San Francisco Zoo Closes Aviaries After Bird Flu Is Found in Dead Wild Hawk

The San Francisco Zoo has temporarily closed its indoor bird exhibits after a dead hawk found on its grounds tested positive for bird flu.

The red-shouldered hawk that died was a wild bird that lived on the grounds, and none of the zoo’s birds have tested positive for the disease so far.

“Out of an abundance of caution, we have closed walk-through aviaries to protect the birds and are following biosecurity protocols to minimize the risk of transmission,” the zoo said in a statement posted to social media on Tuesday.

The “extra precautionary measures” apply to indoor exhibit areas such as the African Aviary and South American Tropical Rainforest & Aviary, according to the zoo.

Zookeepers have moved as many birds inside as possible and are doing everything they can to protect the ones that have to stay outside, such as penguins, said Dr. Adrian Mutlow, the zoo’s chief veterinarian.

“Our collection birds are considered at risk because there’s obviously infection on site … so we have to try and take as many precautions as we can to stop the infection getting into our collection,” he said.

The biggest risk, Mutlow said, is posed by infected ducks flying into the zoo grounds since waterfowl are a typical carrier of the disease. Another concern was zoo visitors carrying the virus into the indoor bird exhibits on their shoes or clothes, especially if they have birds at home.

The dead hawk was found last month, and the zoo closed its aviaries as soon as preliminary results came back positive for avian influenza, Mutlow said. About a week later, he said, further testing confirmed it was the highly pathogenic strain — H5N1 bird flu.

Mutlow said he expects the aviaries to reopen in about a month once bird migration season is over.

“We have sort of less extreme measures when we know there are cases in other parts of the state but not close to us at the time,” he said. “But unfortunately, this is as close as it gets. So we have to take the more drastic measures.”

Because of the heightened bird flu risk, the zoo has been routinely testing for the virus, Mutlow said.

San Francisco joins a handful of zoos around the country to take similar safety measures in recent weeks, including the Honolulu Zoo and Seattle’s Woodland Park Zoo, where a rare red-breasted goose died of the disease last month.

Bird flu, also known as highly pathogenic avian influenza, is highly contagious and deadly for poultry species, with mortality rates of 90% to 100% in chickens, often within 48 hours, according to the Centers for Disease Control and Prevention.

The H5N1 bird flu virus has also infected an increasing number of cattle across the country, but it has not yet evolved to efficiently spread between humans, researchers previously told KQED. Public health officials have said the risk to the public is low.

So far this year, there have been 58 recorded bird flu infections in people in the U.S., with most previous cases linked to dairy and poultry workers. The virus can spread from sick cows or birds to people who breathe in droplets of the virus, handle dead animals, drink raw milk or have it splashed on their faces.

A potential case in a child in Marin County, who has since recovered, is among 10 reports of illness state officials have received from people who consumed raw milk. Additional testing is underway to confirm or rule out whether the influenza case was bird flu.

Last month, a child in Alameda County was diagnosed with bird flu without a clear exposure pathway. That case, which resulted in mild respiratory symptoms, did not spread inside the family or at school. This follows the trend in other human bird flu cases where patients presented mild symptoms — primarily conjunctivitis and nasal stuffiness.

KQED’s Lesley McClurg contributed to this report.