Highlighting the threat that coronavirus poses to basic public health systems around California and the nation, a worker at San Jose’s wastewater treatment plant — a facility that treats the sewage from 1.5 million people in San Jose and seven other cities — has tested positive for COVID-19.

The employee is a janitor working as part of a contract company. The massive plant, located in Alviso, has 17 employees in self-quarantine as a result and is running at about 70% staffing.

“The staff is continuing with business as usual, although at a lower head count,” said Kerrie Romanow, director of environmental services for the city of San Jose. “We are continuing to treat wastewater.”

Romanow said Monday that plant operators — employees who have state licenses and who run pumps, filters, chlorination equipment and other systems to treat 100 million gallons of wastewater a day before releasing it into San Francisco Bay — are working in shifts so that they aren’t all together at the same place and time.