Concerns are rising about the potential for the H5N1 bird flu virus to cause a pandemic like covid-19. But the situation this time around is very different: we know how to fight influenzas very well, vaccine stockpiles already exist and we have robust flu surveillance systems in place. However, the virus has been infecting people, spreading among animals and mutating – keeping public health officials on high alert.
How concerned should we be?
Of the pathogens with pandemic potential, H5N1 is high on the list, says at Northwestern University in Chicago, Illinois. It is highly infectious, at least in birds, and incredibly lethal to them. More troubling, however, is that H5N1 is remarkably adaptable, says at Johns Hopkins University in Maryland. It has jumped into dozens of mammal species, including house cats, and since March 2024, it has affected cows in more than .
However, because H5N1 hasn’t been found to transmit between people, the risk to the general public remains low – although it is higher for dairy and poultry workers. “If we start to see changes in the virus, including changes that might make it more severe or more capable of human-to-human transmission, that’s when people should become really concerned about the pandemic potential,” says Davis. For now, caution – or even concern – is warranted, but it isn’t inevitable that H5N1 becomes the next covid-19. People should be worried, if only to be more prepared, says Murphy.
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How dangerous is H5N1 to people?
Since 2003, more than 950 people have reportedly had the virus, about half of whom have died. However, the mortality rate has been lower in the recent US outbreak. In 2024, 66 people in the country tested positive for the virus, and seven others are presumed to have had it. One person in Louisiana died from H5N1, which they contracted from infected chickens or wild birds in their backyard. They were already at high risk because they were older than 65 and had underlying health conditions, so while their death is tragic, it doesn’t change the wider risk assessment.
Are there any signs H5N1 has mutated?
Each time H5N1 infects a mammal, it has a chance to develop mutations that could allow it to transmit between humans. “If this thing mutates a little bit more in the wrong direction, it’s either going to be more severe, kill more people or spread easier, or a combination,” says Murphy. There are already worrying signs of this.
at the Pirbright Institute in the UK and his colleagues found that the virus circulating in US cattle has in mammalian cells. And of samples collected from the person in Louisiana identified several changes that may improve the virus’s ability to bind to influenza receptors more commonly found in humans than birds. One of these changes was also seen in a who fell severely ill with H5N1 but has since .
Another concern is someone catching both H5N1 and seasonal influenza at the same time, allowing the pathogens to swap genetic material. This is why the CDC is recommending people who work in close proximity to animals, such as cows or birds, get the seasonal flu shot, says Murphy.
Are there vaccines for H5N1?
The US Food and Drug Administration has approved for H5N1. However, they aren’t available to the public. They are instead in the country’s vaccine stockpile, in case of a pandemic.
There are roughly 5 million H5N1 vaccine doses ready to be administered, says a spokesperson for the US Administration for Strategic Preparedness and Response (ASPR), and they plan to to 10 million doses. With enough funding, “ASPR could work with manufacturers to deploy more than 100 million doses within months”, says the spokesperson.
Pharmaceutical company Moderna is also using the same mRNA technology that covid-19 vaccines rely on. US company Hologic, which developed some of the covid-19 rapid tests, has also entered into an agreement with the US Centers for Disease Control and Prevention (CDC) to develop such a test for bird flu.
How prepared are we for a bird flu pandemic?
We are in a much better position for H5N1 than we were at the start of the covid-19 pandemic, which caught public health agencies off guard, says Murphy. Not only does the US have stockpiled vaccines, but it also has a robust influenza surveillance system in place to detect significant upticks in H5N1. On 3 January, the US Department of Health and Human Services announced of funding towards efforts like manufacturing tests, stockpiling medical equipment and monitoring dairy and poultry workers.
“But that’s like a drop in the bucket,” says Murphy, noting that much more is needed for the US to truly be ready for a potential pandemic.
