Health officials in California are warning the public that an individual with a confirmed case of measles may have exposed visitors of Disneyland to the contagious virus. In a new bulletin by the Los Angeles County Department of Public Health, officials are warning anyone who visited the park on October 16th that they may have come into contact with the infectious illness.

The individual is believed to have visited the park for the majority of the day, with health officials saying that the person was at Disneyland between 9:15 a.m. and 8:35 p.m. on that day. The person also visited a nearby Starbucks location at around 7:50 a.m. on that same day.

Health experts are taking a proactive approach to the situation in the hopes of warding off an outbreak of measles. Misguided or willfully ignorant anti-vaccination proponents have increased the risk of such an outbreak, and officials are urging anyone who visited the park or Starbucks location on October 16th to contact their doctor if they are not already vaccinated. This is especially important for women who may be pregnant or individuals who have immune system disorders.

“For those who are not protected, measles is a highly contagious and potentially severe disease that initially causes fever, cough, red, watery eyes, and, finally, a rash,” Los Angeles County Health Officer Muntu Davis said in a statement. “Measles is spread by air and by direct contact even before you know have it. The MMR immunization is a very effective measure to protect yourself and to prevent the unintentional spread of this potentially serious infection to others.”

The MMR vaccine, which protects against measles, mumps, and rubella, is highly effective and incredibly safe. Adverse reactions are rare and almost always minor in nature, and the vaccine was credited with eradicating measles in the United States as recently as the year 2000. Recent outbreaks of the disease have popped up exactly where you’d expect: anti-vaccination hotspots.