How far has coronavirus spread?
This test is a first step in trying to get back to normal life
LOS ANGELES – It has been one of the most glaring unanswered questions of the coronavirus crisis: How much has the virus spread? A new study in Los Angeles County might help provide some answers.
Starting Friday, county health officials will begin testing the blood of 1,000 randomly selected residents, including those with no symptoms, to see if they have or had COVID-19. Using emerging technology that tests for antibodies to a virus, the study has the potential to shed light on the true mortality rate of the coronavirus, the efficacy of social distancing efforts and when this unprecedented clampdown on daily life could end.
Health officials and researchers say the results of this effort, known as serological testing, could paint the most complete picture yet of the sweep of the pandemic in the nation’s most populous county.
“Is it 1% of our population? Is it 10% of our population? That’s the difference between 80,000 adults and 800,000 adults. We have no idea,” said Dr. Paul Simon, chief science officer of the Los Angeles County Department of Public Health.
With the study’s launch, the county joins the growing ranks of governments and researchers that are turning to antibody tests as a new frontier in the campaign against COVID-19.
Antibody testing has already begun in Santa Clara County, with researchers drawing more than 3,000 people’s blood over two days last week at three drive-up testing sites. The Centers for Disease Control and Prevention began last week testing the blood of people living in coronavirus hot spots. And Thursday,
German health officials announced plans to run Europe’s first large-scale antibody testing program.
So far most testing has been done with nasal swabs, meant to detect the presence of the virus. But the pool of those tested has skewed toward the very ill, as health officials have put the highest-risk patients at the front of the line.
With the new blood tests, scientists hope to trace antibodies, which the body develops to fend off the coronavirus and linger after it is gone.
The presence of those antibodies probably offers some protection against reinfection, although it is not yet known the extent to which people would be immune from the virus.
The research aims to fill in a number of blanks about COVID-19, including how deadly the disease truly is – a figure that is difficult to pin down without knowing how many people have the virus, said Neeraj Sood, a professor and vice dean for research at USC’S Price School of Public Policy, who worked with the county on the study.
At this point, the county reports a death rate of 2.8% of people with confirmed cases. By contrast, the average death rate of the seasonal flu is 0.1%
“If the mortality rate of COVID is 10 times that of the flu, then we should all be freaking out and we should be staying at home and making sure that we practice very strong physical distancing,” Sood said. “But if the true mortality rate of COVID is five times less than the flu, then we don’t need to be doing that. Then it is a less deadly disease.”
Using antibody testing over time could also illuminate the effects of the aggressive physical distancing measures in Los Angeles and across most of the country – a step that has brought nearly all economic activity to a halt. If the rate of infection continues to climb in the population even with these measures in place, it may prompt politicians to rethink their usefulness in the face of massive job losses.
Additionally, the tests could offer clues as to when at least 60% of the population has at one point been infected, achieving “herd immunity,” which would significantly thwart the spread of the virus.
Experts caution that serological testing is not a panacea. It is still unclear how much immunity a person has from the coronavirus when antibodies are present. And the surge of new tests coming to the market means there is a wide variance in accuracy and reliability.
This week, Oxford University researchers found that at-home blood tests used in the U.K. were faulty, after the British government had ordered more than 4 million of such tests for residents.
“There are a lot of unknowns,” said Kevin de Leon, a former state Senate leader and incoming L.A. city councilman who has helped with the L.A. study’s launch. “However, we have this opportunity to scientifically determine whether there are those among us who can reenter the workforce safely, and we’ve got to seize it.”
So far, it has been impossible to quantify how many people have had the virus, because of a shortage of nasal swab test kits. The dearth of information threatened to hamper hospitals’ ability to prepare for the virus last month, as the wave of cases began to swell.
“I felt that we were flying blind,” said Dr. Brad Spellberg, chief medical officer at Los Angeles County-usc Medical Center. “We had no idea what was going on in the community around us.”
In mid-march, he decided to perform nasal swab tests on roughly 130 patients who came to his center’s emergency room and urgent care with mild flu-like symptoms. It offered a glimpse into a population beyond the highest-risk, most severe cases that have been the main focus of testing so far. He found that 5.3% of the patients with milder symptoms tested positive for COVID-19, a result he called “alarming.”
“These were young, active people,” Spellberg said. “They were going to work. They were going to community events. They had no idea that they had coronavirus and they had the real potential to be spreading this.”