Possible H5N1 bird flu case in California child; source of infection unknown

Susanne Rust, Los Angeles Times on Dec 7, 2024

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LOS ANGELES — Health officials in Marin County are investigating a possible H5N1 bird flu case in a child.

Officials have been investigating since last week and are working with the California Department of Public Health an the Centers for Disease Control to determine how the child was exposed.

The information was provided in a Dec.6 "health status update" newsletter, and buried at the end of a paragraph about the county and state's monitoring of the virus, raw milk and a note about a new USDA program designed to test milk nationwide.

If confirmed, this would be the second case of an infected child in California.

"It's deeply concerning that another child may have H5N1. We need to know much more about this case, including some hypotheses for how she or he may have contracted the virus," said Jennifer Nuzzo, director of the Pandemic Center at Brown University in Providence, Rhode Island. "Given the proximity of this case to the last case of H5N1 diagnosed in a child without known exposure to animals, it may be prudent to conduct a broader investigation, including a serologic study, to see if there is evidence of other infections in the area."

Last month, state health officials announced a child in Alameda County was positive for the disease. Investigators have not been able to determine the source of exposure. The child suffered from mild respiratory symptoms, and no one else in the child's family or day care was infected.

Neither the state nor county public health officials have responded to queries from the Times, and no further information was provided in the newsletter.

If confirmed, this would be 61st human case of bird flu, this year. Two cases were announced in Arizona Friday — both cases involving dairy workers.

This would also be the third case in the U.S. this year where the source of exposure is unknown. Aside from the case of the child in Alameda Co,, a person in Missouri was also infected by an unknown source.

Outside the U.S., a teenager in Canada was also infected by the virus — source unknown — and has remained in critical condition for three weeks with severe disease.

Most of the human cases in the United States have involved dairy workers and poultry workers — exposed in places where the virus is known to present.

To date, most cases of H5N1 bird flu in people have been mild, involving conjunctivitis, or pink eye, and mild upper respiratory symptoms.

Investigators will need to evaluate the genetic sequencing of the virus to determine if the virus is of dairy or bird origin.

Wastewater samples collected by WastewaterScan — an infectious disease monitoring network led by researchers at Stanford and Emory University, with lab testing partner Verily, Alphabet Inc.'s life sciences organization — has shown virus is widely present in the environment, including Marin Co. sites in San Raphael and Novato.

In the two weeks, state health and agriculture officials suspended and recalled infected raw milk that had made its way to grocery store shelves throughout the state.

There have been no known outbreaks associated with that raw milk, and it is unclear if people can get the disease by consuming it in milk.

However, several mammal species have displayed severe illness and death after consuming raw milk including cats and mice.

Mark McAfee, the owner of the infected raw milk farm — Raw Farm LLC — told the Times last week that he believed the milk had gone out to 90,000 customers.

Asked how he determined that number, he said "Our consumers buy every week.... its very reliable. We have 500 stores and based on dollar volume per check-out its our best guess."

The state's health and agriculture departments were unable to confirm that number.