Seasonal influenza (flu)
What is influenza (Flu)?
Seasonal influenza, commonly known as the flu, is a contagious viral infection that re-emerges each year during the colder months. Caused by influenza viruses, the flu spreads through respiratory droplets when infected individuals cough, sneeze, or talk.
Symptoms may include fever, cough, sore throat, body aches, and fatigue.
Vaccination remains the most effective method to prevent the flu and its potentially severe consequences. The Public Health Agency recommend annual flu vaccination, which helps protect individuals and contributes to community immunity, reducing the overall burden of the disease.
Apart from vaccination, practicing good hygiene, such as handwashing and avoiding close contact with sick individuals, can help reduce the risk of contracting and spreading the flu. As the flu virus can change from year to year, ongoing surveillance plays a vital role in updating vaccines and informing public health strategies.
Flu is most common during the winter months and usually peaks between December and March in the Northern Hemisphere.
Types of influenza:
There are two main types of influenza that cause illness:
- Influenza A - usually causes more severe illness
- Influenza B - can also cause infection, but is generally milder
The influenza virus changes constantly, with new strains and variants emerging every year. Because of this, annual vaccination is recommended to provide best protection.
Who is at higher risk from Flu?
For most people, flu is unpleasant, but not serious. However, some people are more at risk of sever illness and complications. You are considered 'at risk’ if you are:
- pregnant (at any stage of pregnancy)
- aged 50 or over on 31 March 2024 (even if you feel fit and healthy)
- a child or adult with certain medical conditions, including (chronic chest condition (such as asthma), chronic heart condition, chronic liver disease, chronic kidney disease, diabetes, lowered immunity due to disease or treatment such as steroids or cancer therapy (people living in the same house as someone with lowered immunity may also need to be vaccinated), a chronic neurological condition (such as stroke, multiple sclerosis, cerebral palsy, or hereditary and degenerative diseases of the central nervous system or muscles), serious medical condition (check with your doctor if you are unsure)
- a child who has previously been admitted to hospital with a chest infection
- a child attending schools for children with severe learning difficulties
- living in a residential or nursing home
- a main carer for an older or disabled people
How to get a free flu vaccine
If you are in a an 'at risk' group, you are eligible for a free flu vaccine on the HSC through your local GP practice.
Where to get vaccinated
- Adults and eligible children - Contact your GP practice to book your flu vaccination
- Primary school children and Year 8 pupils - Will be offered the flu vaccine at school
- Children aged 2-4 years - Eligible for a free flu vaccine through their GP practice
Children are also vaccinated to help prevent the spread of flu to vulnerable people.
Flu complications
Flu can lead to serious complications, including bronchitis, secondary bacterial pneumonia. These complications may require hospital treatment and can be life threatening - especially for the elderly, those with asthma, and individuals in poor health.
Seasonal flu surveillance information
PHA has integrated influenza, respiratory syncytial virus (RSV) and COVID-19 reporting into a new report to provide a single overview of the epidemiology of these infections.
- Weekly - Respiratory surveillance report
- Seasonal weekly - COVID-19 Spring 2025 vaccination weekly report
- Annual - Seasonal influenza - annual surveillance reports
Flu related resources
- Flu | nidirect
- Flu | NHS (external link opens in a new window / tab)
- Seasonal influenza: guidance, data and analysis | Public Health England
- Reducing the spread of Coronavirus (COVID-19) and other respiratory infections
- How to use your health services
- Flu is more serious than you think (leaflet and translations)(external link opens in a new window / tab)
- Flu is more serious than you think: pregnant women (leaflet and translations)(external link opens in a new window / tab)
- Hand hygiene