The number of mumps cases so far this year is already set to outstrip figures for the whole of last year.

Health chiefs blamed the worrying rise on adults who are too old to have been immunised contracting the disease.

They claimed the frequency of mumps cases would continue to climb over the next few years.

There have already been 82 confirmed incidents across Sussex this year.

This is only slightly fewer than the 88 cases recorded for the county for the whole of 2008.

Between January and March there were 69 cases in West Sussex, five in Brighton and Hove and eight in East Sussex.

Last year there were 49 incidents in West Sussex, 19 in Brighton and Hove and 20 in East Sussex.

The Health Protection Agency (HPA) said the unexpectedly high number was down to an outbreak of mumps at the University of Chichester earlier this year when dozens of students had to be sent home after falling ill.

There have been no new cases at the university for several weeks.

Mary Ramsay, who monitors mumps cases at the HPA, said: “The increased occurrence of the disease is mainly among older teenagers and young adults in their early 20s and mostly among those in further or higher education establishments.

“Some in this age group were too old to be routinely given the measles, mumps and rubella vaccine when it was introduced in 1988.

“The number of cases has increased more steeply in recent years because many of the young adults in this cohort are now at university or in further education colleges.

“This large number of people in semi-closed institutions allows the disease to pass more easily from one person to another.

“As the susceptible group is quite large we expected to see high numbers of cases to continue over the next few years.”

Dr Ramsay did not believe the recent rise was linked to the controversial MMR jab and its now discredited link with autism.

The HPA recommends that school leavers and other young adults who have not received MMR or who only received one dose should make sure they are vaccinated properly.