Despite protests and reopening, Bay Area COVID-19 data is stable for now

As other areas in the state and country see evidence of dramatically increased coronavirus transmission, key metrics in the San Francisco Bay Area remain mostly encouraging.

Despite the case increases, the numbers for hospitalizations and percentage of positive tests — a pair of metrics deemed the best way to measure spread by UCSF epidemiologist Dr. George Rutherford — are either declining or stable in most Bay Area counties.

“The easiest thing to look at is case counts, which is not a perfect metric since you have to factor in increased testing,” Rutherford told SFGATE earlier this month. “We’re finding more asymptomatic cases now, so it’s not exactly comparable to March and April, when most detected cases were symptomatic. Now in May and June, we’re catching more asymptomatic cases so it can be hard to interpret since we’re finding more infections.”

RELATED: Cheat sheet: How to decipher your county’s COVID-19 data

Marin County is the lone Bay Area county that has seen an increase in both hospitalizations and percentage of positive tests over the past two weeks, and even with a new seven-day average of 6.6 percent test positivity, the county remains under the 8.0 percent benchmark state officials have set as a goal for counties to remain under.

Even though the percent positivity of tests is ticking up slightly in some Bay Area counties, the increase is small when compared to what is happening elsewhere in the country. Specifically, the percent positivity of tests in Florida has increased from 2.0 percent to 16.1 percent in a matter of weeks, and in Arizona that figure has jumped up the low single-digits to 19 percent in the same time period.

Here’s a county-by-county look at hospitalization and percent positivity figures. All data comes from individual county websites and the state’s database for county-by-county hospitalizations.

San Francisco (3,249 confirmed cases)

Seven-day average for hospitalizations on June 8: 39 patients

Seven-day average for hospitalizations on June 22: 35.6 patients

Seven-day average for percent positive test rate on June 8: 1.6 percent

Seven-day average for percent positive test rate on June 21*: 2.0 percent

*San Francisco’s testing data only goes up to June 21

San Mateo (2,961 confirmed cases)

Seven-day average for hospitalizations on June 8: 55.1 patients

Seven-day average for hospitalizations on June 22: 23.3 patients

Seven-day average for percent positive test rate on June 8: 3.5 percent

Seven-day average for percent positive test rate on June 22: 4.4 percent

Alameda (5,140 confirmed cases)

Seven-day average for hospitalizations on June 8: 87.4 patients

Seven-day average for hospitalizations on June 22: 81.9 patients

Seven-day average for percent positive test rate on June 8: 3.9 percent 

Seven-day average for percent positive test rate on June 22: 3.5 percent

Contra Costa (2,454 confirmed cases)

Seven-day average for hospitalizations on June 8: 17 patients

Seven-day average for hospitalizations on June 22: 29 patients

Seven-day average for percent positive test rate on June 8: 4.7 percent

Seven-day average for percent positive test rate on June 22: 3.2 percent

Santa Clara (3,727 confirmed cases)

Seven-day average for hospitalizations on June 8: 65.6 patients

Seven-day average for hospitalizations on June 22: 56 patients

Seven-day average for percent positive test rate on June 8: 1.5 percent

Seven-day average for percent positive test rate on June 22: 2.0 percent

Marin (984 confirmed cases)

Seven-day average for hospitalizations on June 8: 1.7 patients

Seven-day average for hospitalizations on June 22: 6.1 patients

Seven-day average for percent positive test rate on June 8: 4.1 percent

Seven-day average for percent positive test rate on June 19*: 6.6 percent

*Marin County’s testing data only goes up to June 19.

Solano (1,020 confirmed cases)

Seven-day average for hospitalizations on June 8: 11.9 patients

Seven-day average for hospitalizations on June 22: 15.3 patients

NOTE: Solano does not report the daily percent positive test rate, only cumulative testing data.

Napa (245 confirmed cases)

Seven-day average for hospitalizations on June 8: 0.6 patients

Seven-day average for hospitalizations on June 22: 3.7 patients

NOTE: Napa does not report the daily percent positive test rate, only cumulative testing data.

Sonoma (956 confirmed cases)

Seven-day average for hospitalizations on June 8: 13.6 patients

Seven-day average for hospitalizations on June 22: 10.8 patients

NOTE: Sonoma does not report the daily percent positive test rate.

Rutherford told SFGATE in mid-June that it typically takes 7-10 days to gauge the impact of an event such as a protest or reopening phase in the case totals or percent positivity numbers. Because Bay Area counties reopened in-store retail, outdoor dining and other sectors in early June — the same time the protests started — we should expect to see a significant shift in percent positivity by now if these events were going to have a big impact on transmission.

In addition, most patients who end up needing to be hospitalized for COVID-19 reach that stage 7-10 days after symptoms surface so hospitalization rates lag slightly behind other metrics.

However, Rutherford, citing data from Minneapolis, stated there was no guarantee the protests or other outdoor activities would lead to an increase in virus transmission.

“Minnesota (is) falling steadily; there’s one slight uptick on June 1 but that may be because of weekend reporting lags,” he said a full two weeks after the protests over the death of George Floyd started in Minneapolis on May 25. “But it’s all trending down. If you look back seven to 10 days, you would expect to be seeing a significant jump by now.”

Because protesters were not keeping six feet of physical distance but many were wearing masks, Rutherford believes there’s one clear takeaway.

“Masks work,” he said. “Masks are the most important thing. I would say masks trump social distancing as far as a practical protection. And the open air, where the virus is not being held in by four walls, a roof and floor also helps … This is not great science and no one is going to win the Nobel Prize for it, but if you have a large upswing in activity, and then seven to 10 days after the event, not a lot of transmission went on, that’s not nothing.”

Eric Ting is an SFGATE digital reporter. Email: [email protected] | Twitter:@_ericting

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