county first to use rapid DNA-based beach water testing to protect public | News


San Diego County this week became the first coastal county in the nation to begin using rapid DNA-based seawater testing technology that will produce faster results and earlier warnings to protect swimmers. when bacteria levels reach unhealthy levels in seawater.

County Board of Supervisors Vice Chair Nora Vargas, County Public Health Officer Dr. Wilma J. Wooten, officials from the County Public Health Laboratory, its Department of Health and Quality of environment and others gathered Wednesday morning near the Imperial Beach pier for the announcement.

Vargas said the county plans to expand its use Thursday of DNA-based digital polymerase chain reaction — ddPCR — testing technology to more than 70 miles of shoreline that the county routinely samples and tests to protect the audience.

The new system will allow the county to sample beach water in the morning, get results and notify the public in the afternoon instead of the next day.

Officials said the DNA-based system is also more sensitive to bacteria levels than the older method, which required growing bacterial cultures from water samples in petri dishes.

“I am pleased to announce that with today’s sampling, San Diego becomes the first coastal county in the nation to implement the ddPCR method for beach water sampling,” said Vargas. Wednesday to applause.

“Faster results,” she said, “will allow the county to issue or lift beach advisories the same day samples were collected. And it reduces the time that the public might unknowingly be in danger and…when the water is contaminated.

The county and state public health lab conducted a side-by-side study comparing DNA testing to the petri dish system in 2019.

The California Department of Public Health gave the new system final lab approval in February, paving the way for the county to expand its use of the process.

For more information about the county’s beach water quality testing program and to check local conditions, visit the county’s “Check In Before You Get In” website at


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