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By Bjarne Lühr Hansen PhD, MD and Philipp Skafte-Holm MD, Mentor Institute

It varies a lot how ill people become from influenza. Especially older people and people with a weak heart or smoker’s lungs become very ill. It is recommended that persons with chronic diseases, elderly, obese and pregnant women are vaccinated in October or November every year. Influenza can lead to pneumonia.

Influenza is caused by virus. There are several different kinds of influenza virus called A, B and C, respectively. Influenza virus A and B causes you to become most ill, while type C only causes light nuisances. Influenza occurs from the middle of December to the middle of March. With 3 to 4 years interval, many people become ill with influenza – in that case it is an epidemic.

It varies a lot how ill people become. It ranges from barely noticing the illness to staying in bed for several days. Especially infants, older people and persons with heart or lung diseases become very ill.

Typically, the illness starts with chills, fast rise in temperature to 39-40ºC, strong headache, pains everywhere and pains when moving the eyes together with hoarseness and dry cough. After 2 to 3 days, the temperature drops and thereafter you recover fast. Some are, however, tired for 1 to 2 weeks after the temperature has dropped to normal.

Fever for more than 5 days can be a sign of a complication of a bacterial inflammation. Influenza is bad enough but it is the bacterial complications that cause the real problems. The most frequent complications are pneumonia and inflammation of the middle ear.

There are effective vaccinations for influenza. It is recommended that elderly people (over 65 years), obese (BMI over 40), people with chronic diseases and pregnant women (more thant 12 weeks pregnant) are vaccinated. You should be vaccinated in the period of October to November; however, if you are late it is still a good idea to speak to your general practitioner about the possibility of vaccination anyway. The vaccine protects after 1 to 2 weeks and the protection ends a few months after the vaccination. This is why it is necessary to have the vaccination every year.

Click to read about how to assess the sick.


Influenza is highly contagious. The infected area covers your entire home. The illness is transmitted from ill to healthy people through the air. The ill infect 24 hours before they fall ill and up to 2 days after they have recovered. Therefore, it is difficult to avoid contagion with influenza. It takes 1 to 3 days from you have been exposed to contagion till you fall ill.

When can I go to work?

When the fever has disappeared. There is no reason to drag yourself to work with a fever, you are just going to infect your colleagues.


There is no reason to take antibiotics – it has no effect on influenza. However, there is medication for influenza that shortens the period where you are ill with around 1 day. The medication should be taken as early as possible (within 48 hours after the influenza has started) – or else it has no effect. Your doctor can prescribe the medication.

It is a good idea to take antipyretics (aspirin or paracetamol) for example for the night, since they give you a calmer sleep. Ibuprofen can be good for the muscle pain you have in connection with influenza.

What can you do?

You should dress lightly and stay in a cool room to make the fever drop. You should drink plenty, since you lose fluid.

Contact the doctor tomorrow

If you have a fever for more than 5 days. If you cough and it is painful when you breathe. If your ears starts hurting.

Contact the doctor immediately

If you are drowsy and only wants to lie down and sleep. If you have trouble breathing.