How health departments determine if a positive COVID-19 case is the delta variant

Virus Outbreak Florida
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Posted at 3:23 PM, Aug 06, 2021
and last updated 2021-08-06 15:23:52-04

CLEVELAND — The Delta variant is now the dominant strain of COVID-19 in Ohio. In May, less than 1% of lab sequenced cases were identified as the highly contagious strain known as the Delta variant. The most recent data from the Ohio Department of Health between July 4 and July 17 shows that 86.4% of lab sequenced cases were the Delta variant.

“Delta spreads like wildfire and seeks out anyone who is unvaccinated. But there is good news as two things remain very clear: First, the vaccines are the key to containing this fire and ultimately putting it out,” said Ohio Department of Health Chief Medical Officer Bruce Vanderhoff, M.D. “Secondly, vaccination is without any doubt your best bet, regardless of your age, for avoiding getting really sick with COVID-19 and to avoid lasting complications like Long Covid.”

So how does the state know the majority of confirmed COVID-19 cases in the state are in fact the delta variant?

It comes down to genomic testing.

Summit County Public Health made sense of the confusion regarding how the presence of the delta variant is determined in the community by using a pregnancy test as an example.

When a person suspects they may be pregnant, they go to the local pharmacy and get a rapid pregnancy test. This test looks for specific markers in the urine provided to say “pregnant” or “not pregnant.”

If the result is “pregnant”, CONGRATULATIONS!!! Is the baby an XY (commonly referred to as a boy) or an XX (commonly referred to as a girl)?? Well, you need additional testing to find that out.

The same approach is done when there is a positive COVID-19 test. When a person suspects they have COVID-19, they go to a local testing site such as a pharmacy, to get a test. The test looks for specific markers in the sampled cells—coming back with either a “positive” or “negative” result.

If the test administered was a PCR test and it was positive, Summit County Public Health said it may be randomly selected to be sent to a specialist lab, like one at the Centers for Disease Control and Prevention, the Ohio Department of Health or a private lab, to get genetic testing to find out of it’s the delta strain.

While a PCR test only reports a “positive” or “negative” result, the material on the swab contains virus particles that can be tested to determine the variant that is present.

RELATED: 'We are at a new stage in this pandemic': DeWine encourages Ohioans -- again -- to get vaccinated

Health departments testing a particular positive sample may use genomic sequencing to identify levels of different variants in a community, which typically isn’t shared with individuals.

"Once the Delta variant is identified at these labs, statistical analyses can be applied to determine the rate of it in a community," Summit County Public Health said.

The CDC’s national SARS-CoV-2 genomic surveillance program identifies and tracks COVID-19 variants circulating in the United States. Genomic sequencing allows scientists to identify SARS-CoV-2 and monitor how it changes over time into new variants.

If you’re diagnosed in the U.S. with COVID-19, the odds that it's the delta variant are likely. The CDC estimates that delta accounts for more than 82% of cases in the United States.

The CDC uses the Nowcast model that projects more recent proportions of circulating variants. View an image from the CDC Nowcast model dashboard below, or click here to view the interactive data dashboard showing the variants across the U.S.

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CDC Nowcast Model Data Dashboard showing the prevalence of variants in the Midwestern United States.

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