Mumps is an acute viral illness characterised by swelling of the parotid glands, which may be unilateral or bilateral. It can cause permanent unilateral deafness at any age. The incubation period is 14-21 days. Before vaccination, mumps was a common cause of viral meningitis. Now the vaccine is given as part of the triple MMR (mumps, measles, rubella) vaccine, introduced in 1988, the same year that mumps became a notifiable disease.