COVID-19’s delta variant is quickly spreading in California. Here’s what you need to know.


For the first time since early January, COVID-19 cases and hospitalizations are on the upswing again, largely driven by the spread of the more contagious delta variant.

The Department of Public Health in seven Bay Area counties and a city issued an advisory Friday morning recommending – not required – that everyone, regardless of vaccination status, wear masks in indoor public places. Los Angeles County became the first California county restored an indoor mask warrant Thursday.

Here are answers to all your questions about the uptick, what drives it and what comes next.

How does the spread of COVID increase in California?

The cases are ticking back up, but are nowhere near the levels hitting near the end of the winter in February.

The statewide test positivity rate is 3.5%, compared to 1.7% in July and 0.9% when the state completely reopened June 15.


The positivity rate is the percentage of all coronavirus tests performed that are positive. “A higher positive percentage suggests higher transmission and that there is likely to be more people with coronavirus in the community who have not been tested yet,” Johns Hopkins University says.

State and local health officials said the vast majority of the new infections are occurring among those who are not vaccinated. In Los Angeles County specifically, health director Barbara Ferrer estimated at 99% in new cases, hospitalizations and deaths are among those vaccinated. While there are some breakthrough infections among those who are fully vaccinated, these infections remain rare and serious illness is even more rare.

Of the 10 California counties that report the highest rates of new cases each day, only one – Sonoma County – has a vaccination rate in excess of 50%.

What percentage of COVID cases in California are delta variants?


The delta variant, first identified in India and more contagious than the original COVID-19 strain but it does not appear to cause more serious illness, currently accounts for about 58% of COVID-19 cases in the United States, according to the latest data from the CDC, which analyzed cases up to 3 July.

CDC data indicate that in the region including California, Nevada and Arizona, the delta variant is 62% of the cases.

The California Department of Public Health monitors the spread of variants throughout California. The state has developed a variant tracking page that explains how, who and why to track tracking. At the bottom of the web page, the state also provides information about known variants and what proportion of variants have changed over time. Visit the state variant tracking site at www.cdph.ca.gov/Programs/CID/DCDC/Pages/COVID-19/COVID-Variants.aspx.

Which California and Bay Area count has tightened mask restrictions to combat the variant?

Alameda, Contra Costa, Marine, San Francisco, San Mateo, Santa Clara, Sonoma and the city of Berkeley published notices Friday morning recommending – not required – that everyone, regardless of the vaccination status, wear masks in public homes.

Marine County Health Director Dr. Matt Willis explained in a phone call that a mask recommendation helps prevent the spread because infected and asymptomatic vaccinators can pass the virus on to unvaccinated people who can develop serious illness.

“Tools are more common than initially thought for the delta variant,” Willis said. “Clinical trials did not test efficacy. They were testing how well this person was protected.”

Mayor London Breed hint at a press conference Thursday what new mask guidelines may come.

“We’re considering, basically, giving advice on suggested mask-wearing in certain cases,” Race you say Thursday at a press conference with reporters. “We demand that people who are not vaccinated, when they go indoors, that they wear masks and people who are vaccinated we don’t necessarily have a mask condition beyond that, but we are looking at a change in the policy , but not necessarily a warrant. “

Napa and Solano counties responded via email that they will continue to align with state guidelines and monitor cases and hospitalizations.

“Napa County will not be more restrictive than the state council,” Napa County spokeswoman Danielle Adams wrote. “Although Napa County has had more cases, hospital admissions are still low. We will continue to monitor cases with hospital admissions.”

Solano County said in an email “Solano Public Health will continue to monitor the situation and remove barriers to the vaccination by focusing on low-income neighborhoods and partnering with community organizations.” “Vaccinating as many people as possible, as soon as possible, is our best defense against COVID-19, the delta variant and the harm it can do to our communities.”

Outside the Bay Area, two counties, Yolo and Sacramento, are recommended that everyone – even those who are completely vaccinated – wears indoor masks. Those are only recommendations for now.

Los Angeles County has issued a new health order that reimposes an indoor mask warrant. It is unclear how long this term will last.

Will Governor Gavin Newsom restore the condition of the mask statewide?

The state Department of Public Health did not directly address the question of whether a state mandate will be restored, emphasizing rather that “vaccines remain the best protection against COVID-19, including the highly infectious delta variant.”

The department said in a statement, “Non-vaccinated Californians not only have a higher risk of getting COVID-19 than all those who are completely vaccinated, but they are also more likely to suffer from serious, hospitalized diseases. hospital and death. ” “As we continue to see the real and aggressive impact of the delta variant in rising case rates, we cannot stress enough how critical it is for those eligible to be vaccinated.”

In addition, the department said it “supports (their) capacity of local health jurisdictions to adopt stricter local public health councils that adapt to the situation in their communities, as some counties have done.”

Should I wear a mask even if my county doesn’t require it?

The answer to this question depends on who you talk to: SFGATE has contacted two experts at UCSF who have been closely working on the COVID-19 pandemic with different opinions.

Dr. Monica Gandhi, an infectious disease doctor at UCSF, said in an email to SFGATE that she does not think a new mask condition is necessary.

“I’m not because I’m very convinced that the approach by our top ID doctor (Dr. Fauci) to the country and the CDC is taking is sound,” Dr. Gandhi wrote in an email. “They are very clear that they do not intend to recommend masks for vaccination nationwide (White House task force brief July 8 21:33) but that we should focus on vaccination efforts and epidemic management and wave testing, treatment and vaccination for places in the country and high hospitalization rates among those who are not vaccinated. “

UCSF infectious disease expert Dr. Peter Chin-Hong, on the other hand, said via email that he thinks, and travelers coming to the Bay Area from other parts of the country with different levels of circulating virus and vaccination rates, set a indoor masks would not hurt, particularly as can be mounted locally.

Chin-Hong wrote: “The point is that we want to protect those who are not vaccinated as there is increased reports about those who are vaccinated getting infected.” “This is still a rare circumstance, and people who are vaccinated will rarely get sick after infection, but nevertheless a moving target. It would still be a bummer (school, missed work) even to get infected as someone who gets vaccinated the vaccine and anxiety induced so wearing that indoor mask is not a bad idea for a cheap and painless intervention. “

Where is the Variant Spread in the Bay Area?

We asked all nine Bay Area counters this question. Six answers:

Solano County spokesman Jose Caballero, wrote in an email: “Like the surrounding counties, Solano County has seen an increase in cases after July 4. Most cases are in smaller groups with the lowest vaccination rate. For more statistical information, check out County Solano COVID-19 and the Vaccine dashboard. https://doitgis.maps.arcgis.com/apps/MapSeries/index.html. “

Sonoma County spokesman Matt Brown wrote: “We have detected 68 cases of delta variants so far. This does not mean that no more in the county, just how many have been confirmed in genotypes in state laboratories, which is a process We have recently acquired new equipment to make genotypes in-house, so I suspect we will be able to identify more variant cases. “

Adams of Napa County said via email: “As of Tuesday 7/13 (when the Test Data page was updated but this number is still current), there were 11 known cases of the Delta variant in Napa County from a cumulative total of 10,143 It is not really possible to tell case rates with the Delta variant because not all laboratory samples are sequentially determined .. We also do not track or report ‘active’ versus ‘closed’ cases, so we do not there is a way to tell how many current cases are due to Delta, either. 7 out of 11 people who tested positive for the Delta variant were completely vaccinated at the time of the positive tests, which is about 64%. “

Contra Costa County’s email reads: “Our case rate (currently at 5.7 per 100k) has doubled over the past few weeks. Over the past two weeks, 76% of COVID-19 test samples are sequenced in our public health laboratory “Keep in mind, this is just a sample but it’s safe to say that we’ve seen deltas gradually grow.” The county also noted that it doesn’t have data on the number of people who tested positive for the variant and are was vaccinated.

Willis of Marine County said on the phone, “We’re seeing waves of cases. We’ve seen a quadruple of our cases rates in less than a month. We’ve been in less than a new case every day per 100,000. We currently at 4.5 cases per 100,000 residents. “

Willis added that one of three new cases is tool infection where an individual test is fully positive.

“We don’t see the corresponding wave of hospitalizations or deaths,” Willis said. “While we’re seeing an increase in the proportion of our cases that are tool breakthroughs, vaccine coverage is clear in preventing serious illness. That’s what interests us first.”

He added, “While the delta variant seems to be breaking through vaccines more than other variants, the vaccine protects against serious disease. The question may become: What should we measure? If these are asymptomatic people who are vaccinated being diagnosed with COVID-19 what are the public health implications of that? ”

The San Francisco Emergency Operations Center said it cannot provide an exact number of delta cases at the moment.

How bad is the spread of the delta variant in San Francisco?

In highly vaccinated San Francisco, where 76% of those 12 and over are fully vaccinated, daily cases can increase four times over the week ending July 7, for which there are complete data, the San Francisco Department of Public Health said. Cases ranged from a low of 9.9 cases daily on June 19 to 42 new cases daily on 7 July.

“Forward looking data up to July 12 indicate that new cases will increase to at least 73 cases / day, a seven-fold increase since June 19,” authorities said.

UCSF Dr. Bob Wachter has been following San Francisco COVID numbers throughout the pandemic, he says about Twitter on Thursday that SF numbers are still “fairly low” and “cause for caution, don’t panic.”

“But this kind of uptick in SF (the U.S. vaccination leader) shows that Delta is very real – where they w / lower vax rates may well get clobbered,” Wachter wrote. “Alas, it doesn’t seem like there are many persuasives left.”

The city did not indicate how many of those cases were in people who were not vaccinated, but Gandhi said in an email that 99% of those in the hospital with COVID-19 across the county are not vaccinated (including 19 in San Francisco).

Gandhi said: “The most important thing to know about deltas is that vaccines are sensitive.”

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