Public health officials in Maricopa County say Mesa is now experiencing the region’s largest measles outbreak in decades, raising concerns among doctors and health experts as confirmed cases continue increasing across the Valley.
According to county health officials, Maricopa County has confirmed 15 measles cases so far in 2026, making it the most significant outbreak the area has seen in roughly 30 years. Health leaders say the current outbreak includes at least 11 potential public exposure events connected to recent measles transmission that began in late April.
Officials traced two major exposure events to the Arizona Athletic Grounds complex in southeast Mesa. The first exposure reportedly occurred on April 23, while another series of exposures happened between May 5 and May 7. Maricopa County health officials said a complete list of possible exposure locations has been published online so residents can determine whether they may have been exposed to the virus.
Measles is considered one of the world’s most contagious viruses. Doctors say symptoms often begin with a high fever, cough, runny nose, and watery or red eyes before the illness develops into the distinctive rash commonly associated with measles infections.
Dr. Wassim Ballam, chief of infectious diseases at Phoenix Children’s Hospital, said medical professionals are extremely concerned because measles is now spreading within the community rather than remaining isolated to a single imported case. Ballam warned that vaccination rates across parts of the Phoenix metro area have fallen below 90%, creating conditions that allow outbreaks to spread more easily.
Ballam also noted that measles had once been considered virtually eliminated in the United States due to widespread vaccination efforts. He stressed that vaccination remains the most effective defense against infection and said the measles vaccine is more than 95% effective after two doses.
Health officials are urging parents to verify that their children are fully vaccinated and are also reminding adults to confirm their immunization status if they are unsure whether they previously received the recommended measles, mumps, and rubella vaccine series.
While measles is often associated with young children, doctors say unvaccinated adults are also vulnerable to infection and serious complications. Dr. Nick Staab, Maricopa County’s chief medical officer, warned that current vaccination levels may not be high enough to stop continued community transmission.
Staab described the outbreak as unusually large for Maricopa County and said local health officials have not faced a measles outbreak of this size in a very long time. He explained that lower immunization rates increase the possibility that the virus could continue circulating throughout the community.
For residents who choose not to receive the vaccine, health officials recommend closely monitoring for symptoms and isolating immediately if symptoms appear. Staab advised anyone who may develop measles symptoms to remain isolated for at least 14 days in order to reduce the risk of infecting others.
The outbreak in Mesa comes as measles cases have increased nationally in recent years. Public health experts across the country have raised concerns about declining vaccination rates and the growing risk of outbreaks in communities with lower immunization coverage.
County health officials continue investigating possible exposure sites and encouraging anyone who may have been exposed to contact healthcare providers if symptoms develop. Officials say measles can spread rapidly through coughing, sneezing, or simply being in the same area as an infected person because the virus can remain in the air for extended periods of time.
Source: ABC15 Arizona
