The C.D.C. no longer recommends universal case investigation and contact tracing.

The C.D.C. announced that 100,000 contact tracers should be created almost two years ago by the Director of the Centers for Disease Control and Prevention. This week, the C.D.C. stated that it no longer recommends universal contact tracing and case investigation. Instead, it encourages the health departments to focus their efforts on high-risk areas.

This is the turning point, as the national outlook continues its rapid improvement with new cases, hospitalizations, and deaths continuing to fall, even though the path out from the pandemic remains difficult. It also reflects that approximately half of the U.S. states have eliminated contact-tracing programs.

Last week, Britain stopped contact tracing. Denmark and Finland were among the other countries that have reduced their use of contact tracer. New York City announced Tuesday it would be ending its main contact-tracing program by April end and instead will treat the coronavirus, a manageable viral infection.

“This is a big change,” Crystal Watson, a senior scholar at the Johns Hopkins Center for Health Security, said in an interview on Tuesday. “It does reflect what’s already happening in states and localities, particularly with Omicron. It was impossible for contact tracing to keep up with this. Many of the cases are not being reported, so there’s no way of knowing the incidence.”

Contact tracing in America was originally designed to reach people who had spent more than fifteen minutes within six feet from an infected person. Then, ask them to quarantine their home for two week if they do not test positive. The goal was to reduce transmission. Americans who had been infected monitored their symptoms and kept them informed. It is used to identify clusters and outbreaks that may require intervention from the health department.

The pandemic began, and states and cities struggled with the detection of the virus’ prevalence due to sporadic and sometimes rationed diagnostic testing as well as long delays in receiving results.

Now, the C.D.C. The C.D.C. is urging health departments to concentrate on high-risk settings like long-term care facilities and jails. Many Americans with compromised immune systems feel that they are being left behind by the removal of all restrictions and precautions.

“The updated guidance is in response to changes in the nature of the pandemic and the increasing availability of new tools to prevent transmission and mitigate illness,” Kristen Nordlund, a spokeswoman for the C.D.C., said Tuesday.

She explained that the dominant variants with short incubation periods, rapid transmissibility and high levels infection- or vaccine-induced immunity made it possible to make the change.

Dr. Watson, who was also the lead author of a 2020 study recommending that the country have 100,000 contacts tracers, expressed concern that her new guidance might lead the country to dismantle the infrastructure that was in place to support as high as 70,000 contact tracers during the winter surge 2020.

“We anticipate that there will be a need for contact tracing,” she said, “so some of the investments made in rebuilding the public health work force should be used more broadly so we can call on them in the next emergency.”

Hemi Twarson, executive director of National Academy for State Health Policy, said that more states have statewide contact trace programs.

“I actually think that the federal government move is consistent with what states are doing,” she said in an interview on Tuesday. “They’re already concentrating contact tracing on high-risk settings.”

Ms. Tewarson stated contact tracing couldn’t keep up with Omicron surge. She also said that it wasn’t as effective if people were testing at home and weren’t reporting results.

“As a longer term plan, this is going to be more sustainable,” she said. “We’re at a different stage of the pandemic.”