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Coronavirus test tube samples

The Los Angeles County Department of Public Health conducts Polymerase Chain Reaction (PCR) test for COVID-19 on March 19, 2020.

The number of confirmed coronavirus cases in Los Angeles County topped 40,000 today, while results of the latest antibody testing showed a drop in the percentage of residents believed to have been infected at some point, an indication the virus' spread is slowing.

Health officials warned, however, that there could be an array of explanations for the drop in antibody-positive tests between the first survey in April and the second this month.

The latest survey found 2.1% of the 1,014 adults who were tested had antibodies to COVID-19 in their systems, indicating they had been infected at some point. That was down from about 4.1% in the first round of testing in April, which involved 863 test subjects

The testing is aimed at painting a broader picture of how widespread coronavirus infections are in the community. Projected across the county's 10 million residents, a 2.1% infection rate would equate to roughly 210,000 people -- far greater than the county's current number of confirmed cases, which is around 40,000.

The first round of serology testing in April found about 4.1% of residents had antibodies in their system, suggesting an infection number of about 400,000.

Neeraj Sood, a USC professor of public policy at the USC Price School for Public Policy and lead investigator on the antibody study, noted several changes in methodology between the two rounds of testing, most notably a greater outreach to Spanish- and Mandarin-speaking residents in the May survey, along with changes in testing sites that contributed to different demographics.

The two percentages also fall within a standard margin of error in the testing, officials said. Sood also noted that people who may have been infected early in the pandemic may have "waning" levels of antibodies in their system that were not detected by the testing.

Promising Testing Results

But he said there is reason to be optimistic over the latest testing results.

"What we find is that between the two waves there is no evidence of a big increase in incidence of COVID-19," Sood said. " ... This shows that we are controlling the new infections in our community. The results still say, if you pool the results across the two waves, ... about 3% tested positive, which means we are still far away from herd immunity, and we need to be conscious of that."

Barbara Ferrer, director of the county Department of Public Health, echoed that optimistic tone, while also acknowledging that methodology may have contributed to the drop in percentage of antibody-positive tests.

"Despite the limitations, the results suggest there was not much spread in the virus in the general community population during the time between these two surveys and I think this is likely because so many us did a great job staying at home, physically distancing and wearing our cloth face coverings."

She noted that the latest testing, like the first round, found that men are more likely to be infected with the virus, as are people in lower- income neighborhoods and people under age 55.

Additional rounds of serology testing are being planned, with officials saying they will be making efforts to include a broader array of the population, while also including people in nursing homes and children.

Ferrer today announced 57 more deaths due to the coronavirus in the county, although 13 of those deaths were actually reported late Tuesday by health officials in Long Beach and Pasadena. Long Beach and Pasadena both reported three additional deaths Wednesday afternoon. The new deaths increased the county's total to 1,976.

The county announced another 1,324 cases of COVID-19, while Long Beach and Pasadena combined to add 118 more, raising the county total to 40,975.

COVID-19 Economic Fallout

The county has been slowly reopening recreational amenities and retail businesses for curbside pickup only. The county's Economic Resiliency Task Force, which includes members of the Board of Supervisors and local business leaders, met on Tuesday and set a target date of July 4 for a full or staged reopening of most of the county's economy.

Supervisor Kathryn Barger said today that goal was set following a meeting that included some dire numbers presented by business leaders.

"It was sobering," she said. The restaurant industry reported that 80% of jobs have been lost while the entertainment industry indicated that 890,000 film and entertainment employees were out of a job.

"... Anyone listening to yesterday's meeting heard loud and clear that employees and businesses are suffering," Barger said. "I understand the urgency to reopen quickly, but we must do it safely and public health guidance has to (guide) what we do."


Public Health has issued the following guidance for people with mild illness during this time of increased spread:

Stay at home whenever possible and practice social distancing -- keep at least six-feet away from others when you leave your home.

 Wash your hands with soap and water as frequently as possible for at least 20 seconds. Use hand sanitizer when water is not available. 

 The general public should wear non-medical face coverings when interacting with others while obtaining essential supplies and services.  You should not purchase hospital-grade masks, which are in short supply and desperately needed in hospitals. People can use scarves or other fabric, suggesting that people go online for instructions on how to fashion a homemade mask.

 If you are mildly sick, stay home for at least seven days and until 72 hours after being fever and symptom free. Call your doctor if you are concerned and/or your symptoms worsen. Individuals who are elderly, have underlying health conditions or pregnant should consider contacting their providers earlier when they are sick.

Additional things you can do to protect yourself, your family and your community are on the Public Health website.

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