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APHA provides science evidence quickly leading to the first detection of bird ‘flu in the United Kingdom

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Image of a brown hen standing in a field with other hens in the background.
The arrival of bird 'flu is linked to wild bird migration in the autumn and winter

"The APHA science and field service capabilities are critical in supporting Defra and the Devolved Administrations in preventing, detecting and controlling disease. Our current response is focused on timely activity to manage high levels of disease threat to UK keepers of birds from highly pathogenic avian influenza (HPAI).

We are providing a round the clock operation to ensure successful outcomes. The current response has been underpinned by: key APHA international activities which first detected the threat across Central Asia and the Middle East from newly emerged strains of HPAI; assuring the UK had the best and most reliable diagnostic tests; rapid systems for investigating and sampling reported disease suspicions in poultry; upscaling surveillance in wild birds for the viruses; providing rapid test results to enable timely disease confirmation and imposition of control measures; conducting detailed epidemiological investigations to ensure the disease does not spread.

We are faced with unprecedented events even in the context of avian influenza. Over 230 wild birds tested positive for H5 HPAI (and rising daily), a total 10 disease confirmations in both poultry and captive birds and three different virus serotypes of HPAI, H5N8, H5N5 and H5N1 involved in wild bird cases across England, Wales, Scotland and Northern Ireland. The first occasion the UK has been challenged with this complexity and number of events over a 2 month period and all in the early part of the winter!"

Professor Ian Brown, Acting Deputy Director of Science, APHA

Again, the United Kingdom (UK) and many of our neighbouring and more far flung countries find ourselves in the grip of bird ’flu. This year has seen the arrival of Highly Pathogenic H5N8 Avian Influenza Virus (HPAIV) with disease emerging in both wild birds and poultry. Its arrival is linked to wild bird migration in the autumn and winter with the peak risk being in January and February. In previous years the H5N8 (2014, 2016-17) and H5N6 (2017 and 2018) viruses arrived in the UK in wild birds in mid-December (Christmas party time) and the former was transmitted into poultry, whilst the latter was not.

This year the H5N8-20 virus strain was first detected at the beginning of November and is infecting both wild birds and poultry on small holdings and commercial production units. This has come at a challenging time for our scientists, who are also supporting Public Health England and Defra and Devolved Administrations with additional activities on COVID-19 testing and SARS-CoV-2 applied research.

Image of a map of Europe indicating incidents of Avian influenza in poultry and captive bird species and wild birds. Clusters can be seen across Scandinavia and some in the UK
Avian influenza events in Europe, from the period 27 October to 28 November 2020

The viruses detected in previous years, while the same or similar subtypes (H5N8 or H5N6) are related, whereas this year’s virus is more of a distant cousin as the viruses can swap parts of their genome and as such change their characteristics.

Image of a bar graph with number of events on the y axis and dates on the x axis. The highest number of events appears on 06.11.2020 with the most instances in wild birds and then gradually declines.
European detections of HPAI H5 in poultry, captive birds and wild birds. Sampling dates from 16th October 2020 to 28th November 2020

What do we do to look for disease presence?

APHA works all year around to carry out surveillance for notifiable diseases. For avian influenza, we carry out a number of activities to monitor the international disease situation, as well as sampling and testing both wild birds and the farmed bird population.

The ‘found dead wild bird surveillance scheme’ targets sampling and testing to susceptible wild-fowl species. Wild bird carcases are collected and delivered to our network of Veterinary Investigation centres where they are examined and sampled by our Veterinary Investigation officers (VIOs). As well as testing for presence of avian influenza virus, we also look for West Nile virus, and can investigate other diagnoses if our VIOs find anything of concern that needs further investigation.

We also conduct an annual poultry survey where we visit selected holdings to sample birds for screening for avian influenza virus exposure (antibodies). APHA service delivery teams undertake the farm visits and sampling of birds. Samples are then sent to our Weybridge laboratories for testing.

As with all notifiable diseases, there is a requirement for vets to report suspicion of disease to APHA, these ‘report cases’ are investigated by Service Delivery vets who visit the farm, examine the birds for clinical disease, and take samples (virus and antibodies) for testing if disease cannot be negated on the clinical evaluation alone.

All of this work provides information to inform the disease risk level in the country, for both farmed and wild birds. This in turn reflects any further action that industry and other poultry keepers need to take to protect their livestock, and any plans APHA may need to take to increase surveillance activities, and also the containment level of laboratory we safely and securely handle samples in.

What happens when we detect disease?

There are two ways that disease past or present can be detected.

Firstly, via routine screening where there is no disease in the flock and secondly, by clinical disease seen by bird keepers and/or their veterinarians – a disease suspicion or report case (below).

If we detect prior exposure to infection during routine screening of samples (blood/antibodies), we call these non-negative. Further investigation is done to determine if there is ongoing active infection in the sampled birds by collecting swabs and testing for virus using molecular methods (PCR tests). We also do virus isolation by propagating the virus to determine if live (transmissible) virus is present.

Samples from diseased birds are tested rapidly by PCR and within a few hours of receipt we are able to detect very small quantities of the genetic material of the virus if infection is present. Any viruses detected are deeply characterised by genome sequencing to determine many traits both biological (i.e. pathogenicity) and genetic to include understanding of where the virus came from and the relationship to those from other outbreaks both nationally and internationally. In addition we determine the risk for onward infection of a wide range of hosts including humans.

Image of a common Buzzard.
So far this year the H5N8 strain has been detected in poultry (chickens, ducks and mixed species) and wild birds; goose breeds mainly (Canada and Greylag in the UK, Barnacle and others across Europe) and also some swan species, gull species and birds of prey like Buzzard, as shown above.

How do we control an outbreak?

As soon as we have a case of disease suspicion because birds are showing clinical disease that may be an indicator of virus infection, or a non-negative test result from routine surveillance testing of farmed birds, the Veterinary Exotic Notifiable Disease Unit (VENDU) instruct the APHA service delivery teams to put in place restrictions on the premises. This ensures that no birds or products are moved off the premises, and introduces biosecurity measures to prevent disease being spread.

Once initial testing gives confirmation of disease presence and information for the type of virus present, this, along with our wider knowledge of disease risk, allows the Chief Veterinary Officer (CVO) to make decisions about what further actions are required. If the risk level is high, which is always the case when highly pathogenic avian influenza is present, the decision will be made to cull birds on the infected premises upon suspicion of disease. This is a proven methodology to stop the spread of this very dangerous disease and thereby protect other birds from serious welfare effects including death.

Asking questions about virus survival in the environment, disinfection, infectivity, pathogenesis and transmission within and across species, sequence analyses comparing evolution from other recent strains (H5N8, H5N5, H5N1, H5N6 etc.) and impact of prior H5 virus infection induced immunity help Defra and the CVOs to manage, mitigate and eliminate this disease and return UK trade back to business as usual as quickly as possible whilst importantly protecting the health and welfare of birds and other animals.

Confirmation of disease also triggers the mobilisation of the National Emergency Epidemiology Group (NEEG). This team is formed of analytical and field epidemiologists, modellers, data scientists, risk analysts and project managers. They work on the epidemiological investigation within an outbreak, informing on likely source and spread of the disease, producing a sampling strategy and providing advice to policy teams in the National Disease Control Centre (NDCC) to enable them to make further decisions. These decisions need to be timely to control the risk of spread of disease. A protection zone around the infected premises (IP) is put in place, as well as a surveillance zone around a wider area.

A veterinary field epidemiologist will be deployed to carry out a detailed on-site epidemiological investigation. Work then begins to obtain information on recent movements onto and off of the IP. These tracings are followed up to look for presence of disease elsewhere. Data scientists within the NEEG use information on registered poultry keepers to identify holdings in the zones, and foot patrols are undertaken to look for other poultry that may be present, such as small unregistered flocks.

Surveillance activities are undertaken to check for spread of infection including specifically inside the zones. Tracing visits with inspections and record checks are forms of surveillance within and outside the zones. Sampling may be conducted if required. Any movements of livestock in these zones has to be licenced and controlled to prevent risk of disease spread, whilst also ensuring that welfare of livestock is managed. In addition, owners and other operatives are supported through public health systems to ensure no risk of infection from infected birds.

Once all surveillance testing has concluded satisfactorily then the restrictions and zones can be lifted (typically at 30 days after the first disinfection of the IP). The NEEG produce an epidemiological report on each outbreak which is published on GOV.UK.

Bar graph with number of detections on the y axis and dates along the x axis. Lower incidents shown until small peaks shown in 1959-63 (HPAIV), 1974-78 (LPAIV), 1979-83 (HPAIV and LPAIV), 2004-08 (HPAIV, LPAIV and wild birds events) 2014-16 (HPAIV, LPAIV, wild birds events and non-H5/H7), 2018 (LPAIV and wild birds events), 2019 (LPAIV and non-H5/H7) and the biggest peak in 2020 (HPAIV, LPAIV, wild birds events and non-H5-H7).
Graph to show the number of bird flu notifiable detections (H5/H7) in the United Kingdom between 1959 to the end of November 2020. HPAIV = highly pathogenic, LPAIV = low pathogenicity avian influenza virus


Protecting our livestock from notifiable diseases like avian influenza, and supporting industry and UK trade by providing official disease freedom status requires APHA to work across multiple disciplines to understand disease risk, ensure we can detect disease presence, and when we do, act fast to control the spread.

Understanding the risks from wild birds and sharing information and advice with poultry keepers helps protect our commercial and other birds whilst controlling outbreaks.

APHA’s remit extends beyond livestock diseases and you can be assured that our teams are ready to respond to a range of animal, plant and bee health threats 365 days a year!

How you can help

Do not touch or pick up any dead or visibly sick birds that you find.

If you find dead wild waterfowl (swans, geese or ducks) or other dead wild birds, such as gulls or birds of prey, you should report them to the Defra helpline (03459 33 55 77).

If you keep poultry or game birds, you have a legal requirement to register to the Poultry register if you keep more than 50 birds. You can also voluntarily register if you have less than this number to receive alerts of any disease risks in your area.

If your poultry or other captive birds are sick or die contact a veterinarian.

Further guidance and updates on the current avian influenza situation are also posted regularly on

Further reading on avian influenza

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