Few COVID cases are tested for delta variant. Here’s why NC officials trust the numbers.

Over 75% of COVID-19 tests from North Carolina in recent weeks are the delta variant, but the testing sample makes up less than 10% of all tests, a N.C. Department of Health and Human Services official said.

State epidemiologist Zack Moore said the current sequencing is from the week ending July 10.

Nationwide, over 83% of tests sequenced are the delta variant, according to the Centers for Disease Control and Prevention.

The sequenced virus that is tested for the delta variant, which is more transmissible and possibly more deadly, makes up about only 6% to 10% of all COVID-19 tests statewide.

Moore said DHHS currently sequences tests from the state laboratory, the CDC, commercial labs such as Labcorp, and from University of North Carolina Health.

He said DHHS is working with the N.C. Policy Collaboratory, a state organization that publishes research from the UNC school system, to get more sequencing data from COVID-19 tests in the state.

“We’re working towards this broader network that will give us access to sequencing data from a wider range of places,” Moore said.

But even though the amount of sequenced tests is low, it has increased from a few months ago, Moore said.

And it still indicates that the delta variant is spreading in North Carolina.

“It’s not rocket science,” Moore said. “The delta variant is replacing all other variants globally, nationally, and in North Carolina. That’s what we’re seeing with our data here, so we’re very confident that this is a true reflection of what’s going on this variant.”

Health officials have said that the delta variant is causing the rise in cases in recent weeks.

In the last week, North Carolina has reported 7,298 new cases of COVID-19, up from 4,571 from the week prior. That’s an increase of nearly 60%.

Health officials say the available vaccines still protect against infection from the delta variant, especially warding off severe cases that require hospitalization.

In recent weeks, 99% of new cases and 98% of hospitalizations are among people who have not been vaccinated, according to DHHS.

As of Wednesday, 60% of adults in North Carolina have received at least one dose, and 56% are fully vaccinated.

How sequencing works

Moore said there is a delay of a few weeks in delta variant reporting because of how the process works.

He said a lab first has to collect its positive tests. Then a select few test results are sent away for sequencing, where the genome structure of the virus is examined.

After the viruses are examined, which can take a few days, the results need to be interpreted and reported.

“It’s not a rapid process,” Moore said.

It’s not as simple as testing for the coronavirus, he said, where it can be determined in a matter of days if someones is carrying SARS-CoV-2, the virus that causes COVID-19.

“The tests that people get that tell you if it’s positive or negative don’t give you the type of information that you need to know what variant it might be. That requires additional, much more complicated [testing], looking at the entire genome sequence of the virus,” Moore said.

He said DHHS is working to shorten the reporting time.

This delay is seen nationwide as well. The latest data from the CDC only goes up until July 3 on the state level and July 17 nationwide.

And the nationwide number is a projection two weeks out based on current trends in available data.

Is it a representative sample?

The few tests that are sent in for examination currently, Moore said, are mostly tests where people have recently traveled internationally or have tested positive after being vaccinated.

Moore said once the larger infrastructure with N.C. Collaboratory is established, they will be able to gather a more representative sample.

“When we have this network up and running, we’ll have much better ability to look at urban versus rural specimens, from people who are hospitalized compared to those who were not, look across different age groups and demographic groups,” Moore said. “That’s why we’re trying to increase our sequencing infrastructure, so we’ll get a better [representation] across a number of different ways.”

He said this more detailed data should be publicly available within a month.

Regardless of how prevalent the delta variant is, Moore said the prevention measures are the same — masking in certain settings, quarantining after a positive test and getting vaccinated.

“Those types of prevention measures are not different, depending on which particular variant you might have,” Moore said. “The things that we’ve been recommending and encouraging people to do are the same.”