Bird Flu Spreads to Dairy Cattle, Farm Worker Infected, Virus Fragments in Milk
Image: NIAID
The bird flu has spread to cattle in the United States. Inactive fragments of the virus have been found in milk. The World Health Organization rates the current risk for humans as low but epidemiologists all over the world are on high alert. I have the summary.
The avian influenza, commonly known as bird flu, comes in many strains. The strain of the current outbreak is H5N1. It was first isolated in farmed geese in China in 1996. Wild birds have since spread all over the world. Among birds, it has a fatality rate exceeding 90% within 48 hours. That’s bad for the birds, but good for us, because it means that outbreaks are discovered very quickly, and contaminated poultry is very unlikely to enter the food chain.
The variant that currently concerns researchers has the number 2.3.4.4b, just so you’ve seen it in case someone asks you on the street tomorrow. This variant was first documented in October 2020 in the Netherlands. Within a few months it had spread across Europe, and to Africa, Asia, and America.
In recent years there have been numerous reports that this variant has infected mammals, including otters, foxes, bears, minks, cats, and now cattle herds in the United States. This new outbreak began in March. By last week, the virus had spread to more than 36 herds in eight states. Genetic analysis suggests the outbreak likely originated from a single spillover event from birds, and the virus then spread between cattle herds.
The cows largely recover after a few weeks, but this is bad news. The H5N1 virus is known to be able to also infect humans. The World Health Organization has counted about 900 cases of infected humans from 2003 to 2024. About half of the infected people died.
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