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What is flu?

Please note the seasonal flu campaign for 2018/2019 ended on 30th April 2019. Next seasons flu campaign will launch in October 2019. 

Seasonal flu (also known as influenza) is a highly infectious illness caused by the flu virus.

The virus infects your lungs and upper airways, causing a sudden high temperature and general aches and pains.

You may also lose your appetite, feel nauseous and have a dry cough. You may need to stay in bed until your symptoms get better.

Symptoms can last for up to one week.

At risk groups

Flu affects people of all ages. Outbreaks of flu occur almost every year, usually in winter. This is why it is also known as seasonal flu.

Flu is more severe in people aged 65 years and over and anyone with a long-term medical condition. The HSE is urging people in at-risk groups to get the flu vaccine.

The difference between a cold and the flu

Flu symptoms come on suddenly with a fever, muscle aches, headache and fatigue. A cold usually starts gradually with a sore throat and a blocked or a runny nose. Symptoms of a cold are generally mild compared to flu.

Flu and cold symptoms


Seasonal flu



High fever lasts 3-4 days





General aches, pains

Usual; often severe


Fatigue, weakness

Can last up to 2-3 weeks

Quite mild

Extreme exhaustion

Early and prominent


Stuffy nose






Sore throat



Chest discomfort, cough

Common; can become severe

Mild to moderate; hacking cough

How serious is flu?

If you are healthy you will normally recover within 7 days, but you can recover more quickly. Flu can be severe and can cause serious illness and death, especially in the very young and elderly.

Complications of flu include bronchitis, pneumonia, ear infections and rarely acute encephalopathy (swelling of the brain). Severe disease and death are more likely if you have a chronic medical condition or you are older. Pregnant women are also at increased risk of flu complications.

Worldwide, flu causes between 3 and 5 million cases of severe disease each year and 250,000 to 500,000 deaths. Between 200 and 500 people, mainly older people, die from flu each winter.

How flu is spread

If you are carrying the virus, you can spread it by coughing or sneezing. This can happen from 1-2 days before symptoms develop and up to 5 days after symptoms develop.

Flu can survive on worktops and objects, especially in low temperatures and low humidity. You can get flu by touching a surface with the virus on it and then touching your mouth, eyes or nose. The virus can live on a hard surface for up to 24 hours and a soft surface for around 20 minutes.

More information


Getting the flu vaccine is a safe and effective way to help prevent flu, avoid hospitalisation and reduce flu-related illness and death.

You should recover at home within a week, without needing medical care. Contact your GP if you have severe symptoms or if you are in one of the high-risk groups.

If you are at home with flu or taking care of someone at home, follow these tips to help stop the flu spreading:

  • If you have the flu stay in one room with the door closed and, if possible, a window open
  • Family members should limit time spent with someone with flu and avoid sharing dishes, books, toys, etc
  • Avoid face-to-face contact with someone who has the flu
  • Discourage visits from people not living in the house
  • If you have flu, cover your nose and mouth with disposable tissues when sneezing or coughing. If tissues are not available, coughing or sneezing into your arm or sleeve (not hand) is recommended
  • Used tissues should be put into a bin and the bin sealed in the room and immediately taken outside for collection
  • Wash hands often with soap and water or alcohol-based hand rub, especially after coughing and sneezing
  • Everyone in the house should frequently clean their hands with soap and water or an alcohol-based hand rub, especially after every contact with someone with flu or their room or bathroom
  • Avoid touching the eyes, nose and mouth with your hands as this helps spreads the flu virus
  • Surfaces and items inside the house should be cleaned regularly with bleach-based household cleaners

The flu is responsible for 200-500 deaths each year in Ireland. In a severe season it can cause up to 1,000 deaths.

  • Flu can cause serious complications such as pneumonia, especially in those aged 65 and older, children under 4 years of age, those with long-term medical conditions and pregnant women
  • An increase in flu cases leads to an increase in heart attacks and strokes
  • Flu can cause serious disease in previously healthy people
  • The number of hospital cases last season was 2,218. 85 cases were admitted to critical care units
  • It is easy to pass on the flu and anyone infected can spread the disease from 1 day before symptoms begin (asymptomatic) and for 3 to 5 days after developing symptoms
  • Flu occurs every winter but it is not possible to know whether there will be a mild or a severe season in each year

Antiviral medicines like Tamiflu and Relenza are used to treat the symptoms of flu and to try to reduce the severity. They are only required for people whose symptoms are severe, or for people in the risk groups who develop the flu. The GP will decide on whether a person needs antiviral medicine or not.

Facts about flu