Just days after publishing important new guidance about the transmission of the Coronavirus through the air, the Centers for Disease Control and Prevention on Monday withdrew the advice, saying only that it was “accidentally published” on the agency’s website.

The rapid reversal sparked panic among scientists and raised questions once again about the credibility of the first World Health Agency, even as President Trump and top health officials sought to undermine CDC scientists.

The president is facing elections, the outcome of which may affect public perception of his handling of the Coronavirus pandemic.

The shift has reached as the number of virus-related deaths in the United States approaches 200,000. Tens of thousands of new infections are reported every day, and experts fear a resurgence as the cold weather approaches and more time is spent indoors.

The new document recognized for the first time that the virus is spreading primarily through the air, a declaration with immediate implications for how people protect themselves at home and how ventilation should be designed in schools, offices, hospitals and other public buildings.

Experts familiar with the incident said on Monday that the latest reversal appeared to be a real flaw in the agency’s scientific review process, and not the result of political interference. Officials said the agency will soon publish revised guidance.

“We are reviewing our process and tightening standards to review all guidance and updates before they are posted on the CDC website,” said Jason MacDonald, a spokesperson for the agency.

However, the reversal drew a rebuke from even the CDC’s staunchest supporters. “It’s not something that instills a lot of confidence, is it?” Said Dr. Carlos Del Rio, an infectious disease expert at Emory University. “It doesn’t help at all.”

Other scholars said that it was difficult to understand how a document of such importance to public health could be published without careful examination, given how accurate the agency’s procedures are today.

“At this time, everyone knows that the stakes are very high in terms of scientific communication,” said Dr. Abrar Karan, MD, internal medicine physician at Harvard Medical School.

The CDC suffered a series of blows to its reputation as the pandemic spread in the United States. Only in April, for example, did officials recommend face coverings to the public, after initially saying masks were not necessary.

The CDC said in August that people who have had close contact with an infected person but no symptoms do not need to be tested for infection. But last week, after the New York Times reported that the directive had been dictated by administration officials and not by scientists, the agency reversed its position and said that all contacts of the infected should be tested regardless of symptoms.

The reversal came after HHS spokesperson Michael R Caputo took time off to “focus on his health and the well-being of his family” after federal scientists were accused of “strife” in a bizarre Facebook talk. Dr. Paul Alexander, a consultant to Mr. Caputo who has been highly critical of CDC research, is leaving the department as well.

Trump last week slammed the agency’s director, Dr. Robert Redfield, after Dr. Redfield told a congressional hearing that the vaccine would not be widely available until the middle of next year. The president said, “It’s just incorrect information.”

The constant disagreements make it even more difficult for the general public who are now looking at these directions and asking, “What the hell does this mean?” Dr. Karan said.

The latest incident is related to the spread of the virus through the air through droplets and aerosols, which are small particles that contain the virus that can stay aloft for long periods and travel more than six feet.

Scientists have been aware from the start of the epidemic that the coronavirus can be spread through respiratory droplets that infected people sneeze or cough. Only recently have health agencies like the World Health Organization recognized the role of a floating aerosol, which is expelled by speech, breathing or even singing.

The new document released by the Centers for Disease Control and Prevention described both as airborne transmission, but officials have never previously detailed an expansionary role for aerosols.

The CDC said in the document published on Friday that the virus spreads through “respiratory droplets or small particles, such as those found in aerosols, which are produced when an infected person coughs, sneezes, sings, speaks, or breathes.”

The agency added that these particles may be inhaled and may lead to infection: “It is believed that this is the main way the virus spreads.”

“Airborne viruses, including Covid-19, are among the most contagious and easily spread,” said Saskia Popescu, a hospital epidemiologist at George Mason University – a statement that has enormous implications for how hospitals care for coronavirus patients.

Airborne viruses may require that patients be isolated in so-called negative pressure rooms, which prevent the virus from escaping, and that health care workers wear N95 masks at all times.

“The challenge then will be that we cannot place every patient in negative pressure rooms,” said Dr. Popescu.

She added that if hospitals’ ventilation and infection control systems provide insufficient protection against the virus, hospitals will seed more infections.

“My gut tells me that’s why they did, really,” said Dr. Popescu. “I think they understand that you can’t throw out ‘air’ randomly. It has very dangerous implications for hospitals.”

Scientific research to date indicates that aerosols are primarily important in certain places – often in crowded, poorly ventilated indoor spaces, such as many bars, clubs, gyms, and restaurants.

In the document published on Friday, the agency warned that the virus may remain suspended in the air for long periods and travel distances exceeding six feet.

Earlier this summer, scientists isolated the live virus from an aerosol collected at a distance of seven and 16 feet from an infected patient in the hospital. Scientists said the airborne spread may explain many of the so-called “superspreader” events, such as a cluster of cases following the practice of choir in Washington state, and why southern states saw a spike in infections this summer as people stayed indoors in air conditioners. Environments.

On Sunday, the researchers noted that the agency had updated its description of how the virus was transmitted to say that the pathogen is spread primarily through the air. Many welcomed the CDC’s recognition of these risks, and their endorsement of indoor air filters.

“A lot of people spend hours cleaning places, and I think it’s a lot of exaggeration, quite frankly,” said Dr. Del Rio.

But the new language disappeared Monday morning, and official advice reverted to an earlier description of the respiratory droplet spread. “A draft copy of the proposed changes to these recommendations was published by mistake on the agency’s official website,” the agency said.

The document was posted on the CDC’s website “prematurely” and will be posted after review, according to a federal official familiar with the matter.

More than 200 experts studying aerosols called on the World Health Organization in July to review evidence of transmission of the Coronavirus via aerosols.

The World Health Organization acknowledged that this route appears to contribute significantly to the spread of the epidemic, but experts differ in its importance for the heavy respiratory droplets that sneeze or cough to infected patients.

“We do not have epidemiological evidence at the moment to say that it is one more than the other,” said Dr. Popescu.

Some experts said that regardless of which is more important – drops or aerosols – what matters is how people should protect themselves.

“I think aerosols are very important, important enough that public health guidelines put them front and center,” said Lynsey Marr, an expert on airborne viruses at Virginia Tech University. “I hope he’s back in some way that recognizes the importance of aerosols.”