State officials are continuing to implore health care providers to administer an extra dose of the mumps vaccine to patients before the holiday season.

State Epidemiologist Sarah Park issued a second notice Monday, six weeks after initially notifying primary care physicians, emergency and urgent care doctors and nurses of the need for an additional mumps vaccination due to an outbreak that has grown to 557 confirmed cases from 384 at the end of September.

“This number likely underrepresents the true number of those infected,” Park wrote in the medical advisory, adding that nearly two-thirds of cases are among adults. “With the holidays rapidly approaching and our investigations indicating persistent disease activity, the DOH recommends administering an outbreak … dose to all persons now to help curtail this outbreak as well as improve protection against mumps disease and its related complications.”

There have been at least a dozen reports of orchitis — inflammation of one or both testicles caused by the virus — and four cases of hearing loss, she said, though symptoms are mild to moderate in severity for most patients.

The DOH has advised anyone who lives or works in crowded conditions to get another dose to stem the outbreak of the contagious viral disease spread by coughing, sneezing and touching infected items, such as cups and utensils. Symptoms of mumps resemble the flu and include fever, headache, fatigue, loss of appetite and swollen salivary glands near the jaw.

The “outbreak dose” is recommended for adolescents and adults born in 1957 or later who had two doses of the vaccine 10 or more years ago, while those with one dose five years or more ago should receive a second dose. The DOH recommends people who do not know whether they had the disease or were ever vaccinated to also get an extra shot.

The Health Department is urging people with suspected mumps not to go to school, work or public places and to wear a mask and avoid close contact with others.