Key messages

Prevention makes a difference

Flu transmits easily from person to person. It does this through the air or from contaminated hands or surfaces. The risk of getting or causing infection is easily reduced by taking some simple preventive steps. Immunisation in particular decreases the risk of a person being infected. Proper use of flu vaccines is the most effective form of protection.

All flu viruses spread easily from person to person through droplets from the coughs and sneezes of infected people. The virus is able to temporarily survive outside the body, so transmission can also occur from freshly contaminated hands, objects and surfaces such as handkerchiefs, doorknobs and taps.

Although it is thought that infected people may be able to spread influenza just before they start feeling sick, it is when a person has symptoms that they are most infectious. Young children, severely ill people, and those who have weakened immune systems may infect others for longer periods. Individuals who become infected but never develop recognisable symptoms can also transmit infections.

Daily preventive habits are one of the most important actions for stopping the spread of the flu. The three simple rules of prevention are:

  • Stay home if you are sick with what may be flu.
  • Wash hands frequently and properly.
  • Cover your mouth when coughing and sneezing. Use a tissue, and dispose of it properly. If no tissue is available, cough or sneeze into your elbow rather than your hand.


Flu vaccination is the most effective way of protecting yourself. Based on the viruses seen in the previous season, the vaccine is made available in advance of the flu season, containing three components (trivalent vaccine) selected to protect against the main groups of influenza viruses. The recommended composition of viruses in the flu vaccine is defined annually by the World Health Organization (WHO).

Influenza remains a threat

Annual influenza epidemics are associated with high morbidity and mortality. ECDC estimates that up to 40,000 people in the EU/EEA die prematurely each year due to causes associated with influenza. This figure is in line with estimates from a number of EU countries and the average number of annual influenza deaths estimated in the United States.

The severity and pattern of influenza infection and disease varies from year to year depending on the characteristics of the virus. A large proportion of influenza-related deaths occur in individuals older than 65 years. However, the disease can have a severe clinical course in individuals of any age with chronic underlying conditions. Influenza can cause exacerbations of pulmonary and cardiovascular disease in individuals that suffer from such conditions and can cause death due to heart attacks or strokes in older people.

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Influenza affects many people every winter

Influenza is a contagious disease which can have serious outcomes. However, it is often preventable. Understanding how the disease infects and how one can prevent infection is key to reducing the number of illnesses, hospitalisations and premature deaths.

Influenza is a contagious respiratory illness caused by infection with an influenza virus. In Europe, influenza occurs in regular annual epidemics in the winter season. Usually, winter epidemics affect each European country for one to two months and, across Europe as a whole, last for about 4 months. Sporadic infections also occur outside of the influenza season, though the incidence is very low in the summer months.

Not everyone who becomes infected gets sick, but for those that do, common symptoms can include fever, cough, sore throat, aching muscles and joints, headache and general malaise. Symptoms are similar to those of many other respiratory infections; however, influenza is often more severe than a simple cold.
In uncomplicated cases, symptoms resolve spontaneously within one week from onset. There is a wide range of severity of infection and illness, from no symptoms at all, through to severe illness including pneumonia and encephalitis. Severe illness may be caused directly by the influenza virus or result from other bacterial or viral infections that occur after flu has lowered the body’s defences. Pre-existing respiratory and cardiovascular diseases may be made worse: these can be life-threatening.

Severe illness and complications are more common in certain risk groups; these include those with other chronic medical conditions like diabetes, immunosuppression or cardiovascular and respiratory diseases, older individuals (often classified as 65 years and older). Some studies have pointed to an increased risk of severe disease in very young children and pregnant women. Severe illness due to influenza can occasionally occur in healthy people outside any of these groups, though this is rare.

The epidemiology and clinical features of influenza can be different during pandemics, depending on the characteristics of the virus and on the level of immunity in the population to a virus that is different to those that have circulated in previous influenza seasons. This was the case during the 2009 influenza A(H1N1) pandemic, where the highest incidence of infection and disease was in younger individuals (under age 65 years).