What is bird flu and why is it back in the news?

What is avian flu?

Avian influenza, also known as bird flu, is a contagious viral disease in animals, caused by a virus loosely related to human influenza. Some strains of the disease have been passed to humans but this is very rare, and usually occurs only after very close contact with infected birds or animals. While all bird species and, less commonly, pigs are thought to be susceptible, domestic poultry flocks are especially vulnerable to infection. Outbreaks can rapidly result in epidemics among bird populations. Public health authorities are concerned about the potential of the virus to mutate into subtypes capable of causing human disease. As a result they warn there is always a threat of a new influenza pandemic emerging.

Why is it in the news again?

The UK has been hit by a record outbreak that has resulted in 500,000 captive birds being culled this autumn. An avian influenza prevention zone was declared across the UK at the start of November, requiring strict biosecurity measures and all birds to be kept indoors.

What are the most dangerous strains?

The NHS says there are four strains that have caused particular concern in recent years. The first, identified in 1997, was H5N1, followed by H7N9 in 2013, H5N6 the following year and H5N8 in 2016. The H5N1 form has been the cause of most concern in recent years and the UK government has said particular safety measures were put in place in parts of North Yorkshire on 21 November after confirmed and suspected cases of that strain in poultry in the area.

Where has it appeared?

The chief veterinary officer, Christine Middlemiss, has said there are 40 infected premises in the UK. They include 38 in Great Britain – of which 33 are in England – and two in Northern Ireland. By comparison, there were 26 outbreaks last winter.

A rare white-tailed eagle found dead on Skye is among the wild birds to have tested positive, after a postmortem by the pathology unit at Scotland’s Rural College. It is thought to be the first detected case involving an eagle in Scotland. The adult eagle, from a well-established territory on the Trotternish peninsula, was found dead on 14 November. Ornithologists believe it may have fed on infected greylag geese.

Some 22,100 ducks were culled at a commercial premises in Aughnacloy, Co Tyrone, while culling and an exclusion zone was also being applied to a second site in Broughshane, Co Antrim, described as a “small backyard flock”.

If it just affects birds, why the panic?

It doesn’t. World Health Organization (WHO) figures show that from 2003 to 2021 there were 863 confirmed cases of the H5N1 virus in humans. Of these cases, 456 people died. While transmission is rare, it has happened.

So far, most of the human deaths have been in countries in Asia, in communities in which people live in close proximity to poultry. Although it does not easily infect humans, every time it does it increases the chance that the virus could mutate into a form that could be passed from one infected human to another. The WHO fears this could lead to a flu pandemic.

How do you catch bird flu?

It is very unlikely you will catch the virus unless you have been in close contact with infected birds or someone with confirmed or suspected bird flu. The virus is found in secretions from the eyes and respiratory tract, and droppings of infected birds. Humans can catch the virus by inhaling droplets sneezed by infected birds or the dust from their bedding or droppings.

What are the symptoms in humans?

They vary depending on the strain. Most infections have flu-like symptoms including fever, coughing, sore throat, runny nose, and aches and pains. Symptoms of the H5N1 subtype are more severe and frequently result in death. Other symptoms can include conjunctivitis – red, sore and discharging eyes.

How does it spread?

WHO scientists have said they believe it is likely the virus is carried by migrating birds. More recently the UK government has said it “spreads from bird to bird by direct contact or through contaminated body fluids and faeces”. Officials added: “It can also be spread by contaminated feed and water or by dirty vehicles, clothing and footwear … Avian influenza isn’t an airborne virus.”

It can spread to humans who touch infected birds, droppings or bedding or who kill or prepare infected poultry for cooking, the NHS has said. People cannot catch bird flu by eating fully cooked poultry or eggs, even in areas affected by an outbreak, health officials have said.

What measures is the UK taking?

The government has said the chief veterinary officers for each of the UK’s constituent nations have “agreed to bring in new housing measures to protect poultry and captive birds from avian influenza following a number of confirmed cases across Great Britain in recent weeks”. It added: “The new housing measures, which will come into force on Monday 29 November, mean that it will be a legal requirement for all bird keepers across the UK to keep their birds indoors and to follow strict biosecurity measures in order to limit the spread of and eradicate the disease.”

How do you spot the virus in birds?

Symptoms in infected birds include a swollen head and blue discoloration around the neck and throat. They will also show signs of breathing problems including gaping beaks, coughing, sneezing and rattling wheezing. Poultry farmers will also notice a loss of appetite in the infected birds and a decrease in egg laying.

People are advised not touch or pick up any dead or visibly sick birds they find. In Great Britain, dead wild waterfowl or other wild birds should be reported to Defra. Some will then be collected and tested to help scientists understand how the disease is distributed geographically and in different types of bird.

What drug treatments are available to humans?

There is no vaccine for avian flu. If a person were infected, the NHS has said they would be either told to stay at home or put into isolation in hospital. They would then be treated with an antiviral medicine such as oseltamivir (known as Tamiflu) or zanamivir (known as Relenza).

Scientists have found that such treatments “help reduce the severity of the condition, prevent complications and improve the chances of survival. They are also sometimes given to people who have been in close contact with infected birds, or those who have had contact with infected people, for example family or healthcare staff,” the NHS said.