LONG ISLAND (WABC) -- There are concerns over a potential rise in COVID-19 cases as the CDC reports increased levels of the coronavirus detected in sewage systems across the United States.
Nearly 40% of wastewater sampling sites reported at least some increase over the past 15 days, more than twice what it was a month ago.
"We've been watching it closely, of course," White House Press Secretary Jen Psaki said. "We currently have about 35,000 cases in this country. We expect some fluctuation, especially at this relatively low level, and, certainly, that to increase."
Experts say wastewater data cannot estimate the number of cases in a community, but monitoring it can serve as an early warning sign of increased transmission -- often detecting increasing infection days before positive case counts.
In Nassau County on Long Island, levels of COVID are recently on the rise again at Cedar Creek Wastewater Treatment Plant in Wantagh and at the Bay Park Water Treatment Plant in East Rockaway.
Even if the answers are in the wastewater, it's still hard for scientists to pinpoint precisely what they mean. Another COVID surge? Or a smaller COVID uptick with few medical consequences?
Dr. David Larsen from Syracuse University is testing wastewater around New York state.
"What it means is there's an increase in virus," he said. "Whether that means a surge in hospitalizations depends on the immunity levels in the population."
Experts also suggest the U.S. could follow Europe in seeing a major increase in cases of the omicron sub-variant known as BA.2, or "stealth omicron."
In the UK, BA.2 now accounts for more than 50% of cases. In the U.S., that number is only about 10%.
But with BA.2 spreading faster than omicron, that percentage is likely to rise.
"We're probably about three to four weeks behind the UK," former FDA Commissioner Dr. Scott Gottlieb said. "So while the UK is seeing a bump up of infections right now, we'll get further into our spring before we start to see it happen here."
The warnings come just days after Congress stripped $15 billion dollars in COVID funding from a spending bill.
The White House says, as a result, testing capacity could drop significantly in the coming weeks and supplies of COVID-related drugs could run low.
In China, the BA.2 variant is already behind the worst COVID outbreak in two years, with 51 million people now in lockdown.
Manufacturing in a major tech hub has shut down, prompting fears of more global supply-chain delays.
"China has a population that is very vulnerable to this new variant, and they haven't employed vaccines that are effective against this particular variant," former FDA Commissioner Dr. Scott Gottlieb said.
White House officials say the U.S. is at less risk than China because of the mRNA vaccines, which China did not use.
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