BRENTWOOD, Calif. (KRON) — An East Bay school district has confirmed at least 15 positive COVID-19 cases among its students and staff just three days into the new school year of in-person learning.

The cases were found throughout all of the Brentwood Union School District’s 11 schools.

The district says this does not necessarily mean that students and staff got the virus at school. Contact tracing has shown that the people who tested positive did not get it from another person at school, officials said.

However, the Contra Costa County Health Department has told the school district that they should expect to see more positive cases in our schools.

The district says they are doing everything to prevent a spread of positive cases at school, including mask wearing indoors regardless of vaccination status, hand washing and sanitization protocols.

When a school gets a positive case, contact tracing begins, then everyone exposed is notified and told to quarantine. Any impacted classroom is cleaned thoroughly and all school staff and families are notified.

With these protocols in place, for now it seems the schools will remain open.

District officials say they hope people stay home when sick and get vaccinated if they haven’t already. Children under the age of 12, however, are not authorized to get the COVID-19 vaccine at this time.