Does the spread of bird flu to mammals mean a greater risk to humans?

Avian flu is an infectious type of influenza that spreads among birds.
Avian flu is an infectious type of influenza that spreads among birds. Avian flu is an infectious type of influenza that spreads among birds.

Some otters and foxes in the UK have been infected with bird flu, with experts suggesting they may have eaten dead wild birds that carried the virus.

But does this mean avian flu can be passed to humans and other mammals, and what is the risk of this happening?

PA media answers some of the main questions.

– What is bird flu?

Bird flu, or avian flu, is an infectious type of influenza that spreads among birds. In rare cases, it can affect humans.

There are lots of different strains of bird flu virus, and most of them do not infect humans.

More than seven million captive birds have died of bird flu or been culled for disease control since an outbreak started in October 2021.

There have been 279 cases of H5N1, avian influenza, in England since the outbreak started, according to figures released last month by the Department for Environment, Food and Rural Affairs (Defra).

– What has actually happened to raise concerns about spread to mammals?

The UK Health Security Agency (UKHSA) reported in December that 20 mammals had been tested in the UK, of which eight (foxes and otters) were positive for avian flu.

Since then, this figure has been updated to nine.

– How could mammals have become infected with bird flu?

The species affected – foxes and otters – are known to scavenge.

In all likelihood, the affected animals will have scavenged infected wild bird carcasses, which may have had very high levels of the virus.

Such high exposure is likely to have overwhelmed the mammal’s immune system, resulting in infection.

– Now that foxes and otters have been infected, does this mean there’s a risk to people? 

Experts and officials say the risk to humans remains low.

Dr Alastair Ward, associate professor of biodiversity and ecosystem management, at the University of Leeds, says that while the developments do not increase the risk of the virus spilling over into humans, this is not 100% certain.

He explained: “Humans rarely come into contact with wild foxes or otters, and potentially infectious contact is likely to be rarer still.

“In the past, a relatively small number of humans who have lived or worked very closely with affected poultry e.g. in slaughter houses, have become infected with highly pathogenic avian influenza, with variable outcomes.”

While there is no transmission within mammalian populations, the risk to humans remains low.

Experts say sensible precautions can be taken like avoiding contact with wild mammals and birds, wearing protective gloves and a face covering if contact is unavoidable, and washing hands and soiled clothing with soap and water after exposure to affected environments.

– Do the latest developments mean the virus is mutating? 

Experts say there is currently no reason to suspect the jump is due to a change in the virus’s genetic make-up.

However, experts say the cases in otters and foxes illustrate a potential risk we need to be vigilant about.

But Professor Ian Jones, a virologist at the University of Reading, suggests the risk to people right now appears no more than it is for direct spread from infected birds.

– Should we be concerned about the spread to other animals?

Symptoms in mammals can vary considerably, but in the past there has been no mass death of these animals that may get infected with bird flu.

While finding the virus in wild mammals in the UK is of concern, there is currently no reason to expect that it will spread through wild mammal populations.