(CNN)Up to 20,000 people who attended a religious gathering at a college in Wilmore, Kentucky, in February could have been exposed to a person later diagnosed with measles.
On Friday, the US Centers for Disease Control and Prevention issued an alert to clinicians and public health officials about the confirmed case of measles in an individual present at the gathering who had not been vaccinated against the disease.
"If you attended the Asbury University gathering on February 17 or 18 and you are unvaccinated or not fully vaccinated against measles, you should quarantine for 21 days after your last exposure and monitor yourself for symptoms of measles so that you do not spread measles to others," according to the CDC advisory.
The CDC also recommended that people who are unvaccinated receive the measles, mumps, and rubella (MMR) vaccine.
Reading this news, people may have questions about measles, including its symptoms, infection outcomes and who is most at risk. They may also want to know what makes measles so contagious, what has been the cause of recent outbreaks and how effective the MMR vaccine is.
To help answer these questions, I spoke with CNN Medical Analyst Dr. Leana Wen, an emergency physician and professor of health policy and management at the George Washington University Milken Institute School of Public Health. Previously, she served as Baltimore's health commissioner, where her duties included overseeing the city's immunization and infectious disease investigations.
CNN: What is measles, and what are the symptoms?