Bird flu spreads to foxes and otters
Britain is in the midst of the biggest ever outbreak of bird flu and the virus has now spread into mammals, authorities have found.
Avian influenza has killed millions of birds worldwide, both wild and captive, and the UKHSA has reported that four otters and five foxes died after catching the virus.
These animals are known to eat carrion and it is believed the mammals became infected after scavenging on a dead bird which was killed by avian influenza.
Prof Ian Jones, a virologist at the University of Reading, said it “is not too surprising” that some mammals have caught the virus from birds because it is so rampant currently.
However, there is some concern that the virus picked up genetic mutations after getting inside the mammals.
But while some early signals have pricked the ears of scientists, they caution that sustained and widespread infection between mammals, including humans, would require far more significant genetic changes in order to overcome the natural barriers that prevent bird flu from infecting all animals.
The UK is now expanding its mammalian bird flu surveillance to better track any changes to the virus.
However, health officials say there is no evidence that the mammals in the UK are currently passing the virus among themselves and the threat to human health remains low.
One strain of avian influenza, H5N1 22.214.171.124b, is dominant and is driving the current outbreak which is incredibly virulent and deadly in birds.
Previous spillovers of bird flu into mammals have occurred but are rare and only happen when there is a vast amount of bird flu in circulation.
Nine positive cases in mammals
Analysis of 56 mammals by the UK Health Security Agency (UKHSA) and the Animal and Plant Health Agency (APHA) found nine positive cases in mammals.
In Spain last month it emerged that bird flu had infected a mink farm and was passing from mammal-to-mammal, which the UKHSA acknowledged as being “of serious concern”.
Prof Munir Iqbal, head of the Avian Influenza Group at The Pirbright Institute, told The Telegraph: “There is one mutation called PB2 E627K which happened very quickly after the animals became infected and it helps the virus replicate better in mammals.
“But just because it can replicate better does not mean the virus also has the ability to transmit to a new host and make a transmission chain. It is just that, in that infected host, it may help to replicate better.”
“At present, there are no indicators of increasing risk to human health,” the UKHSA said as it expanded its surveillance of mammals and investigation into bird flu.
They warn that because of the sheer amount of birds catching and dying of the virus at the minute that the risk of a human catching it is higher, such instances are still “infrequent”.
Scientists in Spain and at the UKHSA have identified two mutations in the bird flu virus of note related to mammalian infection.
The T271A mutation found in the Spanish mink farm is “uncommon” and “may have public health implications”, the scientists from the Spanish Ministry of Agriculture, Fisheries and Food said.
“Indeed, the same mutation is present in the avian-like PB2 gene of the 2009 pandemic swine-origin influenza A(H1N1) virus.”
The UKHSA warns that the PB2 mutations “may imply this virus has a propensity to cause zoonotic infections”.
But after looking at all the data available, including the mink study, the APHA concludes there is no “widespread mammalian adaptation of this virus”.
Avian influenza is now classed as a level three, on a scale of one to five, which means there is “evidence of viral genomic changes that provide an advantage for mammalian infection” but there is no sustained transmission.