The new case, at Hempstead Elementary School, is the first case at a public school since the outbreak began in Rockland County in late September.
The East Ramapo School District and the school were notified on Friday by the Rockland County Department of Health, said John G. Lyon, spokesman for Rockland County.
Because the case occurred after the 21 day incubation period had ended so no students will need to be excluded at this time, Lyon said.
"RCDOH instructed the school, through a letter, to monitor the students for signs and symptoms of measles and asked for a list of every student's immunization status," Lyon said. "From previous records, it is known that Hempstead Elementary School has a very high rate of immunization."
To date, 87 cases of confirmed cases of measles have been documented in Rockland County, county health officials said. The outbreak has mainly been focused in private schools located in Spring Valley, New Square, and Monsey.
The outbreak began with visitors to and from Israel in September. Since then the number continues to grow as unvaccinated or under-vaccinated children and adults are exposed, the department said.
Shoppers at the Palisades Center mall and two other businesses in Spring Valley may have also been exposed to the measles over the Thanksgiving holiday weekend when a person measles visited those spots.
More than 6,000 vaccinations have been given since the outbreak began.
Symptoms include a fever, rash, cough, conjunctivitis (red watery eyes) or a runny nose. People are considered infectious from four days before to four days after the appearance of the rash. Symptoms usually appear 10-12 days after exposure but may appear as early as seven days and as late as 21 days after exposure.
For questions regarding measles, call the New York State Department of Health toll-free at 888-364-4837.
Click here to follow Daily Voice Newburgh and receive free news updates.