California health officials reported Tuesday that a child in Alameda County tested positive for H5 bird flu last week.

The source of infection is not known — although health officials are looking into possible contact with wild birds — and the child is recovering at home with mild upper respiratory symptoms.

Health officials have confirmed the “H5” part of the virus, not the “N1.” There is no human “H5” flu; it is only associated with birds.

The child was treated with antiviral medication, and the sample was sent to the U.S. Centers for Disease Control and Prevention for confirmatory testing.

The initial test showed low levels of the virus and, according to the state health agency, testing four days later showed no virus.

“The more cases we find that have no known exposure make it difficult to prevent additional” infections, said Jennifer Nuzzo, professor of epidemiology and director of the Brown University School of Public Health’s Pandemic Center. “It worries me greatly that this virus is popping up in more and more places and that we keep being surprised by infections in people whom we wouldn’t think would be at high risk of being exposed to the virus.”

A statement from the California Department of Public Health said that none of the child’s family members have the virus, although they, too, had mild respiratory symptoms. They are also being treated with antiviral medication.

The child attended a day care while displaying symptoms. People the child may have had contact with have been notified and are being offered preventative antiviral medication and testing.

“It’s natural for people to be concerned, and we want to reinforce for parents, caregivers and families that based on the information and data we have, we don’t think the child was infectious — and no human-to-human spread of bird flu has been documented in any country for more than 15 years,” said CDPH Director and State Public Health Officer Dr. Tomás Aragón.

The case comes days after the state health agency announced the discovery of six new bird flu cases, all in dairy workers. The total number of confirmed human cases in California is 27. This new case will bring it to 28, if confirmed. This is the first human case in California that is not associated with the dairy industry.

The total number of confirmed human cases in the U.S., including the Alameda County child, now stands at 54. Thirty-one are associated with dairy industry, 21 with the poultry industry, and now two with unknown sources.

In Canada, a teenager is in critical condition with the disease. The source of that child’s infection is also unknown.

Genetic sequencing of the Canadian teenager’s virus shows mutations that may make it more efficient at moving between people. The Canadian virus is also a variant of H5N1 that has been associated with migrating wild birds, not cattle.

Genetic sequencing of the California child’s virus has not been released, so it is unclear if it is of wild bird origin, or the one moving through the state’s dairy herds.

In addition, WastewaterScan — an infectious disease monitoring network led by researchers from Stanford University and Emory University, with laboratory support from Verily, Alphabet Inc.’s life sciences organization — follows 28 wastewater sites in California. All but six have shown detectable amounts of H5 in the last couple of weeks.

There are no monitoring sites in Alameda Co., but positive hits have been found in several Bay Area wastewater districts, including San Francisco, Redwood City, Sunnyvale, San Jose and Napa.

“This just makes the work of protecting people from this virus and preventing it from mutating to cause a pandemic that much harder,” said Nuzzo.

President-elect Donald Trump announced Tuesday he plans to nominate Mehmet Oz, a celebrity heart surgeon and former daytime television host, as administrator for the Centers for Medicare and Medicaid Services.

Oz, a 64-year-old cardiothoracic surgeon, has no experience running a government agency, and has been accused by many U.S. physicians and other health experts of peddling pseudoscience.

If his nomination is approved by the Senate, Oz will head a federal agency that provides health coverage to more than 160 million people and oversees critical programs such as Medicare, Medicaid and the Children’s Health Insurance Program.

“I have known Dr. Oz for many years, and I am confident he will fight to ensure everyone in America receives the best possible Healthcare, so our Country can be Great and Healthy Again!” Trump said in a statement on his Truth Social platform.

Trump said Oz would work closely with Robert F. Kennedy Jr., whom the former president nominated last week to lead the Department of Health and Human Services. Together, Trump said in his statement, the two men would take on “the illness industrial complex, and all the horrible chronic diseases left in its wake.”

“Our broken Healthcare System harms everyday Americans, and crushes our Country’s budget,” Trump said. “Dr. Oz will be a leader in incentivizing Disease Prevention. He will also cut waste and fraud within our Country’s most expensive Government Agency.”

The son of Turkish parents, Oz graduated from Harvard before getting his medical degree and master’s of business at University of Pennsylvania. He went on to serve as a professor of surgery at Columbia University. After rising to fame as a celebrity physician on Oprah Winfrey’s talk show, Oz hosted “The Dr. Oz Show” from 2009 to 2022. In 2008, Time magazine included Oz on its list of “100 Most Influential People.”

But Oz is a controversial figure in the medical world whose television appearances have drawn criticism from fellow physicians who say he backs questionable alternative medicine and unproven weight loss products. In 2012, Oz invited a woman onto his show who claimed she was a psychic and could communicate with the dead. During the COVID-19 pandemic, Oz promoted hydroxychloroquine as a treatment despite a lack of scientific evidence.

At a 2014 congressional hearing, then-Sen. Claire McCaskill (D-Mo.) scolded Oz for his hype of weight loss products. “I don’t get why you have to say this stuff, because you know it’s not true,” she told Oz. “So why — when you have this amazing megaphone and this amazing ability to communicate — why would you cheapen your show by saying things like that?”

After Trump’s announcement Tuesday, many public health experts took to social media to denounce Oz.

Lawrence Gostin, a law professor at Georgetown University who specializes in public health law and directs the World Health Organization’s Center on Global Health Law, said Oz was unfit to lead the Centers for Medicare and Medicaid Services.

“He peddles conspiracy theories on vaccines & fake cures,” Gostin posted. “He profits from fringe medical ideas. By nominating RFK Jr & Mehmet Oz, Trump is giving his middle finger to science. Having worked for 40 years in public health, it’s utterly disheartening.”

“Madness,” wrote Timothy Caulfield, a professor of health law and science policy at the University of Alberta. “Another anti-science quack given power over a science-informed institution.”

In 2022, Oz ran an unsuccessful campaign to represent Pennsylvania in the Senate. Backed by Trump, he cast himself as a moderate Republican who wanted to cut inflation and crime, but he was ultimately defeated by Democrat John Fetterman.

In picking Oz, Trump continues his strategy of nominating unorthodox TV personalities to his administration for his second term.

Last week, he nominated Pete Hegseth, a National Guard veteran and “Fox & Friends” host, as secretary of Defense. On Monday, he nominated former Wisconsin Rep. Sean Duffy, known as co-host of “The Bottom Line” on Fox Business and a onetime reality TV star, to head the Department of Transportation.