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A bird-flu pandemic is far from inevitable. But health experts are closely monitoring an outbreak that could quickly escalate among people.
When bird flu first struck dairy cattle a year ago, it seemed possible that it might affect a few isolated herds and disappear as quickly as it had appeared. Instead, the virus has infected more than 900 herds and dozens of people, killing one, and the outbreak shows no signs of abating.
A pandemic is not inevitable even now, more than a dozen experts said in interviews. But a series of developments over the past few weeks indicates that the possibility is no longer remote.
Toothless guidelines, inadequate testing and long delays in releasing data — echoes of the missteps during the Covid-19 pandemic — have squandered opportunities for containing the outbreak, the experts said.
In one example emblematic of the disarray, a few dairy herds in Idaho that were infected in the spring displayed mild symptoms for a second time in the late fall, The New York Times has learned. In mid-January, the Department of Agriculture said that no new infections in Idaho herds had been identified since October. But state officials publicly discussed milder cases in November.
That a second bout of infections would produce milder symptoms in cattle is unsurprising, experts said, and could be welcome news to farmers. But reinfections suggest that the virus, called H5N1, could circulate on farms indefinitely, creating opportunities for it to evolve into a more dangerous form — a “high-risk” scenario, said Louise Moncla, an evolutionary biologist at the University of Pennsylvania.
“You could easily end up with endemically circulating H5 in dairy herds without symptoms, obscuring rapid or easy detection,” Dr. Moncla said.