Health
Hundreds of thousands of Los Angeles County residents may have been infected with the coronavirus by early April, far outpacing the number of officially confirmed cases, according to a report released Monday.
The initial results from the first large-scale study tracking the spread of the coronavirus in the county found that 2.8% to 5.6% of adults have antibodies to the virus in their blood, an indication of past exposure.
That translates to roughly 221,000 to 442,000 adults who have recovered from an infection, according to the researchers conducting the study, even though the county had reported fewer than 8,000 cases at that time.
“We haven’t known the true extent of COVID-19 infections in our community because we have only tested people with symptoms, and the availability of tests has been limited,” study leader Neeraj Sood, a professor at USC‘s Price School for Public Policy, said in a statement. “The estimates also suggest that we might have to recalibrate disease prediction models and rethink public health strategies.”
The findings suggest the coronavirus is far more widespread than originally known, and that its fatality rate is much lower. But Sood cautioned against solely focusing on how lethal the disease is.
“We are very early in the epidemic, and many more people in L.A. County could potentially be impacted,” Sood said in a news briefing. “And as those number of infections arise, so will the number of deaths, the number of hospitalizations, and the number of ICU admissions.”
The early results from L.A. County come three days after Stanford researchers reported that the coronavirus appears to have circulated much more widely in Santa Clara County than previously thought.
The Stanford team estimated that 2.5% to 4.2% of Santa Clara County residents had antibodies to the coronavirus in their blood by early April.
Though the county had reported roughly 1,000 cases in early April, the Stanford researchers estimate the actual number was 48,000 to 81,000, or 50 to 85 times greater.
The Santa Clara study recruited around 3,300 participants from social media, which has raised some concerns that the results may not be representative of the county as a whole. The researchers made adjustments to their data to account for that problem.
The study was composed differently in Los Angeles; 863 adults were selected through a market research firm to represent the makeup of the county. The county and USC researchers intend to repeat the study every two to three weeks for several months, in order to track the trajectory of the virus’ spread.
Both counties used rapid antibody tests supplied from Premier Biotech, a Minneapolis-based company. The test has not yet been approved by the FDA, although the federal government does allow for such tests to be used for public health surveillance.
As antibody testing, also known as serological tests, has risen in prominence, so too have concerns about accuracy over the results.
The L.A. County Public Health Department cautioned healthcare providers last week against interpreting results from such tests “until there is additional data on their best use because of concerns of both false negative and false positive results.”
Nevertheless, antibody tests have increasingly become a focal point in the response to coronavirus because they can potentially show the true extent of the virus’ reach and therefore can shed light on how close the population is to achieving herd immunity, in which enough people have some degree of immunity to the virus that it becomes difficult for infections to spread.
Such tests can also provide a more accurate picture of how lethal the virus is. Right now, the mortality rate is based on the number of confirmed infections, but the higher the number of infections, the lower the fatality rate.
“Though the results indicate a lower risk of death among those with infection than was previously thought, the number of COVID-related deaths each day continues to mount, highlighting the need for continued vigorous prevention and control efforts,” said Dr. Paul Simon, chief science officer at the L.A. County Department of Public Health and co-lead on the study.
The researchers, whose work has not been peer reviewed, did not offer an estimate of the actual mortality rate.
Preliminary data from Los Angeles found that men were more likely to be infected than women, and blacks were more likely than other racial and ethnic groups to test positive for the virus. But Sood warned against reading too much into the findings, noting it is too early to know if there is a real statistical difference between the various groups.
It is unlikely the initial findings will cause county officials to immediately change their response to the virus. Barbara Ferrer, the county’s top health official, said that the high rate of infection only underscored the need to continue with physical distancing.
“We need to assume that at any point in time, we could be infected and that all of the other people we come in contact with could also be infected,” Ferrer said Monday. “And that means keeping our distance, using our cloth face coverings when we’re in close contact with people and staying home if you’re sick, so that you don’t expose anybody else to any of your germs.”
Ferrer also took pains to note that much is still unknown about whether the presence of antibodies to this virus means a person is immune.
“I do want to issue a reminder that being positive for COVID-19 antibodies does not mean that a person is immune, or that a person is not able to be reinfected,” Ferrer said. “More research is really needed to understand what protections people have who may have already been infected with COVID-19.”
Health Coronavirus more prevalent in L.A. County, tests suggest - Los Angeles Times
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