Maricopa County Faces Largest Measles Outbreak in Decades Amid Low Vaccination Rates
Maricopa County, Arizona, is experiencing its most significant measles outbreak in 30 years, with 15 confirmed cases reported in 2026. The outbreak has been traced back to exposure events at the Arizona Athletic Grounds in southeast Mesa, occurring on April 23 and between May 5-7. Health officials are alarmed by the transmission of the measles virus, particularly as vaccination rates in the Phoenix metro area have fallen below 90 percent. Dr. Wassim Ballam, chief of infectious diseases at Phoenix Children’s Hospital, emphasized the importance of vaccination, noting the vaccine's efficacy of over 95 percent with two doses. The Centers for Disease Control and Prevention had previously considered measles virtually eradicated in the U.S. Dr. Nick Staab, Maricopa County’s chief medical officer, warned that the low immunization rates could lead to sustained transmission, affecting both children and unvaccinated adults.