More than 300 people have been diagnosed with the mumps in suburban New York as the nation's largest outbreak of the disease in years spreads.

A health official says 303 people in the Rockland County towns of Monsey and New Square have been diagnosed with the highly infectious disease. Almost all the cases are among Orthodox Jews.

Investigators say the outbreak started in August 2009 at a Jewish summer camp in Sullivan County with an 11-year-old boy who brought the disease from England.

It has since spread to Jewish communities in Brooklyn, New Jersey and Orange County in upstate New York.

Mumps is spread by coughing and sneezing with the most common symptoms being fever, headache and swollen salivary glands under the jaw.