As the Trump administration moves to dismantle international public health safeguards, pull funding from local health departments and legitimize health misinformation, some experts now fear that the country is setting the stage for a long-term measles resurgence.

If federal health officials do not change course, large multistate outbreaks like the one that has torn through West Texas, jumping to neighboring states and killing two people, may become the norm.

“We have really opened the door for this virus to come back,” said Dr. Thomas R. Frieden, a former director of the Centers for Disease Control and Prevention.

In order for an outbreak to occur in the United States, the virus must first be imported into the country, and it must reach a large, unvaccinated population.

Recent events have made both conditions seem increasingly likely, said Dr. William Moss, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health.

Efforts to control the spread of measles internationally have been disrupted by the Trump administration’s recent decision to withdraw from the World Health Organization, which runs a network of more than 700 laboratories that track measles cases in 164 countries.

The program — which helps to ensure prompt public health responses to emerging outbreaks — relies on the United States to fund its entire $8 million annual budget.

Administration officials also have signaled that they intend to end U.S. funding for Gavi, an organization that help purchase vaccines, including those for measles, mumps and rubella, in developing countries.

The funds for Gavi were not included on a list the State Department sent to Congress last week of programs it intends to continue to support. But the organization has yet to receive a formal grant termination letter, and its leadership is lobbying the administration to preserve the funding.

Both the W.H.O. withdrawal and the possible loss of Gavi’s funding are likely to cause a surge in measles cases overseas, increasing the likelihood that a U.S. traveler will bring the virus back into the country, said Dr. Walter Orenstein, a professor emeritus at Emory University and the former director of the National Immunization Program at the C.D.C.

“People don’t understand that supporting global immunization not only is good for their countries, but for our country,” he said.

This week’s layoffs at the C.D.C. included staff members who communicate with the public during infectious disease outbreaks and help craft campaigns to encourage vaccination.

Now communications will be centralized at the Department of Health and Human Services, under the control of health secretary Robert F. Kennedy Jr., a vaccine skeptic. The department did not respond to requests for comment.

Dr. Frieden, the former C.D.C. director, described the cuts as “a recipe for disaster.”

The national immunization rate for measles, which fell during the Covid-19 pandemic, has not rebounded to the 95 percent required to stem the spread of the virus in a community. That raises the odds that an imported case will land in a vulnerable population and ignite.

Roughly 93 percent of children in kindergarten had the M.M.R. shot in the 2023-24 school year. But vaccination rates are unevenly distributed; some communities have rates around 80 percent, offset by others where the figure is closer to 99 percent.

Now that H.H.S. has moved to cut billions of dollars to local health departments, they may struggle to quash outbreaks early on, allowing the virus to hop to other unvaccinated communities. (A judge temporarily blocked the funding cuts after a coalition of states sued the Trump administration.)

During infectious disease emergencies, it is local health departments that investigate the source of the pathogen and track down anyone who might have been exposed so they can be quarantined.

The contact-tracing process is time consuming and resource intensive, especially for a virus as contagious as measles.

“A fire is burning and we are at the same time shutting down all the fire departments,” said Jennifer Nuzzo, director of the Pandemic Center at the Brown University School of Public Health.

The current outbreak that began in West Texas shows no signs of slowing. There have been more than 480 cases in the area and 56 hospitalizations since late January. The outbreak has also spread to bordering states, sickening 54 people in New Mexico and 10 in Oklahoma.

Genetic sequencing has suggested that the outbreak is also linked to 24 measles cases discovered in southwest Kansas.

Measles was officially eliminated in the United State in 2000. But the speed at which the Texas outbreak has grown and the fact that it has already jumped to other, under-vaccinated communities makes it very likely that the United States will lose that status, Dr. Nuzzo said.

Measles is no longer considered eliminated if a chain of infections continues for more than twelve months. Public health officials in West Texas have predicted the outbreak will continue for a year.

A large measles outbreak that spread through parts of New York State for nearly 12 months nearly cost the country its elimination status in 2019. The outbreak was contained in large part because of aggressive vaccine mandates, which helped substantially increase childhood immunization rates in the community.

“We just missed it by a hair,” Dr. Nuzzo said. “Where we are now is worse than that.”

Mr. Kennedy has offered muted support for vaccination and has emphasized untested treatments for measles, such as cod liver oil. According to doctors in Texas, his endorsement of alternative treatments has contributed to patients delaying critical care and ingesting toxic levels of vitamin A.

Mr. Kennedy recently tapped a prominent figure in the anti-vaccine movement to work on a study examining the long-debunked theory that vaccines are linked to autism.

If the country does lose elimination status, Dr. Moss said, its unlikely that infection rates will resemble those of the pre-vaccine era, when measles infected nearly every child by age 15.

But it would be likely to mean more frequent and larger outbreaks that make life riskier for society’s most vulnerable: babies too young to be vaccinated, and immunocompromised people.

“There are direct consequences — the health tolls, the long-term health impacts,” Dr. Nuzzo said. “Measles outbreaks are like just incredibly costly and disruptive.”

“It’s also just an embarrassment. It puts the United States on par with some of the most resource-constrained settings in the world, and out of step with most high-income countries.”

Drug-resistant gonorrhea, a form of the widespread sexually transmitted infection, is considered an urgent health threat worldwide. The United States has just lost its ability to detect it.

Among the Centers for Disease Control and Prevention employees fired on Tuesday were 77 scientists who, among other work, gathered samples of gonorrhea and other S.T.I.s from labs nationwide, analyzed the genetic information for signs of drug resistance, and readied the samples for storage at a secure facility.

No other researchers at the agency have the expertise, or the software, to continue this work. The abrupt halt has stranded about 1,000 samples of gonorrhea and other sexually transmitted pathogens that had not yet been processed, and perhaps dozens more headed to the agency.

There are as many as 30 freezers full of samples that now have no custodians, said one senior C.D.C. official who spoke on condition of anonymity for fear of retaliation.

“We were just really shut down midair, like there was no warning,” the official said. “It was just completely unplanned and chaotic.”

The C.D.C.’s work on S.T.I.s had taken on greater urgency in the past few years as rates of new infections soared. More than 2.4 million new S.T.I.s were diagnosed in 2023, about one million more than 20 years ago.

Nearly 4,000 babies were born with congenital syphilis in 2023. About 280 were stillborn or died soon after.

“Whoever got rid of the lab just doesn’t understand how important the lab is,” said another senior C.D.C. official who spoke on condition of anonymity.

About 600,000 new gonorrhea cases were diagnosed in the United States in 2023. The bacteria that cause gonorrhea, called Neisseria gonorrhoeae, spread through sexual contact to the genitals, rectum and throat. Left untreated, it can cause infertility and sterility, blindness in infants or even death.

Gonorrhea has become resistant to nearly every available antibiotic, leaving a single class that still snuffs it out. The most powerful defense combines a shot of ceftriaxone with azithromycin, but some evidence hints that gonorrhea is evolving to sidestep even that treatment.

Over more than 25 years, the C.D.C. lab archived about 50,000 gonorrhea samples — the largest collection in the world — which allow scientists to track how the pathogen has changed over time. It’s not clear what will happen to the samples.

One new public health strategy makes it even more important for the nation to track gonorrhea, said Dr. Jenell Stewart, an infectious diseases physician at Hennepin Healthcare in Minneapolis.

In a bid to combat resurgent syphilis and chlamydia, the C.D.C. recommended last year that gay and bisexual men and transgender women take doxycycline, a widely used antibiotic, within 72 hours of unprotected sex.

Cities like San Francisco and Seattle that had earlier endorsed the practice, called doxy-PEP, have already seen drastic drops in the rates of those infections.

But researchers are worried that widespread use of doxycycline might increase resistance to the entire class of antibiotics, called tetracyclines. A few studies suggest there may be reason to worry.

Harvard University researchers last month analyzed more than 14,000 genetic sequences generated by C.D.C. researchers and found that the proportion of gonorrhea bacteria with antibiotic resistance increased to more than 35 percent last year, from less than 10 percent in 2020.

The federal scientists who produced that data and made it publicly available have all been fired. “Without public health money and infrastructure, I’m not sure who if anyone will take up the torch to monitor gonorrhea resistance,” Dr. Stewart said.

“This is a huge loss,” she added.

Dr. Stewart and a colleague spent two years preparing the protocol and an app to study doxy-PEP in cisgender women and monitor gonorrhea resistance.

The study was supported by the Adolescent Medicine Trials Network, whose funding was slashed last month.

At least five other grants to study doxy-PEP have been terminated, along with a variety of grants at the National Institutes of Health aimed at preventing S.T.I.s, including H.I.V.

Any lab can test for S.T.I.s, but commercial tests cannot determine whether gonorrhea will respond to available treatments. C.D.C. scientists developed the only such test, and provided funding and training to a few dozen labs on the sophisticated testing.

Samples were sent to the agency for confirmation. Without the agency scientists, testing for drug sensitivity will most likely cease, several experts said.

“We cannot have a national surveillance system without a national lab,” said one scientist who leads a C.D.C.-funded lab but did not wish to be identified without authorization to speak to the media.

C.D.C. scientists were also helping to develop alternatives to the nation’s outdated syphilis test. It cannot identify an active infection, only whether someone was ever infected. The agency has three large contracts to develop new rapid syphilis tests.

But without expertise and the samples from C.D.C. scientists, it’s unclear whether that work can continue, said a senior official with knowledge of the situation.

The fired scientists had about 1,400 years of field experience between them. The official said, “These were highly trained people that are not replaceable easily.”

The Trump administration on Friday rejected a Biden plan that would have required Medicare and Medicaid to cover obesity drugs and expanded access for millions of people.

Under the law that established Medicare’s Part D drug benefits, the program was forbidden from paying for drugs for “weight loss.” But the Biden administration’s proposal last November had attempted to sidestep that ban by arguing that the drugs would be allowed to treat the disease of obesity and its related conditions.

Expanding coverage of the drugs would have cost the federal government billions of dollars. The Congressional Budget Office estimated the federal expense would amount to about $35 billion over 10 years.

The decision announced Friday was part of a larger 438-page regulation updating parts of Medicare’s Part D drug benefits and Medicare Advantage, the private insurance plans that about half of Medicare beneficiaries now use.

Catherine Howden, a spokeswoman for the Centers for Medicare and Medicaid Services, said in an email that the agency believed that expanding coverage “is not appropriate at this time.” But she said the agency had not ruled out coverage and “may consider future policy options” for the drugs.

Medicare, the government insurance program for Americans over 65 and people with disabilities, does cover the weight-loss drugs for patients with diabetes, and for a much smaller subset of people who are obese and also have heart problems or sleep apnea.

The Biden plan would have extended coverage to patients who were obese but did not have those diseases. Medicare officials had estimated around 3.4 million more people would have chosen to take the drugs under the policy.

The most popular weight-loss drugs are made by Novo Nordisk, which sells its medicine as Wegovy for obesity and as Ozempic for diabetes, and by Eli Lilly, which sells its product as Zepbound for obesity and Mounjaro for diabetes.

Eli Lilly and Novo Nordisk now offer their products for $350 to $500 a month to patients who pay with their own money instead of going through insurance. But until recently, patients sometimes paid more than $1,300 a month.

Robert F. Kennedy Jr., the health secretary, has been vocal in his criticism of the weight-loss drugs, saying they are inferior to consuming healthy food.

The drugs have been shown in clinical trials to have benefits far beyond weight loss, like preventing heart attacks and strokes.

Proponents of expanded coverage have argued that the government’s expenditure on the drugs would at least partly pay for itself in the long run. Patients, they say, would become healthier and that would prevent expensive medical bills. It’s not clear yet whether such savings will materialize.

State Medicaid programs, which provide health care for the poor, can currently choose whether to cover the drugs, and some do. If the broader Biden policy had been finalized, coverage would have been required in every state.

The obesity drugs cost Medicare and Medicaid hundreds of dollars per patient each month, though the exact prices are secret.

Many employers and private health insurance plans do not cover the drugs. Some, including state employee benefit plans in North Carolina and West Virginia, dropped coverage of the drugs after their popularity surged, citing high costs.

Without insurance coverage, many patients on Medicare and Medicaid have been relying on inexpensive copycat versions of the drugs produced through a drug-ingredient mixing process known as compounding. These versions, which were allowed because the brand-name drugs were in short supply, can cost less than $200 a month. But regulators have ordered such sales to end soon because supply of the brand-name products has improved.

Republicans in Congress have expressed some interest in requiring Medicare to cover the drugs. The idea was included in a list of policy options produced by the House Budget Committee earlier this year. But it does not appear to be a major priority right now.

In an effort to reduce costs, Medicare has selected Novo Nordisk’s Wegovy for negotiations to lower prices under a law passed by a Democratic-controlled Congress in 2022. Those lower prices would kick in for eligible people in 2027, a change that has the potential to limit the long-term costs of coverage.

Carbon monoxide gas, which is invisible and odorless, can be fatal. It can kill people in their homes as they sleep, seeping undetected from generators. It can accumulate within the walls of closed garages, wafting from cars left running by residents seeking warmth or power in a storm.

On Thursday, another fatality by unintentional carbon monoxide poisoning was confirmed. Miller Gardner, the 14-year-old son of the longtime Yankees player Brett Gardner, died of carbon monoxide poisoning while on vacation with his family in Costa Rica. The authorities said contamination from machinery near their room at their resort could have been to blame.

While it is preventable, carbon monoxide poisoning is a leading cause of poisoning-related deaths in the United States.

Why is carbon monoxide dangerous?

Breathing in carbon monoxide causes the gas to build up in the blood and bind to hemoglobin, a protein in red blood cells that is responsible for transporting oxygen from the lungs to the tissues in the rest of the body.

When carbon monoxide binds to hemoglobin, it “kicks the oxygen off” the protein, and prevents tissues and organs from getting the oxygen they need to function properly, said Dr. Jason Rose, the chief of pulmonary, critical care and sleep medicine at the University of Maryland School of Medicine.

Exposure to carbon monoxide can also lead to inflammation and cellular damage to important organs, namely the heart and brain, said Dr. Anthony Pizon, chief of medical toxicology at the University of Pittsburgh Medical Center, who said he typically treats a couple of patients with carbon monoxide poisoning each month.

A person exposed to high concentrations of the gas for an extended period of time can lose consciousness and stop breathing, leading to death, Dr. Rose said. Inhaling the toxic gas can also cause your blood pressure to drop or can induce potentially fatal heart problems, he added. And those who survive carbon monoxide poisoning may experience long-term neurological problems, including worsened memory, problems with motor skills and symptoms of anxiety or depression, Dr. Rose said.

People might not realize that they have been exposed to carbon monoxide right away, Dr. Rose said, because some of the symptoms — headache, fatigue, nausea and vomiting — can look similar to the onset of the flu or another illness. Since the gas is colorless and odorless, Dr. Pizon said, it can also be difficult to know if there is an exposure.

And while the gas is considered highly toxic to everyone, Dr. Rose said that children, pregnant women, older adults and people with preexisting chronic illnesses such as heart disease are particularly vulnerable to getting sick after an exposure. So are those with breathing problems or anemia, which occurs when people have lowered levels of red blood cells or hemoglobin already.

If you think you’ve been exposed to carbon monoxide, immediately seek fresh air and call 9-1-1, Dr. Pizon said. The fire department can come to your home and help determine where the gas is coming from. And if you’re experiencing any symptoms, seek treatment right away at your nearest emergency room.

“This isn’t something you go to your primary doctor for,” Dr. Rose said.

At the emergency room, a health provider will give you pure oxygen through a ventilator or face mask, which will help your body flush out the carbon monoxide, Dr. Rose said.

Any home appliance that uses natural gas and burns fuel in your home, such as a stove, furnace, clothing dryer or gas-powered generator, can potentially leak carbon monoxide and cause poisoning if there is not proper ventilation, Dr. Pizon said. Make sure that all fuel-burning appliances are vented outside so that carbon monoxide cannot accumulate inside, he added. And if you are not sure whether your appliances are safely ventilated, call a technician to inspect them.

Many car engines release carbon monoxide as well, so don’t leave your car running, especially in an enclosed garage connected to your home.

Lastly, be sure to install carbon monoxide detectors, which can be purchased at any home improvement store, on every floor of your home, Dr. Pizon said. And change their batteries at least once a year. You can also purchase a portable carbon monoxide detector to use in hotels and lodging while traveling.

Most poisonings are reported in the winter.

More than 400 Americans die each year from unintentional carbon monoxide poisoning that is not linked to fire, according to the Centers for Disease Control and Prevention.

Poisonings are most often reported during the winter or in severe storms in which power goes out and people turn to generators, ovens and automobiles for warmth.

In 2021, when a freezing weather system swept parts of the United States, at least two people died and about 100 were sickened in Houston by carbon monoxide poisoning, and another four people died in Oregon, the authorities said.

In 2022, three people died of carbon monoxide poisoning caused by a faulty water heater in an Airbnb rental unit in Mexico City.

In December, 12 people were found dead of suspected carbon monoxide poisoning in a ski area in the Caucasus Mountains in Georgia. They were found in an area above a restaurant, where they were employed. A power generator had been plugged in and left inside after the restaurant lost power, the police said.

This article is part of Overlooked, a series of obituaries about remarkable people whose deaths, beginning in 1851, went unreported in The Times.

Katharine Dexter McCormick, who was born to a life of wealth, which she compounded through marriage, could have sat back and simply enjoyed the many advantages that flowed her way. Instead, she put her considerable fortune — matched by her considerable willfulness — into making life better for women.

An activist, philanthropist and benefactor, McCormick used her wealth strategically, most notably to underwrite the basic research that led to the development of the birth control pill in the late 1950s.

Before then, contraception in the United States was extremely limited, with bans on diaphragms and condoms. The advent of the pill made it easier for women to plan when and whether to have children, and it fueled the explosive sexual revolution of the 1960s. Today, the pill, despite some side effects, is the most widely used form of reversible contraception in the United States.

McCormick’s interest in birth control began in the 1910s, when she learned of Margaret Sanger, the feminist leader who had been jailed for opening the nation’s first birth control clinic. She shared Sanger’s fervent belief that women should be able to chart their own biological destinies.

The two met in 1917 and soon hatched an elaborate scheme to smuggle diaphragms into the United States.

Diaphragms had been banned under the Comstock Act of 1873, which made it a federal crime to send or deliver through the mail “obscene, lewd or lascivious” material — including pornography, contraceptives and items used for abortions. (The law, which still prohibits mailing items related to abortions, has received renewed attention since the federal right to abortion was overturned in 2022.)

McCormick, who was fluent in French and German, traveled to Europe, where diaphragms were in common use. She had studied biology at the Massachusetts Institute of Technology and was able to pose as a scientist in meetings with diaphragm manufacturers. “She purchased hundreds of the devices and hired local seamstresses to sew them into dresses, evening gowns and coats,” according to a 2011 article in M.I.T. Technology Review. “Then she had the garments wrapped and packed neatly into trunks for shipment.”

She and her steamer trunks made it through customs. If the authorities had stopped her, the article said, they would have found “nothing but slightly puffy dresses in the possession of a bossy socialite, a woman oozing such self-importance and tipping her porters so grandly that no one suspected a thing.”

From 1922 to 1925, McCormick smuggled more than 1,000 diaphragms into Sanger’s clinics.

After her husband died in 1947, she inherited a considerable amount of money, and she asked Sanger for advice on how to put it to use advancing research into contraception. In 1953, Sanger introduced her to Gregory Goodwin Pincus and Min-Chueh Chang, researchers at the Worcester Foundation for Experimental Biology in Massachusetts, who were trying to develop a safe, reliable oral contraceptive.

She was excited by their work and provided almost all the funding — $2 million (about $23 million today) — required to develop the pill. She even moved to Worcester to monitor and encourage their research. Pincus’s wife, Elizabeth, described McCormick as a warrior: “Little old woman she was not. She was a grenadier.”

The Food and Drug Administration approved the pill for birth control in 1960.

Katharine Moore Dexter was born into an affluent, socially activist family on Aug. 27, 1875, in Dexter, Mich., west of Detroit. The town was named for her grandfather, Samuel W. Dexter, who founded it in 1824 and maintained an Underground Railroad stop in his home, where Katharine was born; her great-grandfather, Samuel Dexter, was Treasury secretary under President John Adams.

Katharine and her older brother, Samuel T. Dexter, grew up in Chicago. Their mother, Josephine (Moore) Dexter, was a Boston Brahmin who supported women’s rights. Their father, Wirt Dexter, was a high-powered lawyer who served as president of the Chicago Bar Association and as a director of the Chicago, Burlington & Quincy Railroad. He also headed the relief committee after the Great Chicago Fire of 1871 and was a major real estate developer.

He died when Katharine was 14. A few years later, her brother died of meningitis while attending Harvard Law School. Those early deaths pointed her toward a career in medicine.

She attended M.I.T. and majored in biology, rare achievements for a woman of that era. She arrived with a mind of her own, and successfully challenged a rule that female students had to wear hats at all times, arguing that they posed a fire hazard in the science labs. She graduated in 1904 and planned to attend medical school.

But by then, she had started dating the dashing Stanley Robert McCormick, whom she had known in Chicago and who was an heir to an immense fortune built on a mechanical harvesting machine that his father had invented. As a young lawyer, he helped negotiate a merger that made his family a major owner of International Harvester; by 1909, it was the fourth largest industrial company in America, measured in assets.

McCormick persuaded Katharine to marry him instead of going to medical school. They wed at her mother’s château in Switzerland and settled in Brookline, Mass.

But even before they married, he had showed signs of mental instability, and he began experiencing violent, paranoid delusions. He was hospitalized with what was later determined to be schizophrenia, and remained under psychiatric care — mostly at Riven Rock, the McCormick family estate in Montecito, Calif. — until his death. She never divorced him and never remarried. They had no children.

Katharine McCormick spent decades mired in personal, medical and legal disputes with her husband’s siblings. They battled over his treatment, his guardianship and eventually his estate, as detailed in a 2007 article in Prologue Magazine, a publication of the National Archives. She was his sole beneficiary, inheriting about $40 million ($563 million in today’s dollars). Combined with the $10 million (more than $222 million today) she had inherited from her mother, that made her one of the wealthiest women in America.

As her husband’s illness consumed her personal life, McCormick threw herself into social causes. She contributed financially to the suffrage movement, gave speeches and rose in leadership to become treasurer and vice president of the National American Woman Suffrage Association. After women won the right to vote in 1920, the association evolved into the League of Women Voters; McCormick became its vice president.

In 1927, she established the Neuroendocrine Research Foundation at Harvard Medical School, believing that a malfunctioning adrenal gland was responsible for her husband’s schizophrenia. She provided funding for two decades and acquired an expertise in endocrinology that later informed her interest in the development of an oral contraceptive.

After the F.D.A. approved the pill, McCormick turned her attention to funding the first on-campus residence for women at M.I.T. When she studied there, women had no housing, one of several factors that discouraged them from applying. “I believe if we can get them properly housed,” she said, “that the best scientific education in our country will be open to them permanently.”

McCormick Hall, named for her husband, opened on the institute’s Cambridge campus in 1963. At the time, women made up about 3 percent of the school’s undergraduates; today, they make up about 50 percent.

By the time she died of a stroke on Dec. 28, 1967, at her home in Boston, McCormick had played a major role in expanding opportunities for women in the 20th century. She was 92.

Apart from a short article in The Boston Globe, her death drew little notice. The later obituaries of the birth-control researchers she had supported did not mention her role in their achievement.

In her will, she left $5 million to the Planned Parenthood Federation (more than $46 million today) and $1 million to Pincus’s laboratories (more than $9 million today). Earlier, she had donated her inherited property in Switzerland to the U.S. government for use by its diplomatic mission in Geneva. She left most of the rest of her estate to M.I.T.

The Trump administration announced on Thursday that it was laying off 10,000 employees at the Health and Human Services Department as part of a broad reorganization that reflects the priorities of the health secretary, Robert F. Kennedy Jr., and the White House’s drive to shrink the government.

The layoffs are a drastic reduction in personnel for the health department, which had employed about 82,000 people and touches the lives of every American through its oversight of medical care, food and drugs.

The layoffs and reorganization will cut especially deep at two agencies within the department that have been in Mr. Kennedy’s sights: the Food and Drug Administration and the Centers for Disease Control and Prevention. Those agencies are expected to lose roughly 20 percent of their staff members from the latest cuts alone.

Together with previous buyouts and early retirements spurred by Trump administration policies, the move will pare the health department down to about 62,000 employees, the agency said.

The restructuring is intended to bring communications and other functions directly under Mr. Kennedy. And it includes creating a new division called the Administration for a Healthy America.

“We’re going to do more with less,” Mr. Kennedy said, even as he acknowledged that it would be “a painful period for H.H.S.”

Mr. Kennedy asserted that rates of chronic disease rose under the Biden administration even as the government grew. But he did not provide data to back up his claim; experts say that rates of chronic disease have been rising for the past two decades, including under the first Trump administration. Two 2024 analyses of the issue used C.D.C. data from 2020.

The health secretary pitched the changes as a way to refocus the agency on Americans’ health, but did not outline any specifics on how he would reduce rates of diabetes, heart disease or any other conditions.

Inside the affected agencies, stunned employees struggled to absorb the news. Democrats and outside experts said the move would decimate agencies charged with protecting the health and safety of the American public, depriving it of the scientific expertise necessary to respond to current and future biological threats.

“In the middle of worsening nationwide outbreaks of bird flu and measles, not to mention a fentanyl epidemic, Trump is wrecking vital health agencies with the precision of a bull in a china shop,” said Senator Patty Murray, a Washington Democrat who has been a leader on health issues in Congress.

She called Mr. Kennedy’s comments about doing more with less an “absurd suggestion” that “defies common sense.” Her sentiments were echoed by several agency employees, who spoke on the condition of anonymity to avoid retribution.

They said they worried not for themselves, but for the country, expressing concern about what the layoffs would mean for public health and whether putting safety at risk was really what Americans wanted.

Under the plan, the C.D.C., which handles a wide range of health issues including H.I.V./AIDS, tobacco control, maternal health and the distribution of vaccines for children, would return to its “core mission” of infectious disease.

“Converting C.D.C. to an agency solely focused on infectious diseases takes us back to 1948 without realizing that in 2025, the leading causes of death are noncommunicable disease,” said Dr. Anand Parekh, who served in the health department during the Obama administration and is now the chief medical adviser at the Bipartisan Policy Center in Washington.

The C.D.C. will have its work force cut by about 2,400 employees, and will narrow its focus to “preparing for and responding to epidemics and outbreaks,” an H.H.S. fact sheet said. But it will also absorb the health department’s Administration for Strategic Preparedness and Response, which has 1,000 employees and was elevated to its own separate agency under the Biden administration during the coronavirus pandemic.

The reorganization will cut 3,500 jobs from the F.D.A., which approves and oversees the safety of a vast swath of the medications and food people eat and rely on for well-being, the fact sheet said. The cuts are said to be administrative, but some of the roles support research and monitoring of the safety and purity of food and drugs, as well as travel planning for inspectors who investigate overseas food and drug facilities.

The National Institutes of Health will lose 1,200 staff members, and the agency that administers Medicare and Medicaid is expected to lose 300.

All of those agencies tend to operate under their own authority, and Mr. Kennedy has been at odds with all of them. Mr. Kennedy assailed them, and other parts of the department, in a YouTube video.

“When I arrived, I found that over half of our employees don’t even come to work,” he claimed. “H.H.S. has more than 100 communications offices and more than 40 I.T. departments and dozens of procurement offices and nine H.R. departments. In many cases, they don’t even talk to each other. They’re mainly operating in silos.”

Mr. Kennedy’s move to take control of health communications is significant. Currently, agencies including the C.D.C., the N.I.H. and the F.D.A. manage their own communications with the press and the public.

During the first Trump administration, the C.D.C. clashed with the White House, which silenced agency scientists and took control of its public outreach about Covid-19. The agency’s chief spokesman quit in frustration last week, saying the C.D.C. has been muzzled since January, when Mr. Trump returned to office.

The 28 divisions of the Health and Human Services Department will be consolidated into 15 new divisions, according to a statement issued by the department. Mr. Kennedy announced the changes in his video. The staff cuts, reported earlier by The Wall Street Journal, are being made in line with President Trump’s order to carry out the Department of Government Efficiency’s drive to shrink the federal work force.

The plan also includes collapsing 10 regional H.H.S. offices into five.

The department notified union leaders of the “reduction in force” — known as a “RIF” in federal parlance — early Thursday morning by email. The message, obtained by The New York Times, said the layoffs would most likely take effect on May 27 and were “primarily aimed at administrative positions including human resources, information technology, procurement and finance.”

Democrats including Ms. Murray reacted with fury to the cuts. Representative Gerald E. Connolly of Virginia, the top Democrat on the Oversight and Government Reform Committee, said the cuts were troubling amid a bird flu outbreak and an uptick in measles cases.

“This is a grave mistake,” Mr. Connolly said in a statement, “and I have serious concerns about how this will impact Americans’ well-being now and long into the future.”

Republicans seemed to be taking more of a wait-and-see stance. Senator Bill Cassidy, Republican of Louisiana and the chairman of the committee that oversees health, said he had breakfast with Mr. Kennedy on Thursday. Mr. Cassidy suggested he was open to the reorganization but expected the two “would have more conversations” about specific cuts as their effects became clearer.

Doreen Greenwald, the president of the National Treasury Employees Union, which represents 18,500 H.H.S. staff members across the country, issued a statement vowing to “pursue every opportunity to fight back on behalf of these dedicated civil servants.”

“The administration’s claims that such deep cuts to the Food and Drug Administration and other critical H.H.S. offices won’t be harmful are preposterous,” Ms. Greenwald said.

Xavier Becerra, who served as health secretary under President Joseph R. Biden Jr., issued a statement saying the cuts would most likely downgrade services to elderly and disabled people, and those with mental health challenges, in addition to preparedness for health crises.

“This has the makings of a man-made disaster,” he said on social media.

Mr. Kennedy suggested in the video that the changes would help his team get more access to data. That prospect has been worrisome to his critics, given Mr. Kennedy’s long history of manipulating figures to advance arguments about what he contends are the risks of vaccines that have widely been deemed safe.

“In one case,” Mr. Kennedy said, “defiant bureaucrats impeded the secretary’s office from accessing the closely guarded databases that might reveal the dangers of certain drugs and medical interventions.”

Mr. Kennedy said the new division he is creating, the Administration for a Healthy America, would combine a number of agencies focused on substance abuse treatment and chemical safety, as well as the agency that administers courts that handle federal claims over vaccine injuries.

“We’re going to consolidate all of these departments and make them accountable to you, the American taxpayer and the American patient,” he said. “These goals will honor the aspirations of the vast majority of existing H.H.S. employees who actually yearn to make America healthy.”

Michael Gold contributed reporting.

A steadfast figure in the anti-vaccine movement who has helped shape Health Secretary Robert F. Kennedy Jr.’s thinking on a possible link to autism has joined his department to work on a study examining the long-debunked theory, according to people familiar with the matter.

The new analyst, David Geier, has published numerous articles in the medical literature attempting to tie mercury in vaccines to autism. In 2012, state authorities in Maryland found that he had been practicing medicine without a license alongside his father, Mark Geier, who was a doctor at the time.

Maryland authorities also suspended Mark Geier’s medical license following claims that he endangered children with autism and exploited their parents, according to state records.

Federal judges have rejected their research on autism and vaccines as too unreliable to stand up in court.

David Geier’s new government role has stunned public health experts, who had already expressed concerns about Mr. Kennedy’s decisions to cancel a long-held vaccine meeting and to cut grants focused on understanding vaccine hesitancy.

In addition, David Geier’s involvement in government research heightens their fears that vaccine confidence could be further eroded, especially after Mr. Kennedy’s recent embrace of questionable alternative treatments for measles during the sprawling outbreak in Texas.

“If we increase vaccine hesitancy and immunization rates go down further, we will see more vaccine-preventable disease outbreaks,” said Dr. Christopher Beyrer, director of the Duke Global Health Institute. “That’s how it works.”

Several experts said that appointing David Geier to work on a study of vaccine safety preordains the outcome — like having a basketball referee show up in one team’s jersey.

“You’d think you’d want a fresh eye,” said Edward L. Hunter, a former head of the Washington office of the Centers for Disease Control and Prevention.

“This isn’t a fresh eye. They have already published their results, and spending all this time and money is not going to help anyone. I am quite certain they’ll come to the same conclusion.”

An official with Mr. Kennedy’s Department of Health and Human Services declined to comment. Two White House spokesmen did not respond to a request for comment. David Geier did not reply to emails or calls requesting comment.

Mary Holland, chief executive of Children’s Health Defense, the anti-vaccine nonprofit Mr. Kennedy ran until his presidential bid, praised David Geier on its website on Wednesday, describing him as “a brilliant, extremely knowledgeable researcher with deep expertise on mercury.”

(Over the weekend, federal officials ordered the nonprofit to remove a mock C.D.C. web page suggesting a link between vaccines and autism.)

David Geier is listed in the Department of Health and Human Services directory as a “senior data analyst.” News of his role in the agency was initially reported by The Washington Post.

Earlier this month, federal officials announced plans for a large study to re-examine whether there was a connection between vaccines and autism. Mr. Trump has voiced support for H.H.S. officials who wanted to revisit the issue, citing increases in autism diagnoses in children over the decades.

About 1 in 36 children have an autism diagnosis, according to C.D.C. data collected in 11 states, compared with 1 in 150 children in 2000.

Many scientists believe the rise is due in part to increased awareness of the disorder and changes in how it is diagnosed by medical professionals, though genetic and environmental factors could be playing a role as well.

The Senate confirmed Mr. Kennedy largely because he won over the chairman of the Senate health committee, Bill Cassidy, Republican of Louisiana, who is a medical doctor and strong proponent of childhood vaccines.

Mr. Cassidy has said that further research into any supposed link between vaccines and autism would be a waste of money and a distraction from studies that might shed light on the “true reason” for the rise in autism rates.

On Thursday, Mr. Cassidy said he wanted confirmation of David Geier’s role, aside from news reports. He mentioned that he had breakfast with Mr. Kennedy on Thursday but said the topic did not come up.

At one of his confirmation hearings, Mr. Kennedy shot back at Mr. Cassidy, citing a study from an ecosystem of vaccine critics that he said proved a connection between vaccines and autism.

David Geier comes from a similar circle of researchers. Along with his father, he played a formative role in Mr. Kennedy’s thinking.

Mr. Kennedy interviewed David Geier for an essay in 2005, “Tobacco Science and the Thimerosal Scandal,” in which he accused the C.D.C. of deliberately hiding vaccine data, under chapter headings like “Conspiracy” and “The Cover-Up.”

Mr. Kennedy described the Geiers’ belief that thimerosal, a mercury-containing preservative used in some vaccines, was linked to childhood autism. The preservative has since been removed from most childhood vaccines but is still used in some flu shots.

In a Rolling Stone article called “Deadly Immunity,” Mr. Kennedy credited the Geiers with being among the few who had gained access to C.D.C. vaccine data, which he said they used to “demonstrate a powerful correlation between thimerosal and neurological damage in children.” (The magazine later withdrew the article, but did not elaborate.)

Almost a decade later, in Mr. Kennedy’s book, “Thimerosal: Let The Science Speak,” he paid homage to the Geiers, mentioning them nearly 250 times. He called them a “father-and-son team of independent medical researchers” who had “published extensively on the topic of thimerosal and its potential link to neurodevelopmental disorders, particularly autism.”

Mr. Kennedy acknowledged that the two had become “lightning rods of controversy in the vaccine safety debate.”

“The Geiers have published no fewer than thirteen epidemiological studies of the associations between Thimerosal and health effects in U.S. populations, employing accepted statistical practices,” Mr. Kennedy wrote in the book.

On a podcast in 2022, Mr. Kennedy credited the Geiers’ research for showing that vaccines “had nothing to do with” a decline in infectious diseases over decades. “It was all an illusion,” Mr. Kennedy said, attributing the decrease to improving sanitation and nutrition.

The Geiers’ work has been repeatedly discredited by other scientists and federal court decisions.

An extensive review of the purported link between vaccines and autism in 2004 by the Institute of Medicine, an elite group of doctors and researchers, panned the Geiers’ studies. The review found their work to be marred by flaws “making their results uninterpretable.”

The institute’s report on a connection with the measles shots said: “The committee concludes that the evidence favor rejection of a causal relationship between M.M.R. vaccine and autism.”

In 2011, the Maryland Medical Board accused David Geier of practicing medicine without a license alongside his father at a Rockville, Md., clinic for children with autism.

One mother of a 10-year-old boy with autism balked when David Geier reportedly ordered 24 different blood tests for her son.

His father, Mark Geier, lost his medical license in 2012. Records in that case indicate that both father and son promoted a theory that thimerosal caused autism.

State authorities found that the Geiers had offered treatment with puberty-blocking drugs. To some patients, they offered chelation, a procedure to remove heavy metals from the blood, records show. David Geier was assessed a $10,000 fine.

Judges have rejected the Geiers’ efforts to serve as experts on vaccine safety in court. Records show that judges challenged the father-son team’s billings for hundreds of thousands of dollars related to services they provided as experts for a specialized vaccine injury court.

The judges cited David Geier’s lack of qualifications, which include a bachelor’s degree in biology, and raised concerns about his father’s credibility.

Judge George L. Hastings Jr. said in 2016 that David Geier was not qualified to render an expert opinion in a National Vaccine Injury Compensation court case.

Judge Hastings said his report “is neither useful nor relevant, because he is not qualified as an expert concerning the matters he discusses.”

In a review of two Geier studies this week, Jeffrey S. Morris, director of the division of biostatistics at the University of Pennsylvania, said he found what appeared to be a numerical sleight of hand that made it appear that vaccines caused a spike in autism.

“When I look at these two studies, they are so fatally flawed that I have serious concerns that any study that they’re going to design is going” to be rigorous enough, he said, “to yield valid results.”

To Mr. Hunter, formerly of the C.D.C., the decision to spend federal funds on a new study of a debunked theory would come at the cost of a meaningful discovery.

Since he became health secretary, Mr. Kennedy has presided over cutbacks involving research into nearly every aspect of health care and diseases. On Thursday, he announced a massive reorganization and reduction in the work force from 82,000 to 62,000.

“To me, the big shame is that with budget cuts, we are not ramping up research into what is actually causing autism,” Mr. Hunter said. “And if you are worried about vaccine-preventable disease, this is such a clear setback.”

Michael Gold contributed reporting from Washington. Alain Delaquérière contributed research. Jeremy Singer-Vine provided data analysis.

The Supreme Court heard arguments on Wednesday in a case arising from South Carolina’s attempt to deny funding to Planned Parenthood. But the question the justices grappled with was a relatively narrow one, focused on whether individuals may sue the state to obtain medical services from Planned Parenthood unrelated to abortion.

In 2018, Gov. Henry McMaster of South Carolina, a Republican, ordered state officials to deny Medicaid funds to Planned Parenthood, saying that “payment of taxpayer funds to abortion clinics, for any purpose, results in the subsidy of abortion and the denial of the right to life.”

Medicaid gives federal money to states to provide medical care for poor people, but it sets some conditions. One is that eligible participants may receive assistance from any provider qualified to perform the required services.

Abortions are banned in South Carolina after six weeks of pregnancy, and, even then, federal law prohibits the use of Medicaid funding except in life-threatening circumstances or in cases of rape or incest. But Planned Parenthood clinics in Charleston and Columbia provide services unrelated to abortion, including counseling, physical exams, contraception and screenings for cancer and sexually transmitted infections.

Planned Parenthood and a patient who sought contraception sued under a federal civil rights law, and a federal trial judge blocked the South Carolina directive, saying that it ran afoul of Medicaid’s requirement that patients may choose any qualified provider.

The litigation that followed was convoluted and circuitous, focusing largely on whether that provision created a right that individuals could enforce by filing lawsuits. The Supreme Court has said that federal laws like Medicaid, which give money to states but only if they accept certain conditions, must “unambiguously confer individual federal rights” to give affected individuals the right to sue.

That is a hard test to meet, and the court has ruled that it has been satisfied only rarely, most recently in 2023 in Health and Hospital Corporation of Marion County v. Talevski, a case concerning nursing homes. The statute at issue in that case repeatedly referred to “rights” as such, while the Medicaid provision in the new case used different language.

It said people seeking medical services “may obtain such assistance from any institution” that is “qualified to perform the service or services required.”

Nicole A. Saharsky, a lawyer for Planned Parenthood, acknowledged that the standard was strict.

“It is a high bar to find that Congress put in place an individually enforceable right,” she said. “What we’re saying is that this provision meets the bar.”

Kyle D. Hawkins, a lawyer for the Trump administration, disagreed, saying the Medicaid provision lacked the required “unmistakable rights-creating language.”

Under the Biden administration, the government had taken the opposite position, which Mr. Hawkins acknowledged.

“With the change in administration,” he said, “the federal government re-evaluated its position in this case, and we believe that the view we’re advancing today is the best reading of the statute.”

The justices discussed at length whether Congress had to use “magic words” to allow people to sue. John J. Bursch, a lawyer with the Alliance Defending Freedom, a conservative Christian group that represents South Carolina, proposed a series of words Congress could use to grant an unambiguous right to sue.

“The list I would give you is rights, entitlement, privilege and immunities,” he said, adding that they did not amount to magic words.

In response, Justice Brett M. Kavanaugh said, “I’m not allergic to magic words because magic words, if they represent the principle, will provide the clarity that will avoid the litigation that is a huge waste of resources for states, courts, providers, beneficiaries and Congress.”

Justice Elena Kagan said the language in the Medicaid law could hardly be plainer. “The state has to ensure that individuals have a right to choose their doctor,” she said. “That’s what this provision is.”

Last year, a unanimous three-judge panel of the U.S. Court of Appeals for the Fourth Circuit, in Richmond, Va., ruled that the suit could proceed.

“This case is, and always has been, about whether Congress conferred an individually enforceable right for Medicaid beneficiaries to freely choose their health care provider,” Judge J. Harvie Wilkinson III wrote for the panel. “Preserving access to Planned Parenthood and other providers means preserving an affordable choice and quality care for an untold number of mothers and infants in South Carolina.”

He added that “this decision is not about funding or providing abortions.”

Abortion was mentioned only in passing in Wednesday’s argument in Medina v. Planned Parenthood South Atlantic, No. 23-1275, and the case did not turn on the state’s reason for trying to disqualify Planned Parenthood. But Ms. Saharsky said the dispute presented issues beyond a technical one about who can sue.

Congress, she said, had tried to send a message: “We want people on Medicaid who are insured through Medicaid to have the same right that people who have private insurance enjoy because it’s so foundational to individual dignity and individual autonomy.”