The level of coronavirus found in two New Orleans wastewater sites rose nearly 700% over the last two weeks, according to data reported by the Centers for Disease Control and Prevention. While virus levels in Louisiana remain low, the recent data has infectious disease experts on alert after weeks of declining cases and loosening restrictions.
“We’re in a little bit of a fog right now, but certainly wastewater suggests SARS-CoV-2 is definitely here and it does seem to be – at best we can tell – increasing,” said Susan Hassig, an infectious disease epidemiologist at Tulane University.
The rise in wastewater levels comes amid other early signs of more infections. The state reported 604 cases over the last seven days compared to around 450 the week before, an increase of about 33%. More cases are likely going undetected with the use of at-home tests, which are not reported to public officials.
In addition, hospitalizations increased by 12 patients last Friday, dropped slightly over the weekend and then increased again on Monday and Tuesday, for a total of 63 patients in hospitals in Louisiana.
The rising levels of COVID nationwide and in Louisiana are driven in part by the BA.2 subvariant of omicron, estimated to be about 50% to 60% more infectious than the original omicron variant that fueled a surge this past winter. It makes up 84% of COVID cases in the southwest region and 43% of cases in Louisiana as of April 2.
It’s too early to tell if the uptick will continue, but health experts are closely watching other states that are seeing increases in cases and hospitalizations. The five states with the highest 7-day case increases are in the Northeast, according to the CDC. New hospital admissions are also beginning to creep up in that region. Officials in Philadelphia recently reinstated a mask mandate, citing sharply rising infections.
“Part of what we can do and probably should do is watch what happens in the Northeast, in terms of the timeline,” said Hassig. “They’ve been reasonable predictors, usually about 3 to 4 to 5 weeks ahead of us through most of these waves.”
Wastewater in New Orleans — which reflects virus particles shed in saliva, urine and feces — has shown higher levels of coronavirus since the CDC started tracking it in mid-February. The increase was reflected in samples taken at the end of March and has been steadily increasing through April 9, the most recent data available.
Although wastewater sampling has been used since the early days of the pandemic, it has emerged as an early warning system relied on by the federal government as part as a pathway to a more normal life in recent months. Samples from the Sewerage and Water Board’s two wastewater treatment sites on the east and west banks are collected daily and sent to the CDC. About 65% of the nearly 450 wastewater sites across the country have recorded an increase in COVID levels over the last two weeks. More collection sites from Louisiana are planned, according to officials from the Louisiana Department of Health.
Not every increase recorded by the CDC can be interpreted as a certain sign of an upcoming surge, said Aaron Bivins, co-founder of the COVID-19 Wastewater-based Epidemiology Collaborative and assistant professor with LSU’s Department of Civil and Environmental Engineering. The significance of a percentage increase depends on the baseline from the prior week, and Louisiana’s increases still remain below the threshold of a 1,000% increase that Bivins would consider alarming when virus levels are low.
Still, “my antennae are up,” said Bivins. “This change in trend is definitely concerning.”
A consistent increase in COVID wastewater levels over the next few weeks would be cause for risk management measures like mask-wearing and reconsidering whether to go out to eat, Bivins said. A collision of rising infections with Easter weekend, French Quarter Fest and Jazz Fest, along with less available testing as federal funding runs out, may lead to more transmission.
Residents infected during the omicron surge likely still have some protection, Hassig pointed out. But that diminishes after about three months, and nearly half of Louisiana remains unvaccinated.
“That is probably giving us a little bit of a buffer, but it’s going to start really disappearing quickly as we get into May,” Hassig said.
Staff writer Jeff Adelson contributed to this report.
Emily Woodruff covers public health for The Times-Picayune | The Advocate as a Report For America corps member.
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