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What is flu?

The seasonal flu vaccine is available from October 2019 until the end of April 2020. 

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, headache, weakness and exhaustion. Symptoms can last for up to one week. You may need to stay in bed until your symptoms get better. Flu affects people of all ages. In some people flu can cause serious complications such as pneumonia.

How serious is flu?

The Flu virus is an unpredictable virus.

If you are healthy you will usually recover in 7 days. But Flu can be severe and can cause serious illness and death.

Complications of flu include bronchitis, pneumonia, ear infections and rarely acute encephalopathy (swelling of the brain).

Serious complications of flu are more likely if you have a chronic medical condition or if you are aged 65 years or older. Pregnant women are also at increased risk of flu complications.

In Ireland, between 200 and 500 people, mainly older people, die from flu each winter.

Every year, around the world, flu causes between 3 and 5 million cases of severe disease and up to 646, 000 deaths.

At risk groups

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

  • People aged 65 years and over
  • Pregnant women
  • People (adults and children) with long-term medical conditions such as diabetes, heart disease, liver, kidney disease, cancer, chronic lung disease including COPD, or neurological diseases
  • People whose immune system is impaired due to disease or treatment including cancer patients
  • Persons who are obese who have a body mass index (BMI) of over 40
  • People with Down syndrome
  • Residents of nursing homes and other long-stay institutions
  • Healthcare workers
  • Carers and household contacts of people at medical risk of the complications of flu
  • People with regular close contact with poultry, water fowl or pigs

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 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 aged 65 years and older, are pregnant, or if you have a long-term health condition that puts you at risk of complications of flu.

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 maycause up to 1,000 deaths.

  • Flu can cause serious complications such as pneumonia, especially in those aged 65 and older, pregnant women and children and adults with long-term medical conditions
  • An increase in flu cases leads to an increase in heart attacks and strokes
  • Flu can cause serious disease in previously healthy people
  • Every year, hundreds of people are hospitalised with flu. In 2017/2018, which was a severe flu season, more than 4000 people were hospitalised with flu and 191 people admitted to critical care (intensive 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.