A well-designed study of blood samples from Orange County residents found that 12% of people have coronavirus antibodies, which means their immune system fights the virus at some point and the infection rate is higher than the official number of cases Seven times out.
The researchers found that this means that at least 371,000 people in Orange County have COVID-19.
The rate is highest among Latino residents and low-income adults, and the lowest among non-Latino white and black residents and residents with annual incomes of more than $100,000.
The results also showed that the virus is extremely contagious and more widespread than the case data indicates, and the mortality rate is much lower. Nevertheless, it is still higher than seasonal flu.
Tim Bruckner, research leader and associate professor of public health at the University of California, Irvine, said: “The most surprising among researchers is the high seropositivity rate for COVID.” “We doubt, If we focus on the entire community instead of just those who ask for testing, there will be more cases, but we don’t know how popular it is.”
Bruckner said most people who test positive have no symptoms. The focus may be on the so-called “super spreader” incident, but the virus does spread regularly, quietly and invisible.
Although more than 10% of Orange County residents tested in the summer have COVID-19 antibodies, there is still a long way to go compared to “group immunity” because when so many people have antibodies, this The virus will deplete the new host. Scientists say that approximately 60% to 70% of the population must be immune to eliminate infection.
“We are far from herd immunity,” Bruckner said. “Our views are very close, and the argument that we are about to turn danger into peace has not been confirmed by data.”
A city-sized case
Dr. Matt Zahn, medical director of the Infectious Disease Control Division of the County Health Care Bureau, was surprised that the number of people who caught the coronavirus in Orange County exceeded the number of people living in its largest city, Anaheim.
Zahn said at a press conference on Wednesday, October 28: “This number is both a very large and a very small number.”
He said that this is evidence supported by research that proves how easy the spread of COVID-19 is. At the same time, this shows that the virus still has a lot of room to spread.
For Bernadette Boden-Albala, the director of the Public Health Program at the University of California, Irvine, a social epidemiologist and research leader, this also illustrates the large differences (if any) in the way people exhibit various symptoms.
“Obviously, we have heard of the most serious cases, hospitalized cases, deaths, but we did not have all the asymptomatic and mild symptoms because people don’t think they are sick and are spreading diseases,” she said.
“This is very important data that can help us consider plans for the future.”
More evidence of health inequality
Although data from active infections have shown that low-income and Latino communities have been hit hard by infections, this study highlights this in a powerful way.
The prevalence of Latino residents is 17%, and that of low-income residents is 15%. The study said this may be due to relatively dense housing conditions and working in environments that do not allow physical distance.
This is consistent with a large number of swab tests conducted in low-income Latino communities in Anaheim and Santa Ana.
“In a city like Santa Ana, our positive rate is as high as 30%,” Boden Albala said.
Boden-Albara said that the Orange County Health Care Bureau worked with nonprofit organizations such as Hispanic Health Access to curb the unusually high return rate of positive test results in hot spots in the county. Such campaigns have brought more tests and resources to communities where many residents cannot work from home and have little access to medical services.
On October 6, public health officials installed the Coronavirus Parallax Tracking System in the state’s four-level pandemic surveillance system. The system looks at the state’s 58 counties’ case rates and test positive rates and other indicators, and determines when it can Reopen.
More common and less lethal
The case data (taken from busy patients at diagnostic test sites, clinics, and hospitals) concluded that the COVID death rate for elderly people 65 and older in Orange County is about 10%.
“That’s another part of the story, it’s very interesting,” Bruckner said. “Obviously, COVID is a killer, and I never want to say that. That is to say, as you count more cases of asymptomatic and mild symptoms, the fatality rate will decrease.
“The point is, based on your different methods of calculating COVID deaths, we overestimate the deaths in OC by 4 to 10 times.”
In short, the study estimates that 1 in every 1,000 infected people will die among people under 65, and about 10 in every 1,000 people who are over 65 will die.
“According to our estimates, this means that out of 100 adults over 65 have died of COVID,” Bruckner said. “It’s very serious. But it’s not 10%. It’s an estimate based on who is in the clinic.”
The study said that the widespread COVID in Orange County deserves continued public health measures: physical distancing, correct and consistent use of masks, ventilation and hand hygiene.
Moreover, in addition to contact tracing, county health authorities “may also wish to consider active surveillance for new infections.” This will involve approximately 800 to 1,000 tests in a representative sample of residents each week, as well as targeted components for high-risk groups or locations (such as nursing home residents, workers in high-density environments, and severely affected communities).
The study said: “Unlike clinical or hospital-based strategies, this surveillance will provide a biased estimate of the new SARS-CoV-2 infection rate.”
Finally, since the death rate estimates have been reduced several times, “the updated estimates should provide a reference for the broader US policy debate on the relative benefits and limitations of various SARS-CoV-2 mitigation strategies.”
How to do it
UCI researchers co-led the project with OC Health Care Agency, which provided funding, testing sites, and research and investigation methods.
Its design is more comprehensive and stricter than the previous version, and it includes more people than people tested in Los Angeles or Santa Clara County. The researchers came to the homes of people who were unable to drive across the site. They focused specifically on underserved communities and did not initially indicate that they would provide blood or serological tests to avoid pre-selecting people who might want it.
Since the beginning of the pandemic, fingers and blood drawn from 2,979 adults from July 10 to August 16 were later than similar studies conducted in Los Angeles and Santa Clara Counties in the spring. UCI researchers are planning to do more work on racial and ethnic differences, geographic hot spots, and track people who have tested positive over a period of time to understand how long the immunity can last.
Neeraj Sood, a professor of public policy in the School of Price Public Policy at the University of Southern California, and the lead researcher of a groundbreaking serological study conducted by the University of Southern California and the Los Angeles County Department of Public Health this summer, said this is a prominent problem.
Sood said: “The level of antibodies you have and the rate of decline may be related to the severity of your disease.” Sood also plans to study people who have tested positive in Los Angeles County over a period of time. “There is more and more evidence that the seroprevalence rate is declining over time. Therefore, even serological testing may underestimate the true prevalence-we may have only detected the infection in the past few months, not a pandemic Since the beginning.
UCI’s Bruckner said that one of the big gains from OC’s work is that many people know about COVID but don’t, which supports the view that this virus is a silent spreader. He said: “It is necessary to adopt a continuous public health strategy that concerns the entire population, not just those who think they are sick.”