Influenza in animals

What is influenza?

Influenza (flu) is an easily spread respiratory infection caused by the influenza virus. There are three types of influenza virus, A, B and C and types A and B cause human infection. When a person catches flu, they develop antibodies (immunity) to the strain of influenza virus which infected them. These antibodies protect them against that strain and may provide some protection against other similar influenza virus strains. Influenza viruses infect people every year - generally in winter (this is known as seasonal influenza). 

Influenza viruses constantly mutate (change), and each time they do, fewer people will be immune to that new strain. When a significant change occurs to the influenza virus, a new strain of flu appears, against which many people will not have immunity.  That strain of influenza virus may spread around the world causing a flu pandemic – the last flu pandemic was in 2009. See here for Frequently Asked Questions on flu.

What is swine influenza (swine flu)?

As well as people, birds (which are made ill by avian influenza) and animals, such as pigs, can be infected by influenza viruses. These bird and animal influenza viruses can go on to infect people.   

Swine influenza is a respiratory disease of pigs caused by certain types of influenza viruses known as swine influenza (flu) viruses that regularly cause outbreaks of influenza in pigs.  When pigs develop influenza, they may have no symptoms, or they may develop symptoms similar to flu symptoms in humans. Swine flu viruses are generally different from those that affect humans and birds. Pigs can be infected by different types of influenza viruses - the main types of swine flu viruses are influenza  A(H1N1), A( H1N2), and A (H3N2). It is uncommon for swine influenza viruses to infect humans.

What is the current threat to Ireland of swine flu?

Overall, the threat to Ireland from swine flu is currently very low. Swine influenza is present in pigs in many countries around the world, and has caused swine influenza outbreaks among pigs, including in Ireland.

In the UK recently (November 2023), a case of swine flu caused by variant influenza A (H1N2)v was identified in a person for the first time in the UK. This person has recovered fully from their illness. Because this was an unusual event, the UK is investigating this person, as they do not appear to have had any direct contact with pigs. Although swine flu A(H1N2) does not spread easily from pigs to people, the UK will be keen to ensure that there is as little spread of this virus as possible, and that as few people as possible catch this virus strain. HPSC is closely monitoring the situation in the UK.

Why is it so important to prevent swine flu infections in people?

Swine flu viruses do not usually infect humans, but occasionally people have become infected. When a flu virus that normally spreads in pigs - but not people - is found in a person, it is called a variant flu virus. The name of the variant flu virus being investigated in the UK at the moment is variant influenza A(H1N2)v.

The great majority of human infections with variant flu viruses do not lead to person-to-person spread. However, each person infected with a swine flu virus must be fully investigated to make sure that such viruses are not spreading easily between people. 

Flu viruses are always mutating. At present, swine flu viruses do not spread easily between people. However, if a person catches swine flu when they are already sick with seasonal human flu, the virus could become better at spreading between people. When both viruses are present in the same person, this could allow the two viruses to mix and change to a type that spreads more easily between people, increasing the risk of a flu virus developing that could lead to a pandemic, as happened last in 2009.

Who is most likely to be infected with swine flu?

While it is uncommon to catch swine flu from pigs, people who are in close contact with infected pigs or contaminated environments have an increased risk of catching swine flu, including people who raise or work with pigs and workers in the pig industry, and their families. This is thought to happen when an infected pig coughs or sneezes and droplets with flu virus in them spread through the air. If these droplets land in a person’s nose or mouth, or are inhaled, the person can be infected.

What are the symptoms of swine flu in people?

These are similar to ordinary seasonal influenza, including shivering, fever, sore throat, muscle pains, headache, coughing and weakness. Symptoms may be very mild. Symptoms tend to last about a week or so. 

Are there any tests for swine flu?

Yes, the usual tests for seasonal flu will tell your doctor if you have flu. Further advanced tests can be done to identify if the strain of flu is swine flu.

Is there any treatment for swine flu?

Swine flu is treated in the same way as seasonal flu. Most people who develop swine flu or seasonal flu and who are otherwise healthy don’t need special drugs or treatment. If a person has been diagnosed with flu, simple medication such as paracetamol or ibuprofen for fever, headache and muscle aches is all that is needed. The person should drink plenty of fluids and get plenty of rest. They should stay at home until they have had no symptoms for 48 hours.  If the person is in a risk group for influenza or have  worsening symptoms, they should contact their GP who may decide to prescribe antiviral medications for the treatment of influenza. You can find more information here.  

Can I catch swine flu from eating pork or bacon?

There is no evidence that properly cooked pork or bacon can infect people with swine flu. At present, there are no known swine flu infected pigs in Ireland. Even if swine flu is detected in pigs in Ireland, there is no evidence that properly cooked pork or bacon can infect people with swine flu. Irish pork and bacon, when properly cooked, are perfectly safe to eat.

How can I avoid getting swine flu?

The best way to protect your health is to make sure that you are vaccinated against seasonal influenza. This vaccine will not protect you against swine flu, but it will protect you against seasonal influenza. People having contact with pigs should wear appropriate out-wear and footwear and ensure any items that come in contact with pigs are sanitised after contact. People should avoid eating, smoking or vaping around animals. Hands should always be properly washed after any contact with animals.

Published: 8 December 2023