(Credit: Jonathan Tichler / Met Opera)

Following a performance of “La Bohème” on April 25, the Metropolitan Opera House sent out an email to audience members who attended the performance advising that one of their fellow patrons had contracted measles.

According to The Gothamist, the person visited the Metropolitan Opera and at least one Manhattan restaurant while infected with measles, prompting an effort by the New York City health department to alert anyone who may have been exposed. The letter advised attendees of that evening to get vaccinated against measles if they weren’t already and to keep an eye out for potential symptoms.

According to the U.S. Centers for Disease Control and Prevention, it typically takes 11 to 12 days for symptoms to appear after exposure to the measles, and the virus can be contagious up to four days before a rash shows up.

According to Health officials, a total of six measles cases have been confirmed in New York City and were all linked to international travel. Statewide, there have been 10 confirmed cases, including one reported in an unvaccinated child under five in Nassau County.