Flu (Influenza)

Many people talk about the flu when they have a common cold. But the two infections progress in very different ways. While a cold develops slowly, the flu begins quickly and fiercely. Read how flu can be prevented and what the treatment options are.

At a glance

  • Many people talk about the flu when they have a common cold, but the two infections progress in very different ways.
  • While a cold develops slowly, flu viruses strike quickly and fiercely.
  • Typical flu symptoms are headaches, high temperature, muscle and joint pain throughout the whole body.
  • Flu is caused by being infected by viruses.
  • Regular hand washing can prevent an infection.

Note: The information in this article cannot and should not replace a medical consultation and must not be used for self-diagnosis or treatment.

Influenza: young woman sitting in a chair. Her upper body is wrapped up in a blanket up to her chin. The woman is holding a handkerchief to her nose with one hand.

What is flu?

When a common cold emerges, many people talk about the flu, but the two illnesses progress in very different ways. A cold can be distinguished from the flu through their typical ill effects.

Colds occur far more frequently than the flu. But the main difference is that a cold develops slowly, whereas the flu begins quickly and fiercely, including in people who are usually healthy. So someone with flu quickly feels very ill. 

The common cold develops slowly and passes quickly. Influenza starts quickly and severely and lasts longer.

A cold usually progresses harmlessly. The ill effects often fade away within a week, whether or not they have been treated.

In contrast, with the flu it takes a while before the person is fully recovered. Sometimes it is also a good idea to consult a doctor.

Nevertheless, what the common cold and the flu have in common is that it is the symptoms which are usually treated. As yet, even against flu viruses, there are only medications that can, at best, slightly shorten the duration of the illness.

What are the symptoms of the flu?

Genuine flu is also known as influenza. Many of its symptoms resemble those of the common cold: fever, achy head and limbs, and a blocked or runny nose may occur.

However, the flu affects the entire body, not just the airways. Flu viruses strike quickly and fiercely. Most really nasty ill effects usually fade away a lot within a week. But fatigue and coughing often last longer.

Typical flu symptoms include:

  • fever between 38 °C and 40 °C or more
  • muscle and joint pain all over the body (myalgia and arthralgia)
  • headaches
  • extreme fatigue and a very ill feeling
  • dry coughing without phlegm
  • blocked and/or runny nose
  • loss of appetite
  • extreme tiredness

When flu is suspected, it is a good idea to consult a doctor. This particularly applies to people with pre-existing conditions for whom there is a greater risk of complications, for example due to chronic lung disease or diabetes. If sufferers have contact with anyone who is at risk, it is advisable to talk to a doctor about it.

Typical symptoms of influenza include high temperature (from 38°C to 40°C or higher), headache, muscle pain, joint pain, severe fatigue and lassitude, dry cough, rhinitis (sneezing, itchiness and a blocked or runny nose), loss of appetite.

What causes flu?

Flu is caused by viruses. Viruses are tiny, microscopic germs even smaller than bacteria. Once they get into the body, viruses multiply quickly. To combat a virus infection, the human body's defense system generates antibodies – but it needs time to do so.

There are hundreds of flu viruses that are collated into groups. Virus groups Influenza A and Influenza B are the most dangerous.
Someone who has had the flu develops an immunity to the specific flu virus that caused their illness. However, nobody is permanently protected after suffering from flu: the viruses are constantly changing, so completely new types of virus can emerge from year to year.

What causes osteoarthritis?

The video below explains the differences between a cold and a flu: the different triggers, symptoms, treatment options, and possibilities of a more severe course.

This and other videos can also be found on YouTube

Watch now

The privacy policy indicated there applies.

How does flu develop?

The flu is very often followed by an inflammation of the sinuses (sinusitis). When sinusitis occurs, the cavities around the nose are filled with an infectious fluid. Frequent complaints include headaches and a blocked nose. 

In babies and infants, infections of the air ways often lead to an inflammation of the middle ear.

The flu rarely develops into something serious. Complications such as pneumonia are rare. This is primarily a risk for people with a weaker immune system. They are usually babies and infants, people with lung or immune diseases, and people over the age of 60. If the flu becomes very serious, it may be life-threatening.

How can flu be prevented?

Cold and flu viruses are spread by airborne infection. A sufferer scatters droplets containing the virus when coughing and sneezing. And when cleaning one's nose, viruses can get from the handkerchief to the hands, and from there reach other people or objects.

An example: many people touch the doorknobs and handles on public transport, so the viruses can easily be transmitted from person to person. Direct contact by shaking hands or hugging can also spread cold and flu viruses.

To protect oneself and others from the illness, the most effective course of action is to prevent spreading these viruses. So, for example, it is important to wash one's hands thoroughly and to put used paper tissues straight into the trash.

Even when the flu is fading away, sufferers remain infectious for up to another week. So during this time it is advisable to avoid social contact if possible and, for example, to work from home.

A flu vaccine can also provide protection. However, because flu viruses are constantly changing (mutating), an annual booster is required to ensure proper immunization protection.

For further information, for instance on how much protection a vaccine provides against flu, visit gesundheitsinformation.de.

How is flu treated?

Many people opt for homespun remedies such as chicken broth and herbal teas to alleviate the effects of flu. It is also felt that one should drink plenty. However, it is not scientifically proven that these measures help fight flu. So there is no need to use these homespun remedies or to drink much more than one wants to.

Important: There are many commercially available products such as vitamin products and inhalation devices to combat colds, coughs and the flu. There is no convincing evidence that these speed up recovery, either.

Painkillers like paracetamol, acetylsalicylic acids (for example in aspirin) and ibuprofen can alleviate pain and reduce fever.

Note: the agent acetylsalicylic acid (ASA) is not suitable for children and adolescents. It can cause a rare but dangerous side-effect: Reye syndrome – a disease that particularly affects the brain and liver and which is life-threatening.

As well as the over-the-counter medicines mentioned, there are specific flu drugs. Oseltamivir (brand name Tamiflu), in particular, is used in Germany. Oseltamivir is only available on prescription and must be taken within 2 days from the start of the illness.

If the symptoms have been there for longer, the drug can no longer affect the progress of the flu. There is evidence that oseltamivir could shorten the duration by just under one day. However, it often causes nausea and vomiting.

Antibiotics cannot help with flu, as antibiotics only act against bacteria and not against viruses.

In cooperation with the Institute for Quality and Efficiency in Health Care (Institut für Qualität und Wirtschaftlichkeit im Gesundheitswesen) (IQWiG). As at:

Did you find this article helpful?