NEW YORK -- As coronavirus infections rise in some parts of the world, experts are watching for a potential covid-19 surge in the United States and wondering how long it would take to detect.
Despite disease monitoring improvements over the past 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 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 effort 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.
But scientists also acknowledge that the wide availability of vaccines and treatments has put the nation in a better place than when the pandemic began, and 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 is that 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 had increased globally for two weeks in a row, 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."
VIRUS TESTING
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 performed each day on average -- four to six times the number of polymerase chain reaction tests, which are considered to be more reliable.
"The case numbers are not as much a reflection of reality as they once were," Nuzzo said.
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 it 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, adding 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.
MONITORING SYSTEM
An evolving monitoring system is looking for signs of the coronavirus in sewage, which has the potential to 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 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 and King County, Wash.
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 that 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 that "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, then 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 would provide enduring authority "so we will not risk flying blind as health threats emerge."
BOOSTER DOSES
As authorities brace for a possible increase in covid-19 cases caused by the BA.2 subvariant, 65.4% of Americans are fully vaccinated and just 44% have received a booster shot. Federal health officials are now considering authorizing fourth shots for people 65 and older.
But the nation's booster campaign, which was initially plagued by conflicting guidance and disagreement among advisers and scientists, has faltered: People who were willing to roll up their sleeves for first and second doses are seemingly less inclined to go for a third.
"This is an unforgivable liability that we did not get people boosted at a much higher level," said Eric Topol, director of the Scripps Research Translational Institute in San Diego.
A growing body of research has borne out the need for booster shots.
In a recent interview, Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, called the data "strong and highly convincing about the benefit of the booster."
While he said "nothing surprises me anymore," he expressed disappointment that fewer than half of vaccinated people are boosted -- and he said the United States needs to do better.
"If boosting was an iffy situation, that it doesn't help, then you could see, 'Well, what's the difference?'" Fauci said. "But it is a difference, because if you look at the data with boosting, it absolutely brings up the protection to a very high level."
But a majority of the vaccinated public has not been convinced.
The CDC says in a frequently asked question to health care professionals that vaccinated people who have recovered from prior infections can receive a booster dose. But the guidance is difficult to find, and recommendations on the timing of the shot are unclear.
A CDC spokeswoman did not respond to a request for comment. Representatives from the White House and the Department of Health and Human Services did not respond to an email asking about the declining number of new vaccinations.
A spokeswoman for CVS Pharmacy, which has shots available at 9,000 locations in the United States, said in an email that its pharmacies "adjust our orders frequently to account for covid-19 case trends. The government has also transitioned to allocating vaccine to pharmacies every two weeks, rather than every week, as was done earlier in the pandemic, and their allotments have declined based on recent trends as well."
A spokeswoman for Walgreens, which has administered 60 million doses of vaccine, said in an email that the company remains "committed to providing access to these services."
AMERICANS' RELUCTANCE
Polling by the Kaiser Family Foundation shows that the group that refuses even a first vaccination has remained at 12% to 16% since December 2020, a remarkably consistent segment of the population, according to Liz Hamel, the organization's vice president and director for public opinion and survey research.
"The job gets harder and harder over time," she said. "We see nothing in terms of messages or mandates that will move that 12[%] to 16%."
Among people who were vaccinated but not boosted, 35% told Kaiser pollsters in February that they would get a booster as soon as possible. But 24% said they would do so only if required, 23% said they definitely would not, and 16% said they would wait and see.
Overall, one of the most commonly named reasons for skipping the extra shot was the belief it isn't needed, according to a Kaiser survey from January. That explanation was given by 13% of non-boosted adults.
Another 12% said they were not eligible for a booster. Others had doubts about the effectiveness of boosters -- 9% cited the fact that vaccinated people were still getting sick.
According to the organization's February vaccine monitor, the booster rate was 68% among adults 65 and older but 34% among those 18 to 29 years old.
The failure to persuade the vaccinated to get boosted is "the most pitiful aspect of what we've done in the vaccine campaign," Topol said, adding that "these are not anti-vaxxers."
With fourth shots already on the horizon for some, he said the failure raised concerns about whether Americans would be willing to roll up their sleeves if needed again in the future.
"How can we do justice to the fourth shot when we have totally botched the third?" he asked.
Information for this article was contributed by Mike Stobbe, Lauran Neergaard and Laura Ungar of The Associated Press and by Brittany Shammas, Dan Keating, Salvador Rizzo, Lenny Bernstein, Akilah Johnson and Emily Guskin of The Washington Post.