NEW YORK (CBSNewYork) – Health officials in Rockland County say the number of people infected with measles has more than doubled in the last few days.

There are now 33 confirmed cases and doctors say they’re monitoring five other patients who may also have the virus.

There were 15 confirmed cases in Rockland County as of last Tuesday, indicating the disease is spreading.

Previously at schools that have dealt with confirmed cases, students who haven’t received the measles vaccination were ordered to stay home until at least early November.

The initial outbreak was centered in Hasidic communities, including one in New Square, N.Y. Banners and fliers throughout the community are urging people to receive the vaccination.

The vast majority of people are immune from measles after receiving the so-called “MMR vaccine,” but the disease can be highly contagious for the unvaccinated. Classic symptoms include red rash, fever, runny nose, red eyes that become sensitive to light, and coughing.

A quarter of victims wind up in the hospital.

Investigators believe travelers brought the disease from Ukraine, where there’s currently a massive outbreak. From there, they brought it to Israel and eventually New York.

At that time, officials were warning about possible measles contagion from an unidentified traveler at some point between Oct. 4 and Oct. 11:

  • Congregation Bais Elazer in Monsey, N.Y. on Oct. 4
  • Mia’s Reflexology in New City, N.Y. on Oct. 4
  • Lifetime Gym in Montvale, N.J. on Oct. 5
  • Wesley Kosher in Monsey N.Y. on Oct. 5
  • Congregation Borov in Monsey, N.Y. on Oct. 5 and Oct. 6
  • Costco in Nanuet, N.Y. on Oct. 7
  • Care 365 in Monsey, N.Y. on Oct. 8
  • Westchester Medical Center’s Emergency Room in Valhalla, N.Y. on Oct. 11