Israel is in the midst of a mumps outbreak, the Health Ministry announced this week.

Since the beginning of September, 105 people have been diagnosed with mumps, most between the ages of 10 and 24.

During that period in 2008, only four people were diagnosed with the disease, a contagious virus characterized by swollen salivary glands. Only 13 cases were reported for the entire year. In 2007, only six mumps cases were reported.

Eighty-two of the current cases are people from Jerusalem, but the disease has also been found in the central region (11 cases), Tel Aviv (5), the south (4) and Haifa (2).

One of the patients developed testicular infection, a complication of mumps, and is hospitalized in a Jerusalem hospital.

Itamar Grotto, director of Public Health Services in the Health Ministry, believes the increase in the number of cases stems from the fact that the mumps innoculation was added to the national vaccination program only in 1988, along with measles and rubella.

The mumps vaccine is given to children in two doses - at the age of one year and in first grade.

"The outbreak is believed to have occurred among Israelis who didn't get both doses," Grotto said.

Most of the patients are believed to be from communities that refuse to be innoculated, particularly the ultra-Orthodox.

"People who are not innoculated are not exposed to children's diseases, because the population around them has been innoculated. However, they tend to contract these diseases as adults, and at this stage the diseases are more dangerous due to possible complications," said Professor David Greenberg, of the Pediatric Infectious Disease Unit in the Soroka University Medical Center at Ben-Gurion University.

In most cases, mumps runs it course without treatment, but one-tenth of patients develop mild forms of meningitis. In other cases, it could lead to testicular infection or ovarian inflammation. In men it could also lead to deafness or sterility.

The Israel Pediatrics Association called on parents to make sure their children receive both doses of the mumps vaccine, in keeping with the national program.

An increase in mumps cases has also been reported in the United States and Canada. At the end of last week, 15 students at Jerusalem's Or Shmuel yeshiva came down with mumps, apparently after being in close proximity to a student who contracted the disease in Brooklyn.