Rare Bird Flu Outbreak Jumps To Mammals, Killing A Fox And Seals


Rachael Funnell

Social Editor and Staff Writer

clockOct 18 2021, 17:26 UTC
bird flu

All evidence points to a group of swans as the source of the outbreak. Image credit: Shine Crazy /

As COVID-19 continues to spread across the globe, health authorities are understandably fearful of yet another zoonotic disease passing to humans. As such, a recent report about a small but worrying outbreak of bird flu has attracted concern in the UK. The occurrence is a notable one as it spread from birds to mammals, infecting and killing a fox and at least three seals.

The event occurred at an unnamed wildlife rehabilitation in the UK in late 2020 and is detailed in a new paper published in the journal Emerging Infectious Diseases. It began with the arrival of five poorly swans that presented with sudden-onset fatigue and seizures and later tested positive for the avian influenza strain H5N8.


The swan’s deaths were the beginning of an unusual string of fatalities as a fox (Vulpes vulpes), four juvenile common seals (Phoca vitulina), and a juvenile gray seal (Halichoerus grypus) also died or were euthanized with symptoms shortly after. All of the mammals infected presented with severe symptoms including seizures.

The report concludes that all evidence points towards the swans as the source of the outbreak and that the disease spread to other animals also contained within the quarantine facility of the wildlife rehabilitation center. If so, this indicates the disease spread either through aerosols or infected surfaces, as is also the case for COVID-19

“Although the quarantine facility is designed to limit spread of infectious microorganisms through the use of good basic hygiene practices, it is not a biosecure facility designed to handle Biosafety Level 3 pathogens; as such, highly transmissible agents such as avian influenza may well spread even with some infection prevention measures in place,” wrote the authors.


“Because influenza infection was not suspected at the time of the event, biosecurity practices at the center may have been less effective at preventing spread compared with those implemented at a heightened level of biosecurity, which would likely have been in place had there been an awareness of the presence of influenza infection.”

The event is cause for concern in that it’s not often bird flu is able to jump to and incapacitate several mammals. However, despite being catastrophic for the fox and seals, investigations into the strain appear to indicate it’s not a strain of concern for humans.

“Although genetic analyses indicated no increased risk for human infection with the H5N8 viruses in this outbreak, the investigation shows how these viruses may have unexpected and severe health risks for mammalian species,” wrote the authors. “However, such spillover disease events in atypical host species constitute additional factors for veterinary authorities to consider during disease outbreaks and highlight the importance of wildlife disease surveillance that uses interdisciplinary and collaborative approaches.”


The H5N8 bird flu strain made the news earlier this year as it was reported in humans for the first time, having infected poultry plant workers in Russia. Other strains of concern are H5N1, H7N9, and H5N6, as a handful of rare exceptions that can jump from birds to people. These “spillover” events are also uncommon in jumping from birds to mammals, generally speaking, making this infection in foxes and seals one of note.

[H/T: Live Science]

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  • Influenza,

  • bird flu