This illustration, created at the Centers for Disease Control and Prevention (CDC), reveals ultrastructural morphology exhibited by coronaviruses. Note the spikes that adorn the outer surface of the virus, which impart the look of a corona surrounding the virion, when viewed electron microscopically. A novel coronavirus, named Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2), was identified as the cause of an outbreak of respiratory illness first detected in Wuhan, China in 2019. The illness caused by this virus has been named coronavirus disease 2019 (COVID-19). (Courtesy Alissa Eckert, MSMI / Dan Higgins, MAMS via CDC 2019)

The public health departments in San Francisco and Santa Cruz County announced Friday they are aligning with new shortened COVID-19 isolation and quarantine guidelines set by the federal Centers for Disease Control and Prevention.

People who’ve tested positive for COVID-19 are now able to isolate for five days instead of 10 in the two counties if they have no symptoms or if their symptoms are resolving. This assumes they receive a negative test result on, at the minimum, the fifth day of isolation and preferably via an antigen test.

Anyone suffering from an ongoing fever should isolate until symptoms resolve or for 10 days.

Individuals exposed to someone with COVID-19 and who are unvaccinated or are vaccinated but not yet boosted can quarantine for five days instead of 10, assuming they test negative on the fifth day or later, preferably using an antigen test.

For those who are unable to be tested and who are asymptomatic, a 10-day quarantine is required.

Individuals who are fully vaccinated and boosted or are fully vaccinated but not yet eligible for a booster do not need to quarantine following a known COVID-19 exposure unless they exhibit symptoms. It is recommended that a test be taken after five days.

The updated guidelines do not apply to health care workers. Anyone finishing an isolation period should continue wearing a tight-fitting mask around others for 10 days.

Additional guidance for schools is expected to be issued by the California Department of Public Health.

Santa Cruz County schools are offering antigen and PCR testing Saturday at the County Office of Education and Cabrillo College in Aptos from 9 a.m. to 5 p.m. and 9 a.m. to 5 p.m. Jan. 3-7 at those locations plus at the Pajaro Valley Unified School District in Watsonsville.

In San Francisco, guidelines for isolating and quarantining can be found online at https://www.sfdph.org/dph/COVID-19/Isolation-and-Quarantine.asp.

Vaccines remain the best protection against COVID-19, and those ages 5 and older are eligible. Boosters are strongly encouraged for those 16 and older who received their initial vaccines more than six months ago.