Wastewater data show San Diego COVID surge
Copies of the virus detected by research coalition nearly double in one week.
SAN DIEGO — Wastewater numbers show that San Diego County is experiencing a massive increase in coronavirus transmission driven by the BA.5 Omicron subvariant.
Testing detected 15.5 million coronavirus copies per liter of wastewater sampled Wednesday at the Point Loma treatment plant, according to the San Diego Epidemiology and Research for COVID Health Coalition, a group of labs led by UC San Diego and Scripps Research. That compares with 8 million copies per liter detected in the same sampling location one week earlier.
The trend visible in wastewater is starkly different from the one depicted by testing data released Thursday by San Diego County Public Health Services. Comparing the same Wednesday-to-Wednesday period, positive test results reported to the department fell 8.3%, from 2,191 to 2,007.
“We have every expectation that cases are eventually going to start rising the same way,” said Dr. Cameron Kaiser, deputy public health director for San Diego County.
Everyone is advised to do all they can to help slow the spread, he added. Though there is not a statewide mandate on masks, the use of one, especially in situations where many people are gathering, is strongly advised.
“We want everyone to step up; we want folks to get their shots and consider the events that they have to do and the events that they don’t,” Kaiser said. “We want the general public to get that good-quality, well-fitting mask out and put it on.
“The preponderance of the evidence shows that masks work, and we need to break the cycle of transmission.”
Wastewater is thought to be a better indicator of the true amount of virus circulating in a community than reported case counts, because the virus is shed into sewers even by those who are infected but have no symptoms that would cause them to get tested. Additionally, many who take at-home tests don’t share their results with local health departments, leading to undercounts.
The first Omicron wave, which began in December 2021, peaked Jan. 9 at 47.6 million coronavirus copies per liter of wastewater.
The situation is much different today. There’s no mask mandate in place (though some counties could soon impose them), and large community events are being scheduled to a much greater extent than this past winter.
Many are starting to again liken the coronavirus to the flu, suggesting that an overall drop in mortality from COVID-19 due to vaccination and better treatment options have removed the pandemic’s most severe threat.
But Kaiser disputed that notion, saying that while mortality rates are much lower than they were in 2020 and 2021, they are still greater than would be expected with the flu.
“BA.5 is certainly capable of killing,” Kaiser said. “We’ve had at least 33 San Diegans die of COVID in June, which is when BA.5 started to become more dominant.”
Dr. David “Davey” Smith, chief of infectious diseases at UC San Diego, said the current level of community activity suggests that viral transmission will continue to increase — a reality that should cause individuals to reassess their risk of infection and reinfection. It is clear that infection over the winter in the first Omicron wave is no guarantee of protection against BA.5.
“Even if you’ve been vaccinated, infected, boosted — all of those — doesn’t mean you are immune to the current variant,” Smith said.
The consequence of coronavirus reinfection is being studied, but Smith said there are indications that it could increase the chances of severe health consequences.
“You should try to dodge COVID as many times as you can, because it looks like getting repeated infections is probably not good for your health,” Smith said.
Does that mean canceling events?
The translational research virologist said he prefers a “harm reduction” strategy that emphasizes outdoor events, masking indoors and in heavy crowds and keeping plenty of social distance when possible.
“I’m not a cancel person; I’m a ‘Let’s take some precautions’ person,” Smith said.
Precautions are most important, he added, when interacting with people who are vulnerable. The elderly and those with underlying health problems such as diabetes or compromised immune systems are at increased risk of ending up in a hospital if they get sick with COVID-19.
“If you’re getting ready to go visit grandma who has a lot of issues, and you’re coming from a big event, it may not be the best time to have that exposure,” Smith said. “Test before you go visit grandma. You might be feeling well, but you could be asymptomatic. That’s the danger because, if you have it, you’re going to give it to grandma when you go visit, even if you don’t feel it.”
Confirmed and suspected COVID-related hospital admissions have continued to climb at nonmilitary hospitals in San Diego County, reaching 479 Wednesday, 69 more than one week ago.