CORTE MADERA (CBS SF/AP) — An outbreak at a Conte Madera elementary school began after parents knowingly sent their COVID-19 positive child and a sibling to school last month in violation of isolation and quarantine rules, officials said Saturday.

The child tested positive for the virus during the week of Nov. 8, according to Brett Geithman, superintendent of the Larkspur-Corte Madera School District. Both children continued to attend school the rest of that week and into the following week.

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The child and their sibling, who later tested positive as well, are students in the district’s Neil Cummins Elementary School in Corte Madera.

The parents did not notify the school of the positive test or return multiple calls from public health contract tracers, Geithman said.

The parents could face a misdemeanor charge for violating Marin County’s health order, under which people who test positive for the virus must isolate themselves for at least 10 days.

“Our enforcement team is evaluating the circumstances and will respond accordingly,” Marin County Public Health said in a statement. “Thankfully, this is the only known occurrence of a household knowingly sending a COVID-19 positive student to school.”

On Nov. 18, public health officials contacted the school district after they noticed a discrepancy in records, according to Geithman.

“We noticed you didn’t enter student X into the database” of students with COVID-19, Geithman said district officials were told.

The district immediately contacted the families of students who were exposed and told them to report to the school for rapid testing the next morning.

“We just dropped everything,” Geithman said of he and his staff, who put in an estimated 150 hours after that doing testing, uploading data and contact tracing. “This is a strong reminder that the pandemic is not over, and we have to stay diligent, we have to follow protocols.”

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A total of eight students tested positive: The original student, their sibling, three classmates of theirs who are suspected school-based transmissions and three students who are suspected household transmissions. None of the students experienced serious illness or had to be hospitalized.

“This was elementary school,” Geithman told the Marin IJ newspaper. “They’re kids, playing and having fun together, for seven days with a positive COVID case among them — and there were only three suspected in-school transmissions. What that tells us is that our COVID protocols are working pretty well.”

About 75 students were exposed to the virus from the eight cases, the superintendent said. No staff members tested positive.

Geithman said he did not know whether the original student and their sibling had received any doses of the vaccine.

The district issued a “corrective action” to the family but Geithman said he could not discuss what that was. The superintendent said the family caused a “safety risk” to students, staff and the school community that easily could have spread further over the Thanksgiving break if the exposed families had not been informed.

“This highlights that we are all in this together,” he said. “This is something where, to get through COVID-19, we all have to do our part. Our actions impact the health and safety and wellbeing of others.”

The district reopened for in-person instruction in October 2020 and this is its first case of classroom-based transmission, Geithman

“This one family, as troubling as it’s been, this is not the norm,” he said.

In May there was an outbreak at Our Lady of Loretto School, a private parochial elementary school also in Marin County, linked to an unvaccinated teacher. The teacher would unmask while reading aloud to students — despite an indoor mask mandate — and worked at the school despite a cough, fever and headache until testing positive later.

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Altogether 26 other people — including students and their parents — were infected. A report by the Centers for Disease Control and Prevention, released in August, identified the virus in that outbreak as the delta variant.