Bird Flu in US Cows: WHO Warns 'Extremely High' Mortality Rate in Humans As H5N1 Spreads to Milk

Bird Flu, also known as H5N1, has spread in cattle across the United States over the last month. The spreading of highly pathogenic avian influenza has sparked concern among health experts, including the World Health Organization's (WHO) chief scientist, who warned of the virus' "extremely high" mortality rate in humans.

According to a report by BBC Science Focus, avian influenza has infected more than 20 cattle herds across 8 US states, including Idaho, Kansas, Michigan, New Mexico, North Carolina, Ohio, Texas, and South Dakota, since it was first reported to have made the jump in March 2024.

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Earlier in April, the Centers for Disease Control and Prevention (CDC) stated that the virus had spread in Texas and infected a human who had been exposed to dairy cattle.

“On an individual level, there’s no immediate cause for concern. From a public health standpoint, however, there is an extremely high level of concern,” said Dr. Jeremy Rossman, an honorary senior lecturer in virology at the University of Kent, to BBC Science Focus.

“Extreme vigilance, research, and assessment of the situation are needed because that risk scenario for an individual person could change very rapidly,” Rossman added.

H5N1 was first detected in 1996 when it was found in domestic waterfowl in China. A new version of the virus gained attention in 2021 and has since gone on to infect wild and domestic birds worldwide. Millions of birds have been culled globally, including in India.

After the virus spread among birds, it has also affected other animals. According to the CDC, the list of mammals affected includes foxes, seals, sea lions, and humans.

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According to the WHO, of the 868 human cases detected between 2003 and 2022, over 50 per cent resulted in death – but, as Rossman explains, it’s usually short-lived. Now, the US Department of Agriculture (USDA) has confirmed that not only have cows been infected for the first time, but also that cow-to-cow transmission is a factor in the recent bird flu spread on dairy farms.

“We know that the virus is shed in milk at high concentrations; therefore, anything that comes in contact with unpasteurized milk, spilled milk, etc. may spread the virus,” said USDA.