Sentinel testing tracks asymptomatic COVID spread, Delta variant cases

RAPID CITY, S.D. — The State of South Dakota has utilized voluntary sentinel testing over the past year to track asymptomatic spread in our communities – including testing adults in class settings, long-term care centers, and correctional facilities.

It differs from traditional diagnostic testing in that it only tests individuals exhibiting no symptoms.

“And as you know, not everybody with COVID-19 will have symptoms,” says Dr. Tim Southern, laboratory director at the South Dakota Public Health Laboratory.

Traditional diagnostic testing is used to determine right then if a person showing symptoms has COVID or something else.

“Sentinel testing is very important because it allows us to determine if we have asymptomatic spread within the populations that we’re monitoring,” Dr. Southern says.

The South Dakota Department of Health and Public Health Lab also partner with the Minnesota Public Health Lab and the Centers for Disease Control and Prevention to sequence batches.

Dr. Southern adds, “One of the things that the data from sequencing tell us is that the delta variant is the predominant variant in South Dakota – in fact – one of the last sequencing runs – or batches of samples that we sequenced – 100% of them were a delta variant.”

Dr. Southern says that even without sequencing each individual sample – based on the numbers – the lab can determine that most South Dakotans being infected with coronavirus are being infected by that specific delta variant.