H5N1 bird flu has spread across US livestock, infecting 100 million birds and now spreading into both cows and humans, with a virologists warning ‘We are looking at, potentially, a huge outbreak’
The Center for Disease Control (CDC) has confirmed a further three positive human cases in the ongoing H5N1 bird flu outbreak in the United States, which has seen a surge in animal-to-human transmission in recent months as the virus tears through poultry and dairy farms. 10 farm workers have fallen ill since April with the highly contagious virus, which has infected 100 million birds in the US and has now spread to cows as well as humans.
This fresh outbreak in Colorado takes the total number of human cases of H5N1 bird flu this year to 13 with two farms, totalling three million birds, at the centre of the bird-to-human transmissions. Though this is “concerning”, the CDC has said that “all three people have mild illness” and have been offered an antiviral drug, adding that the risk to the general public “remains low”.
However, authorities in the US are now ramping up testing across the state, with milk now under the scope after the virus was found to have spread to more than 170 dairy herds. Virologist Angela Rasmussen, a researcher with the University of Saskatchewan’s Vaccine and Infectious Disease Organization told CBC: “We are looking at, potentially, a huge outbreak that is still expanding, and still growing, and that is not containable.”
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As in the early days of Covid, when a handful of cases in a few countries quickly snowballed into millions of infections, the virologist warned that even a few H5N1 cases are a cause for concern. She said: “That increases the risk of more and more human cases, which in turn increases the risk that this virus will become better adapted to humans.”
Thankfully, none of these human H5N1 infections have shown an ability to transfer between people, but Rasmussen cautioned that continued infections increase the risk of this happening.
As part of measures to tackle the spread of the virus, dairy farmers in the largely rural state were ordered this week to start testing their milk on a weekly basis for traces of bird flu, as the virus starts to spread into other animal populations – now affecting a quarter of Colorado’s cattle herds.
But amid a statewide heatwave that is thought to have contributed to this spike in cases, chicken farms have had to cull flocks en masse. Since the start of July, the Denver Post reports that more than 3.2 million chickens have had to be culled as H5N1 continues to devastate poultry farmers.
The CDC has not changed its advice to the American public on H5N1 following the surge in human cases, which are:
- • People should avoid unprotected exposure to sick or dead animals, including wild birds, poultry, other domesticated birds, and other wild or domesticated animals (including cows).
- • People should also avoid unprotected exposure to animal faeces (poop), bedding (litter), unpasteurized (“raw”) milk, or materials that have been touched by, or close to, birds or other animals with suspected or confirmed A(H5N1) virus.
- • CDC has interim recommendations for prevention, monitoring, and public health investigations of A(H5N1) virus infections in people. CDC also has updated recommendations for worker protection and use of personal protective equipment (PPE). Following these recommendations is central to reducing a person’s risk and containing the overall public health risk.