Introduction

As of October 2024, 20 human cases of avian influenza (bird flu) have been reported in the United States. All cases, except one, have been linked to exposure to poultry or cows infected with the H5N1 virus, which is one viral strain responsible for causing bird flu.¹ 

In the UK, the last outbreak of avian influenza ended in March 2024. However, bird flu was detected in populations of wild birds in October 2024.²

The risk of bird flu infection to the general public is low and it should be noted that, overall, the transmission of bird flu to humans is rare. Those who work with poultry, however, are at an increased risk of catching this virus. There are certain precautions that farmers and poultry workers can take to minimise this risk, which will be addressed in this article.

What is avian influenza?

Avian influenza, commonly referred to as bird flu, is a zoonotic virus (one that can spread from animals to humans). Currently, there are four viral strains of significance: H5N1, H7N9, H5N6, and H5N8. Although a rare occurrence, all four strains have been associated with human cases of bird flu.³ The strain H5N5 was detected in wild birds in the UK in October 2024.

Avian influenza is a virus that primarily infects birds, including both domestic and wild bird species. Waterfowl (e.g., ducks and geese) and gulls are particularly susceptible.

There are two types of bird flu: low-pathogenicity avian influenza (LPAI) and high-pathogenicity avian influenza (HPAI). The former causes mild to no symptoms and can prevent hens from laying eggs. The latter causes more severe symptoms and can be fatal in birds.⁴

The virus is shed in the faeces, mucus, and saliva. Bird flu can then be transmitted through direct contact with these bodily fluids or contaminated food or water. The virus is hardy and can survive at low temperatures for a long period of time; it can therefore persist and be spread via farm equipment. The virus can be caught from infected animals, both dead and alive.³

The following are sometimes seen in birds infected with avian influenza:⁴

• Reduced eating and drinking
• Lethargy, for example, lying down for extended periods
• Breathing difficulties
• Swollen head and neck
• Sudden death, which can occur without prior symptoms

In humans, symptoms of bird flu include those typical of flu: cough, muscle aches, headache, and a high fever. Conjunctivitis and bleeding nose and gums can also be seen. Importantly, the infection can lead to more severe complications, such as pneumonia.³

What strategies can farmers and poultry workers take to reduce their risk?

People who work with birds and come into close contact with them should follow biosecurity measures. These are precautions that are taken to prevent the spread of harmful viruses.⁵

• Birds should be kept in their own building. This will prevent them from encountering other birds, such as wild ducks and geese, which may carry LPAI and not show symptoms of the virus. Food and water for birds must be kept inside too, and the building needs to be adequately maintained. Any holes, leaks, or blocked drains must be repaired to prevent infected birds or contaminated water from entering the building
• Deterrents should be set up to scare off wild birds. For example, scarecrows and reflective items can be used to ward off birds that might be carrying the virus
• Surfaces need to be cleaned with disinfectant approved by the Department for Environment, Food & Rural Affairs (Defra). This includes walkways, wheelbarrows, containers, plastic egg trays, and vehicles. The disinfectant must be used according to the manufacturer's instructions to be effective
• Only clean clothing and footwear should be worn when amongst poultry. This will prevent any virus present on clothing from entering birdhouses. Clothing or overalls should be worn in each birdhouse if there are multiple buildings housing birds. Contaminated water can easily be picked up from the ground by footwear. Shoes should therefore be cleaned with a disinfectant foot dip before entering the birdhouse
• Records should be kept of all visitors to birdhouses. This is so the individual can be contacted if avian influenza is confirmed on the premises
• New birds must have their health checked before they are brought onto the premises. They should be kept separate from the rest of the birds. Any movement on and off the premises, food and water consumption, and the number of eggs produced should be recorded. Regular checks for symptoms in birds should be carried out in order to spot any behavioural changes which might indicate avian flu. For example, reduced eating and drinking or producing fewer eggs can be symptoms of the virus. If you suspect a case of avian influenza, it is imperative that this is reported to the appropriate authorities (Animal and Plant Health Agency, in the UK) as soon as possible. Dead birds previously infected with the virus must be disposed of in the correct way as soon as possible

To avoid catching bird flu, personal protective equipment (PPE) is essential. Coveralls and gloves should be worn, ideally disposable, or reusable PPE that can be washed and disinfected. Rubber or polyurethane boots that can be cleaned are recommended. A suitable grade of mask (and goggles), for example, an FFP3 respirator with an exhalation valve, is advised.⁶

Staff working with poultry need to be trained on how to properly don and doff PPE (putting on and taking off equipment).⁷ After removing PPE, you should always wash your hands thoroughly.⁸

Is there a vaccine for avian influenza?

In the UK, it is not permitted to vaccinate birds against avian influenza. This is because it is still possible for vaccinated birds to get infected but not show any symptoms. If asymptomatic birds are allowed to be traded, this would make it almost impossible to track the virus once it has started to circulate. There are also concerns that vaccination can give a false sense of security to poultry workers and farmers, and this might mean they are not as vigilant when upholding biosecurity measures.⁹

There is no human vaccine specifically for avian flu. However, poultry workers are offered the seasonal flu vaccine. It is important to note that the seasonal flu vaccine does not protect against avian influenza. The seasonal flu vaccine is offered to poultry workers because this reduces the chance of them catching both seasonal flu and avian flu at the same time. This would be risky because it could lead to the creation of a new virus through a phenomenon known as genetic reassortment. This new virus could cause a dangerous disease similar in severity to bird flu but which spreads as easily as seasonal flu.

What happens if you catch avian influenza?

If someone is suspected of having bird flu, they will be told to stay at home and isolate as much as possible. They may alternatively be treated in hospital, albeit away from other patients. Antiviral medicines, like Tamiflu and Relenza, might be given to fight the infection.³

In the UK, if avian influenza is thought to be present, the Animal and Plant Health Agency should be contacted. The agency will ensure that farm staff are protected from being exposed to the virus and are monitored and treated, if needed. In cases where avian influenza is confirmed, all poultry must be culled in the most humane way possible.¹⁰ This highlights why taking adequate precautions is so important: the consequences of avian influenza can cause the large-scale loss of animal life and a huge economic cost to farmers.

Summary

• Avian influenza (also known as bird flu) is a highly contagious zoonotic virus that poses a low risk to humans, although cases in humans have been reported
• The virus is spread via contact with the faeces and respiratory secretions of infected animals (either dead or alive)
• There are various biosecurity measures that farmers and poultry workers can take to reduce the risk of avian influenza. These include keeping birds away from wild birds, regularly cleaning equipment using Defra-approved disinfectants, and wearing PPE
• Since farmers and poultry workers are in close contact with birds, they are offered the flu vaccine to reduce the risk of catching seasonal and avian influenza simultaneously