A measles outbreak that has spread over a swath of West Texas, killing one child, shows no signs of slowing, according to data announced on Tuesday by state health officials.

The Texas Department of Health reported that since late January, nearly 160 people have contracted measles — 20 more cases than reported on Friday — and 22 have been hospitalized.

The Centers for Disease Control and Prevention announced on Tuesday that it would send some of its “disease detectives” to Texas, one of the first steps the new administration has taken to help manage the outbreak.

The news comes amid criticism of federal officials for underplaying the need for immunizations with the measles-mumps-rubella vaccine, one of the most important tools in quelling an outbreak.

Robert F. Kennedy Jr., the health and human services secretary and a prominent vaccine skeptic, published an opinion piece on Sunday night acknowledging that vaccines protect children from measles and urged parents to talk with their doctors “to understand their options to get the M.M.R. vaccine.”

“The decision to vaccinate is a personal one,” he wrote.

In a prerecorded interview that aired on Fox News on Tuesday, Mr. Kennedy said that the federal government was shipping doses of vitamin A to Gaines County, in West Texas, and helping to arrange ambulance rides.

H.H.S. previously said officials were shipping doses of the vaccine for measles, mumps and rubella, but the health secretary did not mention vaccination.

Doctors had seen “very, very good results,” Mr. Kennedy claimed, by treating measles cases in Texas with a steroid, budesonide; an antibiotic called clarithromycin; and cod liver oil, which he said had high levels of vitamin A and vitamin D.

While physicians sometimes administer doses of vitamin A to treat children with severe measles cases, cod liver oil is “by no means” an evidence-based treatment, said Dr. Sean O’Leary, chair of the American Academy of Pediatrics Committee on Infectious Diseases.

Dr. O’Leary added that he had never heard of a physician using the supplement against measles.

In comments that seemed to be about conventional safeguards against measles, Mr. Kennedy said, “We’re going to be honest with the American people for the first time in history about what actually — about all of the tests and all of the studies, about what we know, what we don’t know.”

“We’re going to tell them, and that’s going to anger some people who want an ideological approach to public health.”

The dimensions of the current outbreak are unclear. The official case number in the Texas outbreak is most likely an undercount, said Katherine Wells, the director of public health in Lubbock, Texas.

The outbreak has largely spread within a community of Mennonites in Gaines County, who historically have had lower vaccination rates and often avoid interacting with the health care system.

Ms. Wells said she believed many of those families did not seek medical attention for measles and have not been accounted for in the state’s official numbers.

“I think it’s probably in the hundreds,” she said. “We know that some of their schools were closed with lots of sick children, but we don’t know who those children were.”

Last year, roughly 82 percent of the county’s kindergarten population had received the vaccine for measles, mumps and rubella. Experts say that at least 95 percent of people in a community must be vaccinated in order to stave off outbreaks.

Declining vaccination rates in the United States have left growing pockets of vulnerable children, making it more likely that an outbreak will jump from one unvaccinated group to another.

Just 93 percent of kindergarten students nationwide had received the vaccine for measles, mumps and rubella in the 2023-24 school year, down from 95 percent before the pandemic.

“We’ve benefited greatly as Americans by the fact that these communities have been spaced out,” said Michael Mina, formerly an epidemiologist at Harvard and now chief medical officer at eMed.

“A case in one of them can ignite cases in all of them, because you’re no longer benefiting from this space,” he said.

In Texas, measles cases have been confirmed in nine counties, many of which have vaccination rates below federal recommendations.

About 80 percent of kindergarten students in one of the public school districts in Terry County, which neighbors Gaines, were vaccinated for measles, according to recent state data. That county reported 22 cases of measles Tuesday.

A county in New Mexico that borders Gaines County has reported nine measles cases.

While most measles cases resolve in a few weeks, in rare cases the virus can cause pneumonia, making it difficult for patients, especially children, to get oxygen into their lungs, or brain swelling, which can lead to blindness, deafness and intellectual disabilities.

About one in five people who catch measles will be hospitalized, according to the C.D.C.

The virus also weakens the immune system in the long term, making its host more susceptible to future infections. A 2015 study found that before the M.M.R. vaccine was widely available, measles may have been responsible for up to half of all infectious disease deaths in children.

Sheryl Gay Stolberg contributed reporting.