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Avian influenza, commonly known as bird flu, refers to a variety of influenza type A viruses found in wild and domesticated birds. Since the first outbreaks of bird flu in China and Hong Kong in 1997, the virus has spread worldwide and caused a series of outbreaks, most notably in 2003–05, 2014–16 and 2018–21. These outbreaks resulted in the death of over 410 million birds, causing disruption to agriculture and trade. According to a World Health Organization report published on 4 November 2022, between 2003 (when the virus was first detected outside China) and 21 October 2022, there have been 868 cases of human infection with the avian influenza A(H5N1) virus. Of these 868 cases, 456 were fatal.

Since 2021, the UK has experienced its worst bird flu outbreak. In September 2022, the director of policy at the Royal Society for the Protection of Birds, Jeff Knott, said:

The severity of the situation and scale of the impact is unprecedented and very, very scary. It’s a huge crisis that could turn into a catastrophe unless we get ahead of it.

On 31 October 2022, Dr Christine Middlemiss, the UK’s chief veterinary officer, said:

We are now facing, this year, the largest ever outbreak of bird flu and are seeing rapid escalation in the number of cases on commercial farms and in backyard birds across England.

1. Virus characteristics

Bird flu viruses are classified into two broad categories, based on how pathogenic (disease causing) they are: ‘low pathogenicity avian influenza’ and ‘high pathogenicity avian influenza’. Most bird flu viruses are low pathogenic. In wild birds they cause few, if any, symptoms. In domesticated birds the symptoms are typically mild, including ruffled feathers and decreased egg production. High pathogenic bird flu is severe, lethal and highly contagious, with strains able to kill 90–100% of a flock within 48 hours. In poultry, some low pathogenic bird flu strains can mutate into high pathogenic strains.

2. Bird flu in birds

In wild aquatic birds, bird flu occurs naturally, with the virus being identified in more than 100 wild bird species worldwide. Infected birds shed the virus in their faeces or bodily fluids from their nostrils, mouth and eyes. Although the virus can spread through airborne secretions, the disease itself is not an airborne disease. It is spread from infected to healthy birds by direct contact or, more rarely, by contact with contaminated surfaces.

The most conspicuous sign of bird flu in poultry is rapid increase in the number of birds found dead. Other symptoms include a swollen head, blue/purple colouration in several body parts, dullness, inactivity and lack of appetite, respiratory distress and a significant drop in egg production. Some species, such as ducks, geese and swans, can show minimal clinical signs of infection.

3. Bird flu in humans

Human infections of bird flu are typically acquired through direct contact with infected animals or sustained exposure to contaminated environments. Human-to-human transmission is very rare, as the viruses have not acquired the ability for sustained transmission among humans. However, researchers have warned of the potential for some strains of bird flu to mutate and become transmissible among humans. According to the UK Health and Security Agency, the public health risk of bird flu for humans is “very low”. The Food Standards Agency has stated that bird flu poses a very low food safety risk for UK consumers, as properly cooked poultry and poultry products are safe to eat.

In patients infected with bird flu the severity of the disease can vary. For avian influenza A(H7N7) and A(H9N2) infections the symptoms are typically mild, with very few human fatalities recorded. For avian influenza A(H5) or A(H7N9) infections, the disease can be aggressive. Initial symptoms include upper respiratory infections, such as high fever and cold, and later lower respiratory infections, such as difficulty breathing. Complications can include severe pneumonia, acute respiratory distress syndrome, secondary bacterial and fungal infections, shock and even death. The case fatality rate among humans for these strains of bird flu is much higher than that of seasonal flu infections.

4. Prevalence in 2021–22

The European Centre for Disease Prevention and Control stated that the 2021–22 bird flu epidemic (ranging from October 2021 to September 2022) was “the largest observed in Europe so far”. Over 2,467 outbreaks were reported in poultry and 48 million birds were culled in affected areas across 37 European countries. The Guardian reported that the number of cases in domesticated birds in June–September 2022 was five times higher compared with the same period in 2021. In an interview with the Financial Times in November 2022, Richard Griffiths, the chief executive of the British Poultry Council, stated that the UK has lost 40% of its free-range turkey flock.

As of 9 November 2022, there have been 234 cases of high pathogenic bird flu in England since October 2021. The number of cases has significantly increased in recent months. In October 2022, there were 82 cases in England (four in Scotland, four in Wales and one in Northern Ireland), with 18 more being reported in the first week of November, amounting to 100 total cases from 1 October 2022 to 9 November 2022.

The Department for Environment, Food and Rural Affairs (DEFRA) and the Animal and Plant Health Agency publish regular reports on bird flu outbreaks. In the latest report, published on 24 October 2022, the risk rate for wild birds was set at ‘very high’, the risk for poultry with suboptimal biosecurity at ‘high’ and with stringent biosecurity at ‘medium’. The report stated:

As we head towards the winter months wild bird migrations will become more significant once again, with ongoing events across Europe and North America of concern in regard to implications to the UK.

On 3 November 2022, Dr Christine Middlemiss said:

We are seeing a growing number of bird flu cases on commercial farms and in backyard birds across the country driven by high levels of disease within wild birds. Unfortunately, we expect the number of cases to continue to rise over the coming months as migratory birds return to the UK, bringing with them further risk of disease that can spread into our kept flocks.

Figure 1, taken from the World Organization for Animal Health ‘World Animal Health Information System‘, shows the UK prevalence of high pathogenic bird flu between 2006 and 2022. In the graph, “deaths” refer to the number of birds that directly died from bird flu, “disposed of” refers to birds that have been culled/slaughtered for being infected or potentially infected.

Figure 1: Prevalence of high pathogenic bird flu in the UK, 2006–22

5. What is the UK government doing?

5.1 Regulations for domesticated birds

Animal health and welfare is largely a devolved issue. On 7 November 2022, DEFRA imposed mandatory housing for all poultry and domesticated birds in England. The measures built upon the existing Avian Influenza Prevention Zone that was declared across the UK on 17 October 2022. The Avian Influenza Prevention Zone mandates strict biosecurity regulations, including enhanced cleaning and disinfecting protocols, restricting personnel movement to essential purposes only, and ensuring measures are in place that deter wild birds from approaching bird enclosures.

Although mandatory housing is only compulsory in England, concerns have been raised about the growing number of bird flu cases in Northern Ireland, Scotland and Wales.

In October 2022, DEFRA announced a new package of measures to aid with the financial costs of the ongoing outbreak. Changes in the operation of the bird flu compensation scheme meant that affected farms can be compensated from the outset of planned culling rather than at the end. Relaxations on marketing regulations around defrosted poultry were also introduced. According to the new measures, farmers “have the option to slaughter their flocks early and to freeze these products, which can then be defrosted and sold to consumers between the period 28 November and 31 December 2022”.

5.2 Regulations for wild birds

In August 2022, DEFRA stated that evidence showed that “mitigation strategies are not very effective in reducing transmission within seabird colonies”. Therefore, DEFRA stated that its policy was to closely monitor the situation:

We recognise the significant threat posed by highly pathogenic avian influenza to the UK’s precious wild bird populations, but there are unfortunately limited effective actions that can be taken to protect them, as opposed to captive bird flocks. Our current policy is in line with international standards of best practice for disease control. The Animal and Plant Health Agency operates a robust, year-round programme of dead wild bird surveillance and clear public guidance has been issued not to handle their carcasses. Our new research consortium also funds research into how bird flu viruses are emerging in wild populations and helps us understand the risk posed to both domestic and wild birds.

However, Gwen Potter, the National Trust’s countryside manager for the Northumbria coast, said that although she welcomed the guidelines by DEFRA, they have come “far too late”.

5.3 Debates in the House of Lords and House of Commons

On 1 November 2022, Mark Spencer, the minister for food, made a statement in the House of Commons on the government’s response to bird flu. Mr Spencer said that outbreaks of bird flu in “kept and wild birds continue to occur on an unprecedented scale”. He said the government “recognises that the [food, farming and tourism] industries are under serious pressure”. However, he reiterated that the risk to public health “remains very low”. He confirmed that “mandatory housing measures for all poultry and captive birds are to be introduced to all areas of England from one minute past midnight on the morning of Monday 7 November”. The minister stated that any future decisions on “disease control measures, including the use of vaccination, will be based on the latest scientific, ornithological and veterinary advice”. He urged bird keepers to “adopt the best practice biosecurity advice measures required in the avian influenza prevention zone”.

MPs commented on the government’s statement and raised questions about the costs of the compensation scheme, the staffing of the Animal and Plant Health Agency, the development of specialised vaccines, and the regulations on the labelling of free-range products. The shadow minister for the environment, Daniel Zeichner, said the government statement “should have been made weeks ago, as the devastating impact on the wild bird population has been known for months and the impact on producers has been getting worse and worse week by week”. The Scottish National Party shadow spokesperson for the environment, Pete Wishart, welcomed the government’s announcement but clarified that Scotland was “not following the example of England on the mandatory housing of birds at this stage”.

The government’s statement was repeated in the House of Lords on 3 November 2022. In the subsequent debate, peers raised concerns about the practical challenges of the government’s compensation scheme, potential complications with the current freeze and thaw regulations, and the funding and focus on specialised vaccines.

On 16 November 2022, bird flu is the subject of an oral question in the House of Lords due to be asked by Lord Selkirk (Conservative).

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Cover image by Ciarán Ó Muirgheasa on Pixabay