California has been locked down in some form for six months now, and many Bay Area counties remain under the most severe restrictions of Gov. Gavin Newsom’s new, phased economic reopening plan.
In the latest update Tuesday, Sept. 15, four of the nine counties that make up the Bay Area had advanced from the first tier, indicating “widespread” transmission, into the second tier, or “substantial” transmission: San Francisco, Santa Clara, Napa and Marin, which earned Tier 2 status this week. Alameda, Contra Costa, San Mateo, Solano and Sonoma counties remain stuck in Tier 1, along with the majority of California’s population.
There are four tiers — ranging from widespread to moderate — with corresponding colors (purple, red, orange, yellow) and two all-determinative metrics: the per-capita case rate and the positivity rate for PCR tests, both averaged over seven days. A third figure — the number of tests per-capita — can lower a county’s case rate in the state’s formula from between 12% and 40%. The state will update its figures every Tuesday; if a county has spent the minimum three weeks in one tier and met both marks for the next one for 14 days, it is eligible to move on in the next update.
With each step up, indoor capacity increases. Once a county reaches the second tier, most sectors are eligible for some form of reopening, but stricter local orders, like those in San Francisco and Santa Clara, take precedence.
Read more about the new plan — and what it means for restaurants, offices, schools and more — here.
While the state updates its tiers every Tuesday, with data delayed by about two weeks, we’re tracking the progress of all nine counties in the Bay Area in real-time. According to our data, Alameda County has joined San Francisco, Santa Clara, Napa, and Marin counties in meeting both Tier 2 thresholds. San Mateo, Contra Costa and Solano counties have positivity rates eligible for Tier 2 but their case rates remain too high. Sonoma is the only Bay Area county not meeting either measure, according to our data.
Since Newsom announced the system Aug. 28, 10 counties, including Santa Clara and Marin, have moved from Tier 1 to Tier 2. In total, there are 30 counties in the most severe grouping and 17 counties in Tier 2. Another nine are in Tier 3, and two remote mountain counties — Alpine and Modoc — are in the lowest of the four tiers.
The next update, Tuesday, Sept. 22, will be the first time counties are eligible to move between the second, third and fourth tiers because of the three-week minimum at each tier. Dr. Mark Ghaly, the state’s top health official who delivers the updates, said he anticipates “some movement among counties in those tiers.”
Note: CDPH dates cases to its earliest known infection and uses a seven-day lag, while this news organization tracks them in real-time when they are reported by the county health department. CDPH also separates inmate populations, while this news organization does not, leading to higher rates represented here in Marin County than in CDPH data because of San Quentin State Prison.
Last updated: Wednesday, Sept. 16 with data from Tuesday
Case rate adjustment multiplier: < 2.4 tests/1,000 population = no adjustment; 2.41-2.99 = 0.88; 3-3.59=0.78; 3.6-4.19=0.71; 4.2-4.79=0.65; > 4.8 = 0.6
Alameda
Cases per 100,000 per day (past 7 days): 5.1
Tests per 1,000 per day (past 7 days): 2.5
Case rate adjustment multiplier: 0.88
Adjusted per-capita case rate: 4.5
Positivity rate: 2.0%
Contra Costa
Cases per 100,000 per day (past 7 days): 9.6
Tests per 1,000 per day (past 7 days): 2.5
Case rate adjustment multiplier: 0.6
Adjusted per-capita case rate: 8.4
Positivity rate: 3.9%
Marin
Cases per 100,000 per day (past 7 days): 6.0
Tests per 1,000 per day (past 7 days): 1.2
Case rate adjustment multiplier: n/a
Adjusted per-capita case rate: 6.0
Positivity rate: 5.1%
Napa
Cases per 100,000 per day (past 7 days): 6.4
Tests per 1,000 per day (past 7 days): 2.8
Case rate adjustment multiplier: 0.88
Adjusted per-capita case rate: 5.7
Positivity rate: 2.3%
San Francisco
Cases per 100,000 per day (past 7 days): 6.4
Tests per 1,000 per day (past 7 days): 4.0
Case rate adjustment multiplier: 0.71
Adjusted per-capita case rate: 4.5
Positivity rate: 1.6%
San Mateo
Cases per 100,000 per day (past 7 days): 9.0
Tests per 1,000 per day (past 7 days): 1.3
Case rate adjustment multiplier: n/a
Adjusted per-capita case rate: 9.0
Positivity rate: 6.6%
Santa Clara
Cases per 100,000 per day (past 7 days): 7.0
Tests per 1,000 per day (past 7 days): 3.8
Case rate adjustment multiplier: 0.78
Adjusted per-capita case rate: 5.0
Positivity rate: 2.3%
Solano
Cases per 100,000 per day (past 7 days): 7.2
Tests per 1,000 per day (past 7 days): 1.3
Case rate adjustment multiplier: n/a
Adjusted per-capita case rate: 7.2
Positivity rate: 5.6%
Sonoma
Cases per 100,000 per day (past 7 days): 8.4
Tests per 1,000 per day (past 7 days): 0.3
Case rate adjustment multiplier: n/a
Adjusted per-capita case rate: 8.4
Positivity rate: 15.0%*
* As of Monday
Official map, as of Sept. 15, with data as of Sept. 5
