The Trump administration, moving quickly to clamp down on health and science agencies, has canceled a string of scientific meetings and instructed federal health officials to refrain from all public communications, including upcoming reports focused on the nation’s escalating bird flu crisis.

Experts who serve on outside advisory panels on a range of topics, from antibiotic resistance to deafness, received emails on Wednesday telling them their meetings had been canceled.

The cancellations followed a directive issued on Tuesday by the acting director of the federal Department of Health and Human Services, who prohibited the public release of any public communication until it had been reviewed by a presidential appointee or designee, according to federal officials and an internal memo reviewed by The New York Times.

The directive enjoins the public release of “regulations, guidance documents, and other public documents and communications,” including any “notice,” “grant announcement,” news releases, speaking engagements or official correspondence with public officials, until they have received approval.

The new stricture applies to messages to email groups and to social media posts, and included a ban on announcements to The Federal Register, without which many official processes cannot continue. Some notices sent by the Biden administration in its final week were quickly withdrawn.

The cancellations and communications crackdown sent a chill through employees of the Centers for Disease Control and Prevention and the broader scientific community. The directive was first reported by The Washington Post.

Representatives of the C.D.C. and the Food and Drug Administration declined to comment. The moratorium is to continue through Feb. 1.

The fallout was immediate.

Officials at the C.D.C. had been prepared to publish an issue of the influential Morbidity and Mortality Weekly Report on Thursday that included several items related to the widening bird flu outbreak on dairy and poultry farms.

The weekly reports have been called the “holiest of the holy,” a crucial means of communication about developments in public health. This week’s publication is now held up as a result of the order, according to two federal health officials who spoke on condition of anonymity because they were not authorized to speak publicly.

Upcoming meetings of outside advisory panels on health issues have been canceled, according to panel members, who spoke anonymously for fear of retribution. Meetings to review grant proposals submitted to the National Institutes of Health were scrubbed, for example.

Members of the Presidential Advisory Council for Combating Antibiotic-Resistant Bacteria were told that their two-day meeting, scheduled for next Tuesday and Wednesday, had been canceled “as the new Administration considers its plan for managing federal policy and public communications.”

Those who had registered in advance for a celebratory dinner were told they would be “fully reimbursed within 48 hours” of receiving the email.

The directive was signed by Dr. Dorothy Fink, acting secretary of the Department of Health and Human Services. The confirmation hearing for Robert F. Kennedy Jr., whom President Trump has nominated to lead the department, is not expected for at least another week.

The administration has yet to name an acting director for the C.D.C. or an acting commissioner at the Food and Drug Administration, usually among the first moves by an incoming administration.

The communications pause accompanies a spate of other changes facing federal employees since Mr. Trump’s inauguration on Monday, including a hiring freeze, an end to remote work and the shuttering of diversity, equity and inclusion offices and programs.

Late on Wednesday, Dr. Fink issued another directive aimed at ending diversity and inclusion efforts at H.H.S. and warned against attempting to “disguise these programs by using coded or imprecise language.” Her letter also encouraged employees to report on colleagues who were not compliant.

Former federal officials said it was not unusual for a new administration to limit communication during the initial transition, but the scope and duration of the latest pause were unexpected.

Staff members of the incoming Trump administration did not use the transition period to meet with federal health officials and to familiarize themselves with the agencies.

And while a pause on communications is not out of the ordinary, previous administrations have not restricted scientific publications like the M.M.W.R. or health guidelines because of their critical importance to public welfare.

“It’s not unusual for a new administration to want to centralize communication,” said Dr. Richard Besser, the chief executive of the Robert Wood Johnson Foundation and a former acting director of the C.D.C.

“It is unusual to pause all communication from an agency where one of its critical responsibilities is keeping the public informed,” he added.

Privately, several federal officials said they were confused about whether the restriction on communications with The Federal Register included health data. Some officials seemed unaware of the restrictions at all.

Much of the concern centered on the C.D.C., whose responsibilities certainly include public communications. The agency, for example, recently made doctors and patients aware of potential health risks about an emerging version of mpox and an outbreak of Marburg disease in Rwanda.

The agency has offered findings on the mental health effects of the pandemic on health care providers and new guidelines extending the recommendation for pneumococcal vaccines, and has warned of an increase in the incidence of tularemia, a rare infectious disease, in the United States.

State and city health officials rely on C.D.C. notices to make decisions for their communities, such as when to ramp up flu testing or which disease symptoms to keep an eye out for, said Chrissie Juliano, executive director of the Big Cities Health Coalition, which represents leaders of urban public health departments.

While much of that information can be delayed a few days, she said she hoped that the administration had a plan for disseminating more pressing public health information, especially in relation to the bird flu outbreak.

In the past year, the bird flu virus, called H5N1, has affected dozens of animal species and more than 35 million wild and commercial birds, resulting in soaring egg prices. It has also infected at least 67 people; the country recorded its first bird-flu-related human death in December.

“Can something like the bird flu turn on a dime in 10 days?” Ms. Juliano said. “Yes. I would hope that if those signals are seen at the federal level, information is going to get out.”

Dr. Ashish Jha, dean of the Brown University School of Public Health and the Biden administration’s former Covid czar, said the pause on communications was most likely a product of the Trump administration’s “particularly bumpy” transition into the White House, rather than a coordinated effort to withhold information.

Still, public health experts are wary of any changes to access of federal health data. Memories from Mr. Trump’s last term, during which political appointees repeatedly meddled in C.D.C. reports and doctored guidance documents, are still raw.

“I think if it goes anywhere beyond Feb. 1, then we have a much more serious problem,” Dr. Jha said.