Highlights

Maricopa County health officials have confirmed three new measles cases with no known exposure sources, 12News reported Wednesday, a development corroborated by FOX 10 Phoenix and the Maricopa County Department of Public Health.

The new cases push the county's 2026 total to 10 — the highest in at least 30 years, according to AZ Central. Earlier this year, four cases were linked to a youth basketball game in Mesa; separate exposure sites were also identified in the Queen Creek area, KJZZ reported in April.

The Maricopa County Department of Public Health said community transmission has been confirmed in the county and that it is working with state and local partners on the response. Officials are encouraging residents to confirm they are up to date on measles vaccines and to learn to recognize symptoms.

Why are cases appearing with no known exposure source?

When measles cases surface without a traceable exposure, it typically signals undetected community spread among unvaccinated individuals. The Arizona Department of Health Services called the cases a reminder that measles "can flare among those who aren't vaccinated."

Residents with questions about vaccination status should contact their primary care provider. The county has not announced a timeline for when the outbreak may be declared contained.

Sources

Every factual claim in this article traces to one of the sources below. See how we work for the editorial process.

  1. 12News retrieved 2026-05-07T00:09:14.232138+00:00
  2. AZ Central retrieved 2026-05-07T00:09:14.232138+00:00
  3. kjzz.org retrieved 2026-05-07T00:09:14.232138+00:00
  4. Maricopa County retrieved 2026-05-07T00:09:14.232138+00:00
  5. Maricopa County retrieved 2026-05-07T00:09:14.232138+00:00
  6. AZ Department of Health Services retrieved 2026-05-07T00:09:14.232138+00:00
  7. ein.az.gov retrieved 2026-05-07T00:09:14.232138+00:00

Authored by the_wire. Drafted by AI from primary-source material under our beat-specific editorial guides; reviewed by humans before publish under our five-gate process. Sources retrieved at 2026-05-07T00:09:14.232138+00:00. Every claim traces to a source.