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Avian influenza: All you need to know about the bird flu outbreak

Published: 25th January, 2022 at 18:00
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It’s the worst-ever outbreak of avian influenza (bird flu) on record. Here’s what we know so far.

The UK is currently experiencing its worst-ever outbreak of avian influenza, and more cases of the highly pathogenic H5N1 strain have been recorded in recent days. Outbreaks of avian flu can have devastating implications for farmers and poultry owners (including those with backyard chickens) as well as the surrounding areas.

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Restrictions are in place across England, Scotland and Wales to mitigate the spread of the virus among kept birds. It is currently a legal requirement that all commercial flocks, pet birds and backyard flocks must be kept indoors, and biosecurity measures are followed.

Wild birds are also severely affected by the avian influenza outbreak, with charities such as the RSPB calling for urgent action to reduce the impacts. The Svalbard barnacle goose, a migratory goose that spends winter in the UK, recorded a drop in numbers from 43,703 last year to 27,133 this year – a 38 per cent decline.

What is bird flu?

Avian influenza, or bird flu, is a highly infectious type of influenza that mainly affects birds, although in rare instances it can also affect humans and other mammals.

Some bird species, such as wild ducks and geese, can be infected with bird flu viruses, but often don’t become ill from it. Birds that are infected will have the virus in their saliva, mucous and faeces. If the virus spreads to domestic poultry, it can cause serious illness and death.

There are two types of avian influenza, Low Pathogenicity (LPAI) and High Pathogenicity (HPAI). LPAI is mostly harmless and will typically cause little or no clinical signs in infected birds.

HPAI, on the other hand, is highly contagious and kills almost all infected poultry.

Avian flu will spread from flock to flock, as infected birds are moved to a new location where they are mixed with healthy birds. It can also spread among kept birds through deposits on clothing and shoes, and a study published in the Indian Journal of Virology found that the H5N1 strain can live in wet or dry manure for up to eight weeks. So, a virus on mucky wellies can be spread to a healthy flock, weeks, or even months, later.

The virus can also spread through migrating waterfowl droppings, so it’s important to limit contact with wild birds where possible.

Read more about flu:

Where has bird flu been detected?

The government has confirmed 71 cases of avian influenza H5N1 at multiple locations across England, one case in Wales and two cases in Scotland.

On 25 January, the highly pathogenic avian influenza (HPAI) H5N1 was also confirmed in poultry near Byker, and as with previous occurrences in the UK, a 3km (1.9 miles) Protection Zone and a 10km (6 miles) Surveillance Zone has been put in place, however, these zones do not restrict the movement of people.

Avian influenza outbreak, 25 Jan 2022, © arcGIS
Locations of avian influenza in the UK, as of 25 January 2022. © arcGIS

At present, an Avian Influenza Prevention Zone is active across the whole of the UK to limit the risk of the disease spreading.

In the US, a lab analysis from the US Department of Agriculture has recently discovered the highly pathogenic Eurasian H5 avian influenza (HPAI) in a wild American wigeon (a type of duck) in South Carolina, which is the first time it’s been detected in the country since 2016.

Has bird flu been detected in humans?

At the start of this year, the UK Health Security Agency (UKHSA) confirmed a case of avian influenza in a human living in the Southwest of England. Swabs were taken and laboratory analysis confirmed that it was the H5 type as found in birds. The case was found to have been contracted through very close, regular contact with a large number of infected birds.

“Currently there is no evidence that this strain detected in the UK can spread from person to person, but we know that viruses evolve all the time, and we continue to monitor the situation closely”, Chief Scientific Officer at UKHSA, Professor Isabel Oliver said. “It remains critical that people do not touch sick or dead birds, and that they follow the DEFRA advice about reporting.”

In a report published on 25 January, the Centre for Health Protection in Hong Kong confirmed that a 5-year-old boy has died from the H9N2 strain of the avian influenza virus, in addition to 10 deaths previously reported in late 2021.

A report from the World Health Organisation (WHO) said that 863 cases of human infection with avian influenza (H5N1) virus had been reported globally from 18 countries between January 2003 and 13 January 2022. Of these cases, 456 were fatal, giving a Case Fatality Rate (CFR) of 53 per cent.

Avian influenza
Migratory waterfowl including ducks, geese, swans, and gulls, pose a threat as they can introduce avian flu to an area where poultry, game birds, pets, and other captive birds are kept. © Getty Images

How does bird flu spread to humans?

Risk to the general public is considered low, and most cases of reported avian flu occur after direct (unprotected) contact with infected birds or contaminated surfaces. Direct contact can include touching infected birds, droppings or the birds' bedding, killing infected birds or preparing them for cooking, and subsequently touching the eyes, nose or mouth.

Avian flu is not an airborne virus, although it can survive in the air for a limited time. As birds flap their wings, scratch, or shake their heads, they can send particles up into the air, where the virus can survive in droplets or dust. From here, the virus can enter through the eyes, nose or mouth.

What are the symptoms of avian flu in humans?

The symptoms of bird flu in humans can range in severity and resemble conventional influenza, including:

  • A very high temperature, feeling hot or shivery
  • Muscle ache
  • Headache
  • Cough
  • Shortness of breath
  • Sore throat

Other symptoms may also include diarrhoea, stomach pain, sickness, chest pain, bleeding from the nose and/or gums, and conjunctivitis (eye infection).

Symptoms of bird flu in chickens

One of the problems in detecting avian flu is that birds infected with the virus can show no initial symptoms. This means that it spreads easily, especially in the early days of infection. Symptoms of bird flu in poultry and captive birds include:

  • Appetite loss
  • Wet eyes
  • Decreased egg production
  • Decreased roaming
  • Excessive huddling among the flock
  • Ruffled feathers
  • Fluid in the comb and wattles
  • Coughing
  • Blueness in head area or swollen head
  • Legs bleeding under the skin
  • Increased mortality (sudden death)
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What do I do if I think my chickens have bird flu?

If you suspect any type of avian influenza in poultry or other captive birds, you must quarantine the bird (s) and report it immediately by calling the Defra Rural Services Helpline on 03000 200 301 in the UK and by contacting the United States Department of Agriculture in the US.

Authors

Holly SpannerStaff Writer, BBC Science Focus

Holly is the staff writer at BBC Science Focus. Before joining the team she was a geoenvironmental consultant and holds an MSc in Geoscience from UCL.

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