C.D.C. Posts, Then Deletes, Data on Bird Flu Spread Between Cats and People

The data, which appeared fleetingly online on Wednesday, confirmed transmission in two households. Scientists called on the agency to release the full report.

Cats that became infected with bird flu might have spread the virus to humans in the same household and vice versa, according to data that briefly appeared online in a report from the Centers for Disease Control and Prevention but then abruptly vanished. The data appear to have been mistakenly posted but includes crucial information about the risks of bird flu to people and pets.

In one household, an infected cat might have spread the virus to another cat and to a human adolescent, according to a copy of the data table obtained by The New York Times. The cat died four days after symptoms began. In a second household, an infected dairy farmworker appears to have been the first to show symptoms, and a cat then became ill two days later and died on the third day.

The table was the lone mention of bird flu in a scientific report published on Wednesday that was otherwise devoted to air quality and the Los Angeles County wildfires. The table was not present in an embargoed copy of the paper shared with news media on Tuesday, and is not included in the versions currently available online. The table appeared briefly at around 1 p.m., when the paper was first posted, but it is unclear how or why the error might have occurred.

The virus, called H5N1, is primarily adapted to birds, but it has been circulating in dairy cattle since early last year. H5N1 has also infected at least 67 Americans but does not yet have the ability to spread readily among people. Only one American, in Louisiana, has died of an H5N1 infection so far.

The report was part of the C.D.C.’s prestigious Morbidity and Mortality Weekly Report, which, until two weeks ago, had regularly published every week since the first installment decades ago. But a communications ban on the agency had held the reports back, until the wildfire report was published on Wednesday.

Experts said that the finding that cats might have passed the virus to people was not entirely unexpected. But they were alarmed that the finding had not yet been released to the public.