Benicia COVID cases have risen to the CDC’s most dangerous “High Transmission level” since August 11 – well over the CDC’s “Substantial Transmission level.”

By Roger Straw, August 27, 2021  [UPDATED – note new information about the requirement of 30 days below substantial transmission level.]

Benicia’s new mask mandate refers to the CDC transmission levels as its standard for reviewing whether to continue the mask mandate.

The mandate will remain in place for 6 weeks, after which Council will review the order (on October 5).  The order will “remain in effect until the City is not in a substantial or high transmission of COVID 19 as defined by the CDC for a thirty-day period.” (From Resolution 21-88, adopted August 24)

The CDC’s formula for calculating level of transmission looks complicated, but it’s actually rather simple.  First, here is the CDC’s complicated presentation.  I’ll simplify after that….

TABLE. CDC core indicators of and thresholds for community transmission levels of SARS-CoV-2

Indicator	Transmission level
	Low	Moderate	Substantial	High
New cases per 100,000 persons in the past 7 days*	0–9.99	10.00–49.99	50.00–99.99	≥100.00
Percentage of positive nucleic acid amplification tests in the past 7 days†	<5.00	5.00–7.99	8.00–9.99	≥10.00

* Number of new cases in the county (or other administrative level) in the past 7 days divided by the population in the county (or other administrative level) multiplied by 100,000.
^† Number of positive tests in the county (or other administrative level) during the past 7 days divided by the total number of tests performed in the county (or other administrative level) during the past 7 days. https://www.cdc.gov/coronavirus/2019-ncov/lab/resources/calculating-percent-positivity.html

In the Benicia City Council discussions, only new cases per 100,000 was mentioned as a factor for review (unless I missed something).  Councilmember Tom Campbell did the math on the spot, and indicated that Benicia’s number would be 13 cases (later amended to 14) over the last 7 days.

Simply put, >>based on our population, when the County reports 14 or more new Benicia cases over the last 7 days, the CDC classifies us as having a level of “substantial transmission.”  If we see 28 cases over the last 7 days we are in an area of “high transmission.”  The mask mandate will continue until we have been below 14 new cases per week for at least 30 days.

The bad news… Here is a chart showing Benicia’s 7-day case levels per 100K over the past several weeks.  Clearly, we have been in Substantial or High since mid-July.

Solano County COVID-19 Dashboard – ARCHIVE
https://doitgis.maps.arcgis.com/apps/MapSeries/index.html?appid=055f81e9fe154da5860257e3f2489d67
Date	Total Confirmed Cases, Solano County	Δ	Total Confirmed Cases, Benicia	Δ	Cases previous 7 days per 100K  (CDC Substantial: Benicia 14+)
Wednesday, June 16, 2021	33,651	15	1,010	3	8
Thursday, June 17, 2021	33,673	22	1,012	2	9
Friday, June 18, 2021	33,707	34	1,015	3	12
Monday, June 21, 2021	33,762	55	1,017	2	11
Wednesday, June 23, 2021	33,797	35	1,021	4	11
Friday, June 25, 2021	33,846	49	1,025	4	10
Monday, June 28, 2021	33,898	52	1,029	4	12
Wednesday, June 30, 2021	33,973	75	1,029	0	8
Friday, July 2, 2021	34,044	71	1,030	1	5
Tuesday, July 6, 2021	34,149	105	1,038	8	9
Friday, July 9, 2021	34240	91	1,040	2	11
Monday, July 12, 2021	34377	137	1,045	5	15
Wednesday, July 14, 2021	34461	84	1,048	3	10
Friday, July 16, 2021	34630	169	1,056	8	16
Monday, July 19, 2021	34761	131	1,062	6	17
Wednesday, July 21, 2021	34885	124	1,070	8	22
Friday, July 23, 2021	35193	308	1,084	14	28
Monday, July 26, 2021	35482	289	1,092	8	30
Wednesday, July 28, 2021	35703	221	1,102	10	32
Friday, July 30, 2021	36004	301	1,110	8	26
Monday, August 2, 2021	36249	245	1,115	5	23
Wednesday, August 4, 2021	36525	276	1,125	10	23
Friday, August 6, 2021	36848	323	1,132	7	22
Monday, August 9, 2021	37056	208	1,141	9	26
Wednesday, August 11, 2021	37350	294	1,153	12	28
Friday, August 13, 2021	37664	314	1,167	14	35
Monday, August 16, 2021	37914	250	1,177	10	36
Wednesday, August 18, 2021	38294	380	1,187	10	34
Friday, August 20, 2021	38764	470	1,205	18	38
Monday, August 23, 2021	39002	238	1,216	11	39
Wednesday, August 25, 2021	39329	327	1,224	8	37

More CDC Resources:

• Guidance for Implementing COVID-19 Prevention Strategies in the Context of Varying Community Transmission Levels and Vaccination Coverage, July 30, 2021
• Calculating SARS-CoV-2 Laboratory Test Percent Positivity: CDC Methods and Considerations for Comparisons and Interpretation Updated May 24, 2021
• Guidance for Implementing COVID-19 Prevention Strategies in the Context of Varying Community Transmission Levels and Vaccination Coverage, July 30, 2021 (Scroll down to “Level of SARS-CoV-2 Community Transmission”
• CDC COVID Data Tracker (County View)