A local coronavirus surge fueled by the omicron variant has been declining since its peak on Jan. 9, Marin County’s public health officer said Wednesday.

Dr. Matthew Willis said the average daily new infection count on Jan. 9 was 407 cases over a seven-day period. On Wednesday, the number was 280.

Willis said the county “didn’t see a spike” on Tuesday, when people returned to schools and work after the three-day Martin Luther King Jr. holiday weekend.

“The case rate has been steadily declining each day since Jan. 9,” Willis said. “It’s the lowest it’s been since Dec. 29.”

Also, he said, analyses of the county’s wastewater indicate a decrease in concentration of the virus.

“We’re seeing promising signs from the case counts and the wastewater surveillance that the peak is behind us,” Willis said.

There was a one-day high count of 625 positive cases on Jan. 4, but Willis said the county uses the seven-day rolling average to determine where it stands.

The update comes as Marin officials notified parents that COVID-19 exposure notices will now only be sent out in the instance of known exposures from close contacts.

Previously, the county had sent out notices for every reported exposure — with some parents getting four or more notices a day.

“Local case investigations have shown that most COVID infections among students and staff occur outside of school, and are from household exposures, private indoor gatherings and higher-risk activities, including sports,” Dr. Lisa Santora, Marin deputy public health officer, said in a letter to parents last week.

“For these reasons, Marin County Public Health recommends suspending notification for low-risk classroom exposures,” she said.

Santora said the county “does not recommend testing all students and staff who have been exposed in classroom settings.”

Willis said Wednesday that for all Marin residents, the “safest assumption is ongoing exposure.” People in general need to “monitor for symptoms and test if symptoms develop, and if positive, then isolate,” he said.

In schools, Santora said, “students and staff who are known close contacts or who have been exposed in higher-risk activities should test on day 5 after their last exposure — or sooner if they develop symptoms.”

Santora said that even though one in 20 or 25 people in the county is infected with COVID-19, “fewer than one in 1,000 infected Marin residents is hospitalized,” she said.

“Schools remain among the safest places for children,” she said.

Marin school districts and community colleges reacted this week to the county’s updated guidance.

At College of Marin, officials announced Wednesday they will postpone the start of in-school instruction to Feb. 7 to allow for the omicron surge to decline further.

David Wain Coon, the college president, said it would continue with remote instruction until then.

“This decision was based on the most recent data from Marin Health and Human Services and the Centers for Disease Control and Prevention,” Wain Coon said in a memo to staff and students. “The Bay Area is currently experiencing impacts from the Omicron variant and a surge in cases.”

Also, the college will be acquiring additional N95 masks and increasing testing.

“By Feb. 7, the college will also be equipped with 60,000 N95 masks that will be distributed to both students and employees,” Wain Coon said

Free at-home rapid COVID-19 tests are now available from the federal government at covidtests.gov. Updated Marin schools guidance on testing, quarantines and isolation is available at marinschools.org.