The New Yorker:

According to the C.D.C., the risk to public health remains low. But the country’s initial approach has had an unsettling resonance with the first months of COVID.

By Dhruv Khullar 

In December, 2021, a few weeks after the Omicron variant emerged to spark a new, punishing phase of the covid-19 pandemic, Jim Lester’s birds got sick. Lester, who owns an exhibition farm in Newfoundland, Canada, learned that the culprit wasn’t the novel coronavirus but the first known outbreak in North America of a highly pathogenic strain of bird flu, called H5N1. Hundreds of birds were infected and died. Scores more—peacocks, geese, an emu—had to be culled. They all “had personalities,” Lester said. “It was a true tragedy.” Since then, the virus has propagated down through the Americas, killing tens of millions of birds and, perhaps more concerning, infecting dozens of mammalian species: bottlenose dolphins in Florida; sea lions in Peru; elephant seals on the islands near Antarctica. Now, for the first time, the virus is circulating among cattle, and at least thirty-four herds across nine states in this country are known to be infected. Last month, the Food and Drug Administration announced that one in every five samples of milk in the United States carries fragments of the virus, suggesting an even wider spread. One expert called the situation “totally unprecedented.”

Influenza is a promiscuous pathogen. Its potential to unleash pandemics is due partly to the modular structure of its genome, which allows it to swap segments of its genetic material wholesale when different versions of the virus co-infect a cell. This occurred in the mid-nineties, when H5N1 was first isolated, from a goose in southern China, and went on to infect some twenty per cent of the poultry in Hong Kong markets, precipitating the slaughter of more than a million and a half chickens. In the intervening decades, the virus has periodically caused devastating outbreaks in poultry, but it remains poorly suited to the human respiratory tract, and that has limited its spread among people. Still, for those who do get infected—usually farmworkers and others with exposure to animals—the effects can be lethal. In some prior outbreaks, the virus inflicted a case-fatality rate of more than fifty per cent. Fortunately, only two people in the U.S. are known to have been infected, and both experienced mild symptoms. Since 2022, only about two dozen human cases have been recorded worldwide, and, according to the Centers for Disease Control and Prevention, the risk to public health remains low.

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