By MIKE STOBBE

NEW YORK (AP) — As coronavirus infections rise in some parts of the world, experts are watching for a potential new COVID-19 surge in the U.S. — and wondering how long it will take to detect.

Despite disease monitoring improvements over the last two years, they say, some recent developments don’t bode well:

—As more people take rapid COVID-19 tests at home, fewer people are getting the gold-standard tests that the government relies on for case counts.

—The Centers for Disease Control and Prevention will soon use fewer labs to look for new variants.

—Health officials are increasingly focusing on hospital admissions, which rise only after a surge has arrived.

—A wastewater surveillance program remains a patchwork that cannot yet be counted on for the data needed to understand coming surges.

—White House officials say the government is running out of funds for vaccines, treatments and testing.

“We’re not in a great situation,” said Jennifer Nuzzo, a Brown University pandemic researcher.

Scientists acknowledge that the wide availability of vaccines and treatments puts the nation in a better place than when the pandemic began, and that monitoring has come a long way.

For example, scientists this week touted a 6-month-old program that tests international travelers flying into four U.S. airports. Genetic testing of a sample on Dec. 14 turned up a coronavirus variant — the descendant of omicron known as BA.2 — seven days earlier than any other reported detection in the U.S.

More good news: U.S. cases, hospitalizations and deaths have been falling for weeks.

But it’s different elsewhere. The World Health Organization this week reported that the number of new coronavirus cases increased two weeks in a row globally, likely because COVID-19 prevention measures have been halted in numerous countries and because BA.2 spreads more easily.

Some public health experts aren’t certain what that means for the U.S.

BA.2 accounts for a growing share of U.S. cases, the CDC said — more than one-third nationally and more than half in the Northeast. Small increases in overall case rates have been noted in New York, and in hospital admissions in New England.

Some of the northern U.S. states with the highest rates of BA.2, however, have some of the lowest case rates, noted Katriona Shea of Penn State University.

Dr. James Musser, an infectious disease specialist at Houston Methodist, called the national case data on BA.2 “murky.” He added: “What we really need is as much real-time data as possible … to inform decisions.”

Here’s what COVID-19 trackers are looking at and what worries scientists about them.

TEST RESULTS

Tallies of test results have been at the core of understanding coronavirus spread from the start, but they have always been flawed.

Initially, only sick people got tested, meaning case counts missed people who had no symptoms or were unable to get swabbed.

Home test kits became widely available last year, and demand took off when the omicron wave hit. But many people who take home tests don’t report results to anyone. Nor do health agencies attempt to gather them.

Mara Aspinall is managing director of an Arizona-based consulting company that tracks COVID-19 testing trends. She estimates that in January and February, about 8 million to 9 million rapid home tests were being done each day on average — four to six times the number of PCR tests.

Nuzzo said: “The case numbers are not as much a reflection of reality as they once were.”

HUNTING FOR VARIANTS

In early 2021, the U.S. was far behind other countries in using genetic tests to look for worrisome virus mutations.

A year ago, the agency signed deals with 10 large labs to do that genomic sequencing. The CDC will be reducing that program to three labs over the next two months.

The weekly volume of sequences performed through the contracts was much higher during the omicron wave in December and January, when more people were getting tested, and already has fallen to about 35,000. By late spring, it will be down to 10,000, although CDC officials say the contracts allow the volume to increase to more than 20,000 if necessary.

The agency also says turnaround time and quality standards have been improved in the new contracts, and that it does not expect the change will hurt its ability to find new variants.

Outside experts expressed concern.

“It’s really quite a substantial reduction in our baseline surveillance and intelligence system for tracking what’s out there,” said Bronwyn MacInnis, director of pathogen genomic surveillance at the Broad Institute of MIT and Harvard.

SEWAGE SURVEILLANCE

An evolving monitoring system is looking for signs of coronavirus in sewage, which could potentially capture brewing infections.

Researchers have linked wastewater samples to the number of positive COVID-19 tests a week later, suggesting health officials could get an early glimpse at infection trends.

Some health departments also have used sewage to look for variants. New York City, for example, detected signals of the omicron variant in a sample taken on Nov. 21 — about 10 days before the first case was reported in the U.S.

But experts note the system doesn’t cover the entire country. It also doesn’t distinguish who is infected.

“It’s a really important and promising strategy, no doubt. But the ultimate value is still probably yet to be understood,” said Dr. Jeff Duchin, the health officer for Seattle/King County, Washington.

HOSPITAL DATA

Last month, the CDC outlined a new set of measures for deciding whether to lift mask-wearing rules, focusing less on positive test results and more on hospitals.

Hospital admissions are a lagging indicator, given that a week or more can pass between infection and hospitalization. But a number of researchers believe the change is appropriate. They say hospital data is more reliable and more easily interpreted than case counts.

The lag also is not as long as one might think. Some studies have suggested many people wait to get tested. And when they finally do, the results aren’t always immediate.

Spencer Fox, a University of Texas data scientist who is part of a group that uses hospital and cellphone data to forecast COVID-19 for Austin, said “hospital admissions were the better signal” for a surge than test results.

There are concerns, however, about future hospital data.

If the federal government lifts its public health emergency declaration, officials will lose the ability to compel hospitals to report COVID-19 data, a group of former CDC directors recently wrote. They urged Congress to pass a law that will provide enduring authorities “so we will not risk flying blind as health threats emerge.”

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AP reporters Lauran Neergaard in Washington and Laura Ungar in Louisville, Kentucky, contributed.

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The Associated Press Health & Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education. The AP is solely responsible for all content.

By CHRIS MEGERIAN, LORNE COOK and AAMER MADHANI

BRUSSELS (AP) — Ukrainian President Volodymyr Zelenskyy called for “military assistance without limitations” as he addressed an emergency NATO summit on Thursday, the first of three urgent meetings U.S. President Joe Biden and world leaders are holding in response to the Russian invasion.

Zelenskyy pleaded for anti-air and anti-ship weapons, asking “is it possible to survive in such a war without this?”

“It feels like we’re in a gray area, between the West and Russia, defending our common values,” Zelenskyy said in his video address to the summit. “This is the scariest thing during a war — not to have clear answers to requests for help!”

A Biden administration official, who requested anonymity to discuss the closed summit, said Zelenskyy did not repeat his demand for a no-fly zone, a demand NATO already has rejected. Western officials fear such a step would lead to direct conflict between NATO and Russia, which Biden described as a potential World War III.

However, in brief opening remarks as the NATO summit began, Secretary-General Jens Stoltenberg said the alliance must boost its defenses and “respond to a new security reality in Europe.”

“We gather at a critical time for our security,” he told the leaders seated at a large round table. “We are united in condemning the Kremlin’s unprovoked aggression and in our support for Ukraine’s sovereignty and territorial integrity.”

Stoltenberg said the alliance is “determined to continue to impose costs on Russia to bring about the end of this brutal war.”

Over the course of Thursday, the European diplomatic capital is hosting the NATO summit, a gathering of the Group of Seven industrialized nations and a summit of the European Union. Biden will attend all three meetings and hold a news conference afterward.

The schedule left Brussels interlaced with multiple police checkpoints and road closures to help motorcades crisscross the city as the leaders go from one meeting to the next.

While the West has been largely unified in confronting Russia after it invaded Ukraine, there’s wide acknowledgement that unity will be tested as the costs of war chip at the global economy.

The bolstering of forces along NATO’s eastern flank, almost certainly for at least the next five to 10 years if Russia is to be effectively dissuaded, will also put pressure on national budgets.

“We need to do more, and therefore we need to invest more. There is a new sense of urgency and I expect that the leaders will agree to accelerate the investments in defense,” Stoltenberg said before the summit.

Biden’s national security adviser, Jake Sullivan, said the U.S. wants to hear “that the resolve and unity that we’ve seen for the past month will endure for as long as it takes.”

The energy crisis exacerbated by the war will be a particularly hot topic at the European Council summit, where leaders from Spain, Portugal, Italy and Greece are hoping for an urgent, coordinated bloc-wide response. EU officials have said they will seek U.S. help on a plan to top up natural gas storage facilities for next winter, and they also want the bloc to jointly purchase gas.

German Chancellor Olaf Scholz has dismissed calls to boycott Russian energy supplies, saying it would cause significant damage to his country’s economy. Scholz is facing pressure from environmental activists to quickly wean Germany off Russian energy, but he said the process will have to be gradual.

“To do so from one day to the next would mean plunging our country and all of Europe into recession,” Scholz said Wednesday.

Poland and other eastern flank NATO countries will also be looking for clarity on how the United States and fellow European nations can assist in dealing with their growing concerns about Russian aggression as well as a spiraling refugee crisis. More than 3.5 million refugees have fled Ukraine in recent weeks, including more than 2 million to Poland.

Biden is scheduled to visit Poland on Friday, where both issues are expected to be at the center of talks with President Andrzej Duda. Another significant moment could come shortly before Biden returns to Washington on Saturday. The White House said he plans to “deliver remarks on the united efforts of the free world to support the people of Ukraine, hold Russia accountable for its brutal war, and defend a future that is rooted in democratic principles.”

Sullivan said Biden and fellow leaders would aim to “set out a longer-term game plan” for what forces and capabilities are going to be required for the alliance’s eastern flank countries.

Four new NATO battlegroups, which usually number between 1,000-1,500 troops, are being set up in Hungary, Slovakia, Romania and Bulgaria.

Ukrainian President Volodymyr Zelenskyy, who is expected to address the NATO summit by video, said late Wednesday that he wants the alliance to “declare that it will fully assist Ukraine to win this war” by supplying any weapons necessary.

All the while, national security officials from Washington to Warsaw are increasingly worried that Putin might deploy chemical, biological or even nuclear weaponry. Sullivan said the allies would consult on how to respond to “potential contingencies” of that sort.

Biden said this week that the possibility of Russia deploying chemical weapons was a “real threat.”

Stoltenberg declined Thursday to discuss whether such a strike is a red line that would draw the alliance into war with Russia. “I will not speculate beyond the fact that NATO is always ready to defend, to protect and to react to any type of attack on a NATO allied country,” he said.

Kremlin spokesman Dmitry Peskov in a CNN interview this week said that Russia could consider using its nuclear weapons if it felt there was “an existential threat for our country.”

Ursula von der Leyen, head of the European Union’s executive arm, said before Biden’s visit that she wants to discuss the possibility of securing extra deliveries of liquefied natural gas from the United States for the 27-nation bloc “for the next two winters.”

The EU imports 90% of the natural gas used to generate electricity, heat homes and supply industry, with Russia supplying almost 40% of EU gas and a quarter of its oil. The bloc is looking at ways to reduce its dependence on Russian gas by diversifying suppliers.

Sullivan said the United States was looking for ways to “surge” LNG supplies to Europe to help.

Biden, for his part, was expected to detail plans for new sanctions against Russia and humanitarian assistance for the region.

One new sanctions option that Biden is weighing is to target members of the Russian State Duma, the lower house of parliament, according to a U.S. official who spoke on the condition of anonymity to discuss private deliberations. The new sanctions would be rolled out in coordination with Western allies.

Biden arrived in Brussels with Americans increasingly accepting of the need for the U.S. to help stop Putin, according to a poll from The Associated Press-NORC Center for Public Affairs Research.

But even as concern among Americans has swelled and and support for a major U.S. role in the conflict strengthened in the last month, Biden’s negative approval rating has not budged, the AP-NORC poll found. Few are very confident that he can handle a crisis, and a majority thinks he lacks toughness in dealing with Russia.

Biden promised voters that he had the experience to navigate a complicated international emergency like the one unfolding in Europe and his trip will be the latest test of that proposition as he tries to maintain unity among Western allies and brace for potentially even bigger challenges.

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Madhani reported from Washington. Associated Press writers Matthew Lee, Hannah Fingerhut and Darlene Superville in Washington and Samuel Petrequin in Brussels contributed to this report.