Mumps as a cause of admission to hospital: an estimate for Western Australia 1981.

Close to 40% of children admitted to Princess Margaret Hospital with mumps over the period 1979 to 1982 were diagnosed retrospectively as a result of virological tests and their illness was not coded as being due to mumps. This clinical underestimate of the incidence of mumps is due to the frequent absence of salivary gland enlargement, especially in preschool children. In such cases there is usually evidence of inflammation of the upper respiratory tract. The main clinical features leading to admission were neck stiffness, fits and high fever. An appropriate adjustment was made to the figures obtained from the computerised data on discharges with the diagnosis of mumps from Western Australian hospitals in 1981. This led to the estimate that 104 patients suffering from mumps were discharged from hospital during that year. It was also estimated that mumps was responsible for 379 in-patient days. Our findings show that the benefit cost ratios for mumps immunization of others are underestimates.