Summary
Report type: immediate notification
Date of start of the event: 21 Nov 2020
Date of confirmation of the event: 26 Jan 2021
Ended on: 12 Feb 2021
Reason for notification: unusual host species
Reported on: 15 Mar 2021
Manifestation of disease: clinical disease
Causal agent: Highly pathogenic avian influenza virus
Serotype: H5N8
Nature of diagnosis: laboratory (advanced)
This event pertains to a defined zone within the country.

New outbreaks (1)
Summary of outbreaks:
Total outbreaks: 1
Outbreak location: Runnymede, Surrey, England
Date of start of the outbreak: 21 Nov 2020
Ended on: 12 Feb 2021
Epidemiological unit: not applied
Affected animals:
Species / Susceptible / Cases / Deaths / Killed and disposed of /
Slaughtered-Killed for commercial use / Vaccinated
Gray seal (_Halichoerus grypus_): Phocidae-Carnivora / - / 1 / 0 / 1 /
0 / 0
Harbor seal (_Phoca vitulina_): Phocidae-Carnivora / - / 4 / 1 / 3 / 0
/ 0
Red fox (_Vulpes vulpes_): Canidae-Carnivora / - / 1 / 1 / 0 / 0 / 0

Epidemiology
Source of the outbreak(s) or origin of infection: contact with wild
species
Epidemiological comments: carcasses of 4 common seals, one grey seal,
and one red fox submitted to APHA [Animal and Plant Health Agency]
laboratory during December 2020 for diagnostic PME [post mortem
examination] as part of routine wildlife disease surveillance
activities. 2 of the common seal carcasses were autolyzed so were
safely disposed of without PME. Following histopathological
examination of tissues from the fox and seals identified lesions
indicative of acute systemic viral infection, further laboratory
testing was performed at APHA. This testing resulted in the detection
of H5N8 influenza virus infection. Gene sequencing identified this
H5N8 influenza virus to be [99.9%] identical to avian-origin H5N8
viruses detected from the mute swans that had died and been tested
from this wildlife rescue centre. In November 2020, 5 wild mute swans
(_Cygnus olor_) that had been rescued and taken to a wildlife rescue
centre died, were tested and found to be infected with H5N8 HPAI.
Retrospective investigation of the deaths of 5 seals -- 4 common seals
(_Phoca vitulina_) and one grey seal (_Halichoerus grypus_) -- and one
red fox (_Vulpes vulpes_) approximately one week later at the same
wildlife rescue centre resulted in the finding of H5N8 influenza virus
infection. These were all wild animals temporarily located at the
wildlife rescue and rehabilitation centre. Comorbidities were not
investigated, and it is possible that other factors may have
influenced disease severity. Infection of mammalian species is a rare
event, with no prior authenticated cases of H5N8 infection in foxes.
All laboratory investigations and testing were performed at APHA. Test
results confirm both the H5N8 influenza virus being of avian origin
and the source hypothesis as the mute swans at the rescue centre that
were also H5N8 positive. There was no evidence of spread of infection
from the wildlife rescue centre.

Control measures applied in wild: official disposal of carcasses,
by-products, and waste; disinfection

Diagnostic test results
Laboratory name and type: Animal and Plant Health Agency (APHA)
Species / Test / Test date / Result
Red fox / Virus isolation / 25 Jan 2021 / Positive
Harbor seal, red fox, gray seal / Gene sequencing / 26 Jan 2021 /
Positive
Harbor seal, red fox, gray seal / Reverse transcription-polymerase
chain reaction (RT-PCR) / 22 Jan 2021 / Positive

Future reporting
The event is continuing. Weekly follow-up reports will be submitted.