First bird flu case in a child in the U.S. confirmed in California

A child in California has tested positive for bird flu, the first case of a child in the United States becoming infected with the H5N1 virus, federal officials said Friday.

The Centers for Disease Control and Prevention said it is conducting additional tests to determine whether the virus is linked to the version causing a growing outbreak in U.S. dairy cows or the version spread by wild birds that has infected poultry flocks globally.

The child had no known contact with an infected animal and is recovering at home in Alameda County, according to California health officials. Public health experts are investigating a possible exposure to wild birds, the state health department said.

Earlier testing by the California Department of Public Health showed the child, who had mild respiratory symptoms, was positive for an H5N1 bird flu infection. Repeat testing for the virus four days later was negative for H5N1, state officials said, and specimens were sent to the CDC for additional testing.

The California child is the second youngster infected with bird flu in North America. Last week, health officials in British Columbia reported that a Canadian teenager was infected with bird flu and was hospitalized after experiencing difficulty breathing.

The two cases are concerning because the route of transmission is unlike all but one of the other 54 human cases of bird flu reported in the United States this year. The other infections occurred in workers on dairy or poultry farms. All experienced mild illness, mostly pink eye. No one was hospitalized.

Human infections with H5N1 bird flu virus without an identified animal exposure are uncommon, according to the CDC. The rare instances have occurred mostly in other countries.

“It’s clear that H5N1 is not going away any time soon,” said Katelyn Jetelina, a California epidemiologist who writes a weekly newsletter on infectious diseases. “The more we let it run rampant, the more cases we will have and the more chances we give this virus to mutate.”

To date, none of the H5N1 bird flu cases reported in the United States have been transmitted between people.

The previously healthy Canadian teen remains in critical condition but is stable, a spokesman for British Columbia’s provincial health officer said in an email Friday. No further cases have been identified after follow-up with the teen’s friends, family and health-care workers, he said.

Canadian officials have said the teen was probably infected with the virus after being exposed to an infected bird or other animal, but they do not know with certainty and may never be able to identify the source. Canadian and U.S. officials have confirmed that the teen’s infection is related to the H5N1 viruses causing ongoing poultry outbreaks in British Columbia.

In California, no person-to-person spread of the virus has been detected or is suspected, the state health department said. All of the child’s close family members experiencing cold and flu symptoms similar to those of the child have tested negative for bird flu.

Public health officials said other individuals who had contact with the child are being notified and offered preventive treatment and testing. The child had attended day care with mild cold and flu symptoms before being tested for bird flu.

The H5N1 outbreak has spread rapidly in U.S. dairy herds since the outbreak was detected this spring. More than 600 dairy herds have been infected in 15 states; California – the country’s largest milk producer – has been hit the hardest.

Last month, bird flu was found in at least one pig in a backyard farm in Oregon, the first detection of the H5N1 virus in swine in the United States. That discovery has worried scientists and public health officials because pigs can become co-infected with bird and human viruses, allowing genes to swap to form a new, more dangerous virus that can more easily infect humans.

The Oregon farm also had poultry infected with bird flu, and genetic sequencing has linked the virus to migratory birds, not the version spreading in dairy cows.