DOH uses wastewater monitoring to track virus
The first report analyzing wastewater from the state Department of Health confirms COVID-19 cases have dropped statewide since June, with the omicron subvariant BA.5 remaining the dominant strain.
However, the report said there has been an increase in the presence of the novel coronavirus, known as SARS CoV-2, found in Hawaii County wastewater.
“We are very carefully tracking what’s going on in the Big Island,” said State Laboratories Division Administrator Edward Desmond. “It’s too early, I think, to say what the significance of that is.”
The increase in SARS CoV-2 found in Hawaii County wastewater could indicate a not-yet-reported increase in COVID cases, a discrepancy between the types of wastewater samples being analyzed, or might be a more accurate reflection of the current case counts that often do under-reported due to at-home testing.
“Not all increases in wastewater concentrations have reflected surges in cases nationwide,” said Maria Steadmon, a fellow with the Association of Public Health Laboratories. “It could be possibly due to different sampling methods, but I think as we get more data within the next coming weeks, we can better interpret this trend.”
Those infected with COVID-19 begin shedding the virus in feces two to three days before the onset of symptoms, allowing wastewater testing to detect both symptomatic and asymptomatic cases early.
“Using wastewater surveillance data paired with the monitoring of COVID-19 case counts, hospitalizations and fatalities allows for a more complete understanding of disease patterns,” the wastewater report states. “When trends are similar across these measures, confidence in the accuracy of those trends increases.”
The DOH assists in collecting samples from 15 wastewater treatment plants across the state, including three in Hawaii County.
The collection is part of the National Wastewater Surveillance System, or NWSS, a federally funded program launched by the U.S. Centers for Disease Control and Prevention in September 2020. The samples are analyzed by Biobot Analytics in Cambridge, Mass., at no cost to Hawaii, with results provided within a week.
“The good thing about this system is that it enables us to compare results that we get by our own testing methods with those from the contract laboratory,” Desmond said.
When it comes to variant detection, the new wastewater data matches the DOH’s latest variant report released Sept. 27.
“Genome sequencing shows BA.5 is the most common subvariant in Hawaii,” said Desmond, with the report adding that “in some cases, variants have been detected in wastewater prior to detection in clinical samples.”
Wastewater data lists BA.5, BA.4, and BA.2.12.1 as the most common variants found on the Big Island. According to the latest variant report, BA.5 accounts for roughly 92% of all COVID cases throughout the state, and 95% of cases in Hawaii County.
But there are some limitations with wastewater data, especially when it comes to quantifying the number of cases.
“It’s hard to, even with the wastewater concentrations, accurately predict how many COVID-19 cases there are,” said Steadmon, with the report noting wastewater surveillance has a limited ability to capture low levels of infection in a community.
In addition to SARS CoV-2, wastewater data can be used to monitor the community presence of other viruses like monkeypox.
“We likely will be acquiring a commercially available kit to detect the monkeypox virus in wastewater sometime in the near future,” said Desmond, adding another long-term goal includes looking for antimicrobial resistance markers, which can detect antibiotic resistance in bacteria. “For example, if a new antibiotic-resistant organism has been introduced into the state, we might be able to find it early by looking at wastewater.”
Results from wastewater testing began in May, and both Desmond and Steadmon are hopeful it will be another useful tool to monitor the spread of COVID-19.
“This is one way of tracking the amount of COVID we have in the state,” Desmond said. “I think we can expect that in the future, if we have a surge in cases, we should detect it in the wastewater.”
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