Excitement about last month’s captivating, multiday worship service at Asbury University turned to anxiety this week for some participants after the Centers for Disease Control and Prevention and Kentucky health officials announced that someone with measles had attended the event.

Measles is a “highly contagious virus” that spreads through the air, The Washington Post reported. Americans are generally vaccinated against it during childhood, but outbreaks can quickly turn deadly for the small share of adults who are not.

“Community transmission of measles in connection with (the Asbury revival) is possible, particularly among unvaccinated or undervaccinated individuals,” said CDC spokesman Scott Pauley in a statement, according to CBS News.

He and other health officials urged unvaccinated or undervaccinated people who took part in the revival on Feb. 17 or 18 to contact their doctor whether or not they’re feeling sick.

“Vaccines or immunoglobulin can be administered following exposure ... to fend off the virus,” CBS News reported.

This week’s news of the potential measles outbreak called to mind church-focused headlines during the early days of the COVID-19 pandemic, when faith leaders were encouraged, if not required, to suspend in-person gatherings due to infection risk.

As the Deseret News reported at the time, worship services are vulnerable to illness outbreaks, since participants typically engage in a variety of germ-spreading behaviors, from singing, to hugging, to sharing cups during communion rituals.

“People shake hands, introduce themselves and share what’s going on in their lives. There’s ample opportunity for germs to be spread,” said the Rev. Tim Briggs to the Deseret News in March 2020.

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In addition to involving some of these typical faith-related activities, the Asbury revival brought many, many people together in a relatively small space. Thousands of people from across the country and even some international travelers stood in line and then sat side-by-side as they took part in the worship services.

The student-initiated revival began on Feb. 8, when a few students stuck around after an on-campus chapel service and continued worshipping together into the night, as the Deseret News previously reported. The Asbury outpouring, as it’s also been called, ended on Feb. 23 with a final student-focused service.

The CDC has estimated that around 20,000 people were involved in the revival on the days the infected person was present, CBS News reported.

As of Thursday, it was unknown whether any other revival participants were showing measles symptoms, according to The Washington Post.

“Early symptoms of measles can include fever, cough and runny nose, followed by a rash three to five days after symptoms begin,” the article said.

In a Feb. 24 statement, leaders from Asbury University said the school is cooperating with local health officials.

“Asbury University is working with (Jessamine County Health Department) officials to ensure all precautions are taken to mitigate any further spread,” the statement said.