Delaware County wastewater samples test positive for measles. So far, no person has a confirmed diagnosis of the disease

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Two wastewater samples from the DELCORA Western Regional Treatment Plant in Chester tested positive for measles, the Delaware County Health Department announced Wednesday.

However, Delaware County officials have yet to identify someone with a confirmed case of the disease.

DELCORA collects and treats wastewater for approximately 500,000 people, including 46 municipalities in Delaware and Chester counties. DELCORA participates in the WasterwaterSCAN project, which is run by Stanford University.

The first detection was from a positive sample collected June 9. The second positive sample was collected June 11. The Delaware County Health Department is coordinating with the Pennsylvania Department of Health and other partners to monitor the virus.

Measles cases are on the rise nationwide. Pennsylvania has already surpassed last year’s infection total of 16 cases.

As of Wednesday, the Pennsylvania Department of Health has tallied 67 cases of measles in 2026. An ongoing outbreak in Lancaster County is causing some concern. On Friday, the state Department of Health issued an exposure notice for visitors of the Lancaster County Courthouse.

Delaware County health officials are urging unvaccinated residents to get the MMR vaccine, for measles, mumps and rubella, which has been readily available in the country since the 1970s. The extremely contagious disease can also be fatal. Babies, children, pregnant women and people who are immunocompromised are most at risk of serious complications.

As of June 11, the U.S. Centers for Disease Control and Prevention has confirmed 2,063 measles cases in 40 states. There have been a total of 30 new outbreaks in 2026, with 93% of cases directly associated with outbreaks. With 2,263 measles cases confirmed in 2025, it is likely the 2026 case total will surpass last year’s figure.