Influenza, or flu for short, is caused by the flu virus (influenza virus). It is an infectious respiratory disease. People often refer to all types of illnesses with symptoms like a cold, cough and fever as ‘flu’, but these symptoms can also occur with other viruses, such as the coronavirus. The information on this page only concerns actual flu, caused by the influenza virus.
What is flu?
Influenza, or flu for short, is caused by the flu virus (influenza virus). It is an infectious respiratory disease. You can infect others by coughing and sneezing. The illness is brought on by inflammation of the airways. You suddenly get a high fever, headache, muscle aches and cold shivers. Flu occurs every year in the Netherlands, usually in the winter months. We call this seasonal flu. Because there are various types of flu viruses and they are constantly changing, people can get flu more than once.
What are the symptoms of flu?
Flu is a disease in which the mucous membranes of the airways become inflamed. It often begins suddenly with:
- cold shivers
- a runny nose
- a headache
- severe muscle aches and fatigue
- a sore throat and dry cough
- a (high) fever
The fever can rise to 39 °C or higher within 12 hours and typically lasts three to five days. Full recovery takes one to three weeks. Flu is usually harmless and most people recover without medication. Some people are at a higher risk of becoming seriously ill from the flu virus. They can become extremely short of breath or develop pneumonia. This is especially true for the elderly and people with a chronic illness. For people who already have heart and lung problems, flu can make their symptoms worse.
How do you get flu?
The flu viruses are found in droplets of snot, mucus and saliva. The viruses are spread through talking, coughing and sneezing.
Monitoring the flu virus
RIVM monitors the development of the flu virus in various ways. We call this ‘surveillance’. As part of these efforts, we work closely with Nivel, Erasmus University Medical Center (Erasmus MC) and laboratories in the Netherlands. We track how many people there are in the Netherlands with flu-like symptoms and look at which type of flu virus is most prevalent. The current status of the spread of flu in the Netherlands can be found on the Facts and figures page.
How common is flu in the Netherlands?
The prevalence of flu is different every year. In the 2021–2022 flu season, the flu epidemic began later than in previous seasons and lasted 13 weeks. Approximately 127,378 people visited their GP with flu-like symptoms. This was less than normal: many people with these symptoms went to get tested for the coronavirus at their Municipal Public Health Service or took a self-test and did not go to their GP. It is estimated that around 795,000 people had flu between October 2021 and May 2022. People mainly became ill from the type A(H3N2) flu virus. The current status of the spread of flu in the Netherlands can be found on the Facts and figures page.
Flu and COVID-19
Flu and COVID-19 are both respiratory infections, but they are caused by different viruses. Both viruses are spread through droplets that are released when someone coughs or sneezes. Both viruses also cause fever, cold-like symptoms and a cough, and sometimes pneumonia. The basic recommendations to prevent the spread of the coronavirus also work to prevent the spread of the flu virus. Washing your hands frequently, coughing and sneezing into the fold of your elbow and social distancing reduce the risk of passing the virus to others. Keep these recommendations in mind, especially when coming into contact with vulnerable groups of people. They can become seriously ill from the flu virus.
Flu and COVID-19
