Ochsner releases results of COVID-19 prevalence study done in multiple parishes

Updated: Aug. 20, 2020 at 4:34 PM CDT
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(WAFB) - About 60 percent of Baton Rouge residents who’ve had the coronavirus have been asymptomatic, a new study from the Ochsner hospital system shows.

Scientists estimate about 50,000 people had contracted the virus prior to August 1, roughly ten percent of the four-parish capital region that researchers studied. This means the region is not close to achieving herd immunity, where a significant portion of the population is immune to the virus because so many of them have already contracted it.

“There’s many people in our community who are susceptible to this virus and can catch it,” the study’s chief investigator, Dr. Leo Seoane, said. “If we didn’t do the things we’re doing right now, like wearing a mask and social distancing, (Baton Rouge) would be a powder keg and we would have thousands more infections.”

Ochsner researchers administered nasal swabs and antibody tests to more than 2,000 people, forming a sample of the Baton Rouge region. More people applied to participate in the research, but Ochsner was selective to account for demographic patterns.

During the testing period from July 15 to August 1, Ochsner estimates roughly 10,000 people had active Coronavirus infections but did not demonstrate symptoms.

“It’s here. It’s in our community. It’s going to be in our community for a while,” Ochsner chief medical officer Dr. Robert Hart said. “We have to respect and understand that, to keep that minimized for all the people around, the masks and social distancing is important.”

The study also confirmed other research that indicated white people are less likely to test COVID-positive than other races. By late July, 11.8 percent of the LatinX population had been infected, 11 percent of the Black population had been infected, and 4.2 percent of the white population had been infected.

“It started in African-American and white communities in Baton Rouge, but as of the last two weeks in July it is very active in the Hispanic communities of Baton Rouge,” Seoane said. “That tells you, as a health official, where we need to be spending resources.”

The study was conducted in partnership with the Baton Rouge Area Foundation (BRAF) and funded by the Louisiana COVID-19 Health Equity Task Force and The Humana Foundation, with support from The BlueCross BlueShield of Louisiana Foundation and Healthy Blue.

The study was led by Ochsner Principal Investigator Dr. Amy Feehan, in conjunction with Pennington Biomedical. In the study, data was analyzed to determine how widespread the virus is and which groups of people have been most impacted. More than 2,100 volunteers received free COVID-19 testing and antibody testing as part of the study.


  • 6.6% of Greater Baton Rouge residents (18+) have been infected with COVID-19
  • 3% tested positive for SARS-CoV-2 (COVID-19) but not antibodies, indicating that they are likely infectious. Projected to the larger population, we estimate more than 16,000 residents had an active infection at the time of testing.
  • More than 60% of those with an active infection had no symptoms at the time of the test (projected 10,000 residents)
  • 3.6% tested positive for antibodies, meaning they were recovering from the disease or had completely recovered. Projected to the larger population, we estimate 19,843 residents with antibodies.
  • The state-reported cases for this region (17,093, or 3.1%, as of Aug. 2) are in addition to this study as people with previous positive tests were not allowed to participate. Together, this region shows a 9.7% prevalence (6.6% + 3.1%) as of Aug. 2.
  • Active COVID-19 infections were most prominent in West Baton Rouge (5.3%) and Livingston (4.2%) parishes
  • Active infection rates were lower in East Baton Rouge (2.8%) and Ascension (1.9%) parishes
  • Black residents had the highest rate of past infection (positive antibodies), while Hispanic residents had higher rates of active infection
  • Antibodies were found in 7.5% of Black residents, 1.8% of White residents, and 1.6% of Hispanic residents
  • Active COVID-19 infections were found in 10.1% of Hispanic residents, 3.5% of Black residents, and 2.4% of White residents
  • Anosmia (loss of smell and taste) was associated with 8.5 times higher odds of testing positive
  • Comorbidities did not influence whether someone caught the virus - they influence the outcome. In fact, people with no comorbidities had higher odds of testing positive.
  • Residents with public-facing jobs (9%) had a much greater prevalence of positive tests than residents with office jobs (3%)
  • Those who reported working from home at least part of the time (3.7%) showed a much lower prevalence than those going in to work as usual (8.2%)


  • Given the high number of contagious people with no signs or symptoms, it’s extremely important to follow guidelines for mask wearing, social distancing, and hand-washing
  • You can’t be sure that you don’t have the virus just because you’re feeling well
  • If you experience loss of smell and taste, seek out a test or self-quarantine for 14 days to protect those around you
  • Participation with contact tracing and testing when appropriate is key to curbing the spread
  • Virus spread of less than 10% indicates we are not close to herd immunity, which would occur with an exposure rate of approximately 70 to 80%

“The data from this study is very telling,” said Eric McMillen, CEO of Ochsner Baton Rouge. “The results are factual evidence we can use to help educate our community about the spread of this virus and encourage our residents to continue wearing masks, social distancing, and following hand-washing guidelines.”

“It’s important to note that this study represents a specific moment in time,” stated Dr. Feehan. “Active infections continue to spread in our communities. We’re working to compare and contrast the data from the New Orleans study with our results from the Baton Rouge study.”

Ochsner says a followup report from Dr. Feehan is expected in the coming weeks and that more than 5,000 adults across New Orleans and Baton Rouge were tested for these studies.

Since May, Ochsner says it has completed more than 60,000 COVID-19 tests across the state. For more information about Ochsner testing location, click here.

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