Health bosses are warning people to get themselves vaccinated after cases of mumps rocketed by more than 50% in a year.

Those most at risk are young adults too old to have had a routine measles, mumps and rubella (MMR) vaccination as children.

The number of cases have been rising because those at risk are often in college or university.

When a large number of people live in semi-closed institutions, it allows the disease to pass more easily from person to another.

As the susceptible group is a large one, the number of cases is expected to continue to grow over the next few years.

There are also concerns that children whose parents chose not to let them have the MMR jab because of fears it could cause autism, may also be at risk.

There were 139 confirmed cases of mumps across Sussex in 2009, with 70 in West Sussex, 42 in East Sussex and 27 in Brighton and Hove.

In 2008 the total was 88 and so far this year there have been 12 cases.

The sharp increase is mainly down to an outbreak of mumps at the University of Chichester at the start of 2009, which led to dozens of students being sent home after falling ill.

Before the introduction of the MMR vaccine in 1988, mumps was a common childhood infection that was responsible for 1,200 hospital admissions a year in England and Wales.

After the MMR vaccine was introduced as part of the routine childhood vaccination programme, the number of mumps cases fell sharply, with less than 100 cases reported in 1996.

However, in recent years, there has been a surge in the incidence of mumps, and in 2005, there was a mumps epidemic that resulted in more than 43,000 cases in England and Wales.

Complications of mumps can include sterility in men, meningitis and deafness.