Many virus outbreaks go unnoticed. Is It Possible to Track the Pandemic in a More Effective Way?

 Many virus outbreaks go unnoticed. Is It Possible to Track the Pandemic in a More Effective Way.

When the highly transmissible Omicron variant of the coronavirus arrived in the United States last fall, it pushed new case numbers to previously unseen peaks.

Even then, the record wave of recorded infections was a significant undercount of reality.

In New York City, for example, officials logged more than 538,000 new cases between January and mid-March, representing roughly 6 percent of the city’s population. But a recent survey of New York adults suggests that there could have been more than 1.3 million additional cases that were either never detected or never reported — and that 27 percent of the city’s adults may have been infected during those months.

The official tally of coronavirus infections in the United States has always been an underestimate. But as Americans increasingly turn to at-home tests, states shutter mass testing sites and institutions cut back on surveillance testing, case counts are becoming an increasingly unreliable measure of the virus’s true toll, scientists say.

“It seems like the blind spots are getting worse with time,” said Denis Nash, an epidemiologist at the CUNY Graduate School of Public Health & Health Policy who led the New York City analysis, which is preliminary and has not yet been published.

That could leave officials increasingly in the dark about the spread of the highly contagious new subvariant of Omicron known as BA.2, he said, adding, “We are going to be more likely to be surprised.” On Wednesday, New York officials announced that two new Omicron subvariants, both descended from BA.2, have been circulating in the state for weeks and are spreading even faster than the original version of BA.2.

The official case count can still pick up major trends, and it has begun to tick up again as BA.2 spreads. But undercounts are likely to be a bigger problem in the weeks ahead, experts said, and mass testing sites and widespread surveillance testing may never return.

“That’s the reality we find ourselves in,” said Kristian Andersen, a virologist at the Scripps Research Institute in San Diego. “We don’t really have eyes on the pandemic like we used to.”

To track BA.2, as well as future variants, officials will need to pull whatever insights they can from an array of existing indicators, including hospitalization rates and wastewater data. But truly keeping tabs on the virus will require more creative thinking and investment, scientists said.

For now, some scientists said, people can gauge their risk by deploying a lower-tech tool: paying attention to whether people they know are catching the virus.

“If you’re hearing your friends and your co-workers get sick, that means your risk is up and that means you probably need to be testing and masking,” said Samuel Scarpino, the vice president of pathogen surveillance at the Rockefeller Foundation’s Pandemic Prevention Institute.

Tracking the virus has been a challenge since the earliest days of the pandemic, when testing was severely constrained. Even when testing improved, many people did not have the time or resources to seek it out — or had asymptomatic infections that never made themselves known.

By the time Omicron hit, a new challenge was presenting itself: At-home tests had finally become more widely available, and many Americans relied on them to get through the winter holidays. Many of those results were never reported.

“We haven’t done the groundwork to systematically capture those cases on a national level,” said Katelyn Jetelina, an epidemiologist at the University of Texas Health Science Center at Houston.

Some jurisdictions and test manufacturers have developed digital tools that allow people to report their test results. But one recent study suggests that it may take work to get people to use them. Residents of six communities across the country were invited to use an app or an online platform to order free tests, log their results and then, if they chose, send that data to their state health departments.

Nearly 180,000 households used the digital assistant to order the tests, but just 8 percent of them logged any results on the platform, researchers found, and only three-quarters of those reports were sent on to health officials.

General Covid fatigue, as well as the protection that vaccination provides against severe symptoms, may also prompt fewer people to seek testing, experts said. And citing a lack of funds, the federal government recently announced that it would stop reimbursing health care providers for the cost of testing uninsured patients, prompting some providers to stop offering those tests for free. That could make uninsured Americans especially reluctant to test, Dr. Jetelina said.

“The poorest neighborhoods will have even more depressed case numbers than high-income neighborhoods,” she noted.