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Antibody testing suggests COVID-19 infections in L.A. County far more widespread

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2020-04-22 09:45:51Xinhua Editor : Gu Liping ECNS App Download
Special: Battle Against Novel Coronavirus

An early antibody testing conducted in Los Angeles County has suggested that the number of COVID-19 infections in the county greatly exceeds that of confirmed cases.

The county's infections from the virus are far more widespread while the fatality rate is much lower than previously thought, according to preliminary results from a collaborative scientific study by University of Southern California (USC) and Los Angeles County Department of Public Health earlier this week.

The results are from the first round of an ongoing study by USC researchers and local health officials. They will be conducting antibody testing over time on a series of representative samples of adults to determine the scope and spread of the pandemic across the county.

Based on results of the first round of testing, which was not peer-reviewed by other scientists, the researchers estimate that approximately 4.1 percent of the county's adult population has antibody to the virus.

Taking into account the statistical margin of error, the results indicate that 2.8 percent to 5.6 percent of the county's adult population has antibody to the virus, which translates to approximately 221,000 to 442,000 adults in the county who have had the infection.

The number is 28 to 55 times higher than the 7,994 confirmed cases of COVID-19 in the county at the time when the study began in early April.

As of Tuesday, the county reported 13,816 COVID-19 cases, including 617 deaths.

According to Neeraj Sood, vice dean for research at USC Sol Price School of Public Policy, the pilot test is helpful for the authority to know the true extent of COVID-19 infections as test availability is limited in the county.

The estimates can also be helpful for the local government to draw a plan for reopening business, Sood said.

Sood told Los Angeles Times in an earlier interview that, if the mortality rate of COVID-19 is 10 times that of the flu, people should all be staying at home and keep physical distancing, but if the true mortality rate is only five times less than the flu, the government could abandon its stay-at-home order.

California Governor Gavin Newsom also predicted early this month that antibody blood tests are "critical in terms of our capacity to make a determination about community spread and about immunity."

However, the World Health Organization (WHO) warned last Friday in a statement that antibody tests are basically useless when it comes to proving immunity, as the test can only show if antibodies are present in a person's blood but it is still unclear whether having antibody of COVID-19 imparts an universal immunity to be reinfected.

"These antibody tests will be able to measure that level of serology presence, that level of antibodies, but that does not mean that somebody with antibodies is immune," said Dr. Maria Van Kerkhove, head of the WHO's emerging diseases unit.

Mike Ryan, executive director of the WHO's emergencies program, also said nobody is sure that someone with antibodies is fully protected against having the disease or being exposed again.

The antibody test is helpful for identifying past infection, but a polymerase chain reaction (PCR) test is required to diagnose current infection.

Barbara Ferrer, director of Los Angeles County Department of Public Health, said in a press release that these findings underscored the importance of expanded PCR testing to diagnose those with infection so they can be isolated and quarantined while also maintaining the broad social distancing interventions.

"These results indicate that many persons may have been unknowingly infected and at risk of transmitting the virus to others," Ferrer said.

"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 Paul Simon, chief science officer at the county's public health department and co-author of the study. Enditem

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