California is only state in CDC's third-lowest tier for COVID-19 spread: Where does Bay Area stand?

California was the only U.S. state in the yellow tier Tuesday morning in the Centers for Disease Control and Prevention's COVID Data Tracker.

The CDC's tracker uses the latest data to report on the severity of the COVID pandemic in each state. The yellow level indicates "moderate" community transmission of the coronavirus with 10 to 50 total new cases per 100,000 people in the past 7 days fall here. Puerto Rico was also in the yellow.

Most other states across the country were in the red tier indicating "high" transmission with more than 100 total new cases per 100,000 in the last week. Florida, Georgia, Illinois, Louisiana, Connecticut and Mississippi were all in the orange, signaling "substantial" community transmission.

The CDC's tracker also assigns tier levels to counties in all 50 states, and counties in the Bay Area were generally seeing lower community transmission than the rest of the country. Contra Costa, Napa, San Francisco, Santa Clara, Solano, Sonoma were all in the orange on Tuesday. Alameda, Marin, San Mateo were in the yellow.

Eight counties — all except Solano — in the Bay Area are using the tier levels as one factor in determining whether a county can fully lift its mask mandate.

A county must reach the "moderate" (yellow) tier of case rates, as determined by the Centers for Disease Control and Prevention's data tracker, and remain there for three weeks.

The counties set two other criteria to lift the mask mandate. One, 80% of a county's total population must be fully vaccinated against COVID-19, or eight weeks removed from when the COVID-19 vaccine has been authorized for children ages 5 to 11. Marin is the only county in the Bay Area to meet this criteria and as of Tuesday 81% of its population was fully vaccinated.

Secondly, a county's health officer must determine that COVID-19 hospitalizations are "low and stable." In Marin, the only county that's close to meeting the criteria to end the mandate, Dr. Matt Willis, the county's health director has set the metric for when hospitalizations are at a point where it's safe to end the mask rules..

"Last week, there were 15 total COVID-19 hospitalizations in Marin," Willis said last week. "So we set that as the metric — we'll want to see less than 15 people in the hospital for COVID-19 before lifting the mandate."