From the middle of Texas to the far reaches of Maine, a highly pathogenic bird flu virus is sweeping through the US.
Over 24 million chickens, turkeys, and farm animals in the US have been killed, culled, or affected in the US as a result of this season’s bird flu outbreak, according to the latest statistics posted by the US Centers for Disease Control and Prevention on April 11. Broken down, it's a total of 159 outbreaks in 25 different states and 98 counties.
Worryingly, the disease outbreak has also seen 637 infected wild birds in 31 different states. Discovering the virus in wild birds is particularly worrying as they can migrate from state to state, seeding the disease as they go.
The virus in question is highly pathogenic avian influenza H5N1. Avian-origin influenza viruses – often known as bird flu – are broadly categorized based on a combination of two groups of proteins on the surface of the influenza A virus: hemagglutinin or “H” proteins, of which there are 16 (H1-H16), and neuraminidase or “N” proteins, of which there are 9 (N1-N9).
Of the many subtypes, two are especially of concern: H5N1 and H7N9. One of the most worrying features of H5N1 infections in humans is its high mortality rate, which is strikingly pronounced in younger people.
With that said, the risk to public health from this outbreak is low, according to the CDC. No human illnesses have been associated with this virus outbreak in North America yet, unlike previous H5N1 outbreaks elsewhere. A human case was reported in the UK earlier this year, but further transmission was contained. Furthermore, no sustained human-to-human transmission has ever been identified.
People shouldn't be too worried about eating poultry or eggs either, but the CDC reminds people to ensure the products are safely handled and cooked. Unfortunately, it will likely result in a noticeable rise in egg prices. Likewise, you should avoid touching wild birds and take extra precautions with avian pets that spend time outside. The outbreak has even forced some zoos to hide away their birds, like penguins and flamingos, out of fear they may also contract the virus.
The US isn’t alone with this problem. Canada, Europe, Africa, the Middle East, and Asia have all been grappling with H5N1 since the autumn of 2020, with the virus becoming the predominant subtype globally by the autumn of 2021.
A number of outbreaks of H5N1 bird flu have occurred in recent decades, some eventually spreading to humans in relatively low numbers. For now, it appears that the H5N1 strain in circulation hasn’t picked up too many red flag mutations that would deeply alert scientists, says the CDC.
“CDC has been comparing the properties of current H5N1 bird flu viruses to past H5N1 bird flu viruses and has found that current H5N1 bird flu viruses detected in the U.S. during late 2021 and 2022 are different from earlier H5N1 bird flu viruses,” said the US health authority. “So far, current H5N1 bird flu viruses lack changes seen in the past that have been associated with viruses spreading easily among poultry, infecting people more easily, and causing severe illness in people.”
Once again, the wider threat on human health is said to be low at the moment. Nevertheless, it has previously been feared that H5N1 is a likely candidate for the next big pandemic, so this latest outbreak is no doubt giving many public health experts some anxiety.
“We're concerned with any avian influenza virus that's circulating in domestic poultry or wild birds. Because humans have no prior immunity to these viruses typically, if they were to be infected and spread the virus to other humans, then we could have another pandemic virus on our hands." Todd Davis, an expert on animal-to-human diseases at the CDC, told NPR.