Doctors explain 3 factors behind surge in San Francisco COVID cases

ByLuz Pena KGO logo

Wednesday, August 11, 2021

Doctors explain 3 factors behind surge in SF COVID cases

San Francisco surpassed the nation's 7-day rolling average case rate, even though 78% of the population is fully vaccinated. Here's what doctors say contributed to the surge:

SAN FRANCISCO (KGO) -- San Francisco surpassed the nation's 7-day rolling average case rate, even though 78% of the population is fully vaccinated.

Medical experts are attributing this sudden increase in San Francisco to three factors; the Delta variant, the unvaccinated population and the reopening of California on June 15.

Close to two months after California reopened and San Francisco became the first city to reach a milestone of 80% of the eligible population vaccinated with one dose, now San Francisco is surpassing the nation's 7-day rolling average case rate.

Luz Pena: "What do you think is driving this increase?"

Dr. Warner Greene: "Delta, Delta, Delta. This variant is sweeping through the country including the Bay Area"

Based on the latest CDC data from Aug. 8, San Francisco's 7-day rolling average was 43.3 daily cases per 100,000 people. The US 7-day rolling average was 33.26 daily cases per 100,000 people.

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Dr. Greene, Director and Senior Investigator for the Gladstone Institutes of Virology and Immunology says the numbers go hand in hand with the reopening.

"People are interacting as a society continues to work. Even if we are masking indoors as we are doing now. There is still a chance," said Dr. Greene,

Luz Pena: "How can that be in San Francisco where over 70% of the population is fully vaccinated?"

Dr. Greene: "Most of the infections that we are seeing in the Bay Area are occurring in unvaccinated individuals and we need to encourage all of those unvaccinated individuals to get vaccinated. I also suspect that we are seeing more breakthrough infections than we previously appreciated, but those are not progressing to serious disease."

The silver lining is that San Francisco hospitals are not overwhelmed.

Dr. Christopher Colwell, Chief of Emergency Medicine at Zuckerberg San Francisco General Hospital says the majority of those hospitalized with COVID continue to be unvaccinated and the ones with breakthrough cases are particularly in the elderly and immune compromised population.

"I don't see indication that we are going to be overwhelmed. We are bracing for a significant 4th surge, but I strongly suspect that we in San Francisco are going to be ready for it and particularly if we can react and continue to trim down in the positivity rates," said Dr. Colwell.

Over email San Francisco's Department of Public Health responded:

"San Francisco's response to the COVID-19 pandemic has resulted in extremely high vaccination rates, with 78% of the eligible population fully vaccinated. As we continue to reopen our economy and welcomed visitors to the City this summer and fall, San Francisco's coordinated response continues as we mitigate the harm the pandemic can do to our City. While increases in cases were expected when we reopened our economy in alignment with the state on June 15, the Delta variant has definitely has brought new challenges. We are doing everything possible to get more of our eligible population vaccinated, our best tool to keep cases stable and protect people from COVID-19, and its variants.

As we have seen since the beginning of the pandemic, new infections are not distributed evenly throughout all neighborhoods and communities in San Francisco, which is why our focus and work for vaccine equity and access continues in partnership with the communities that are most impacted.

We encourage everyone who is eligible and have not yet done so, to get vaccinated as soon as possible to help keep themselves and their community safe."

SFDPH also said one potential factor in comparing case rates is whether San Francisco is testing at a higher rate.

"We are testing for sure but it's not like this is an artifact of more testing. This is the virus, this is Delta doing what it does," said Dr. Greene.

Dr. Greene says what's helping San Francisco now is that the majority of the population has embraced the vaccines, but the numbers could continue to go up if that 30% or so of the population is not fully vaccinated.

Another concern is that as more people are infected with COVID the virus will continue to mutate increasing the possibility of a new variant to emerge and evade the vaccines.

VACCINE TRACKER: How California is doing, when you can get a coronavirus vaccine

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