DHHS: Nebraska wastewater sampling indicates COVID-19 variants ahead of verified cases

Published: May. 11, 2022 at 7:34 PM CDT
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OMAHA, Neb. (WOWT) - Wastewater analysis data from communities across the state is helping experts in Nebraska get a clearer picture of the evolution of COVID-19 variants these last 14 months.

The Nebraska Department of Health and Human Services released a report Wednesday summarizing more than a year of wastewater sampling to determine COVID-19 levels across the state.

DHHS, the University of Nebraska-Lincoln, the UNMC College of Public Health, and wastewater utilities across the state have been working together to monitor COVID-19 levels in feces at wastewater plants in communities across Nebraska since March 2021. The hope is that by analyzing the patterns — determining detectability, prevalence, and transmissibility — the data can help identify trends that can help inform public health responses to become more proactive rather than reactive. The information could also help officials understand how the variants are affected — if at all — by current vaccination levels.

“Wastewater surveillance is an emerging public health tool,” the DHHS informational site states. “There is evidence that the quantity of SARS-CoV-2 in wastewater is correlated with infections in the wastewater sewershed area.”

While noting that researchers are still evaluating the value and effectiveness of the sampling as a public health aid, recommending the information be used as supplemental data alongside other sorts of trend monitoring, the study makes a case for wastewater sampling as an equalizer in COVID-19 data collection.

“Wastewater surveillance does not depend on people having access to healthcare, those seeking healthcare when sick, or availability of COVID-19 testing,” the site states.

Early warnings?

Sampling occurred at two wastewater plants in Douglas County, two in Lancaster, and at one in each of Platte, Madison, Hall, Adams, Buffalo, Lincoln, Scotts Bluff, and Dawes counties.

Comparing wastewater analysis against reported case data in each of the Douglas County plants during the peak of the omicron wave in early 2022 showed indicators were present in the wastewater about two weeks ahead of case reports. In Lancaster County, those peak indicator levels seemed about three weeks ahead of peak case reports.

In the Grand Island area, charts in the report show Hall County’s wastewater showed a small spike in late February into mid-March that never manifested in verified case numbers — a phenomenon that also seems to have happened at about the same time in Scotts Bluff County as well. Conversely, case rates in the Chadron area indicated a small spike in late February that didn’t seem to register as dramatically in the wastewater data.

Variant waves charted

DHHS arranged the data into charts showing the emergence, prevalence, and recession of known COVID-19 variants. The visuals make it easy to identify the speed of omicron and the staying power of delta.

The data shows the delta variant moving into Nebraska communities starting in early May 2021, and accounting for the majority of cases by mid-July that year. It remains as the dominant strain, accounting for almost every case, from the end of July 2021 until January 2022, when the omicron variant begins to take over. According to the data, omicron was first detected in early December 2021 and was the dominant variant by New Year’s, with BA.2 detected in late January.

The state’s chart shows delta’s staying power, with the variant taking about six weeks to go from detection-level to majority status, where it remained for five months. Comparatively, omicron took about a month to span the same levels, while BA.2 seem on track to follow a similar path in about two months.

It also shows indicators of variants that never took hold. For example: Gamma variant cases tripled from May 22, 2021, to June 5, 2021, and accounted for 6% more cases than delta in early June 2021 but was soon overshadowed by delta variant cases.

Preliminary data dated May 7 shows a small percentage of cases identified as BA.4 variant — at nearly the same levels as the initial appearances of previous COVID-19 variants.

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