy for mumps. The use of immuno-globulin for post-exposure prophylaxis has not been shown to be effective. General measures such as analgesia, anti-inflammatories, salt gargles and soft foods are used. Ice packs and scrotal support are helpful in severe orchitis. Isolation is recommended in the infectious period.
Mumps vaccination was introduced as part of the MMR in 1988 and a second dose was added to the schedule in 1996 between the ages of three-and-a-half to five years. A single dose confers 60–90 per cent immunity and two doses are required for herd immunity.
Soon after the introduction of MMR the incidence of mumps showed a sharp decline. But there has been an increase in cases since 1999 and a sharp increase in 2004. This is thought to be due to a cohort of the population born between 1980 and 1987 not being exposed to naturally occurring mumps but being too old for MMR. Immuni-sation of susceptible adults can be undertaken.
Dr Hashmi is a GP and part-time tutor at St George’s Hospital, south London
Features of mumps
Low grade fever, malaise, myalgia, headache and parotitis.
Orchitis or oophoritis may occur in post-pubertal cases.
Meningitis, hearing loss and hyperglycaemia are rare complications.
Immunisation with MMR is essential.