Avian flu surveillance is being ramped up in the UK after the detection of at least 200 cases of infection in mammals.
Public health experts say the risk of a jump to humans is still very low, but that this risk would be monitored through increased genomic surveillance and targeted testing of people who had been exposed to the virus. Concern was also sparked by a recent outbreak of avian flu at a mink farm in Spain and a mass mortality of seals in the Caspian sea that is possibly linked to the infection.
“The virus is absolutely on the march,” Prof Ian Brown, the director of scientific services at the Animal and Plant Health Agency (Apha), told the BBC.
He added that experts were “acutely aware of the risks” of avian flu becoming a pandemic like Covid. “This global spread is a concern,” he said. “We do need globally to look at new strategies, those international partnerships, to get on top of this disease.”
Over the last two years, the UK has faced its largest outbreak of avian influenza, with more than 300 cases confirmed since October 2021 and with poultry farms all currently required to house birds indoors.
Figures reported by the BBC show the virus has led to the deaths of about 208 million birds around the world and at least 200 recorded cases in mammals. In the UK, Apha has tested 66 mammals, including seals, and found nine otters and foxes were positive for highly pathogenic avian influenza (HPAI) H5N1.
Such cases have been found in Durham, Cheshire and Cornwall in England; Powys in Wales; Shetland, the Inner Hebrides and Fife, Scotland. It is believed the animals had fed on dead or sick wild birds infected with the virus.
“The species affected – foxes and otters – are known to scavenge,” said Dr Alastair Ward, of the University of Leeds. “In all likelihood, the affected individuals will have scavenged infected wild bird carcasses, which may have had very high viral loads. Such high exposure is likely to have overwhelmed the mammal’s immune system, resulting in infection.”
There is currently no reason to suspect that the jump is due to a change in the virus’s genetic makeup or that the risk to humans is greater from infected foxes or otters than from birds. However, scientists believe close monitoring is required to detect any mutations that could make a leap between species more likely. And reports of the apparent spread of the virus between mammals on a mink farm and the possibility of an outbreak in the wild seal population have heightened concern.
Prof Ian Jones, a virologist at the University of Reading, said: “While these constant incursions of the virus into mammalian species does provide an opportunity for the virus to adapt to mammalian transmission, the natural barriers to this occurring are quite high and there is no indication of spread within these species. The risk to people right now therefore appears no more than it is for direct spread from infected birds.”
In a recent report, the UK Health Security Agency (UKHSA) warned that the “rapid and consistent acquisition of the mutation in mammals may imply this virus has a propensity to cause zoonotic infections”, meaning it could jump to humans.
The agency also raised concerns about limited wild bird and mammal surveillance and genomic data collection in England, and warned that there was not enough testing of people who had been contact with infected birds.
According to the World Health Organization (WHO) there have been almost 870 cases of human infection in the past 20 years and of these, 457 cases were fatal.
