Flu Symptoms: Recognizing Real Influenza, Treatment and Vaccination

At a glance

What is it? A contagious respiratory illness caused by influenza viruses.
Not to be confused with A common cold, which is usually much milder.
Typical Sudden onset with high fever, body aches and severe exhaustion.
Best prevention The annual flu vaccination, ideally from October to mid-December.
Treatment Mostly easing symptoms; antiviral medicines only work early.
ICD-10 J11 (influenza / flu)

Contents

  1. What is the flu (influenza)?
  2. Flu symptoms: typical and sudden
  3. Flu or a cold? Telling them apart
  4. Treatment and the antiviral window
  5. The flu vaccination: who and when
  6. Avoiding infection
  7. When to see a doctor

What is the flu (influenza)?

The flu (influenza) is a contagious illness of the respiratory tract caused by influenza viruses. It occurs above all in winter in waves, the so-called flu season, which in Germany usually runs between December and April and often peaks in January and February.

Important: real flu is not the same as a common cold. It often runs much more severely and can cause serious complications, especially in older people, the chronically ill, pregnant women and very young children. It is transmitted above all through droplets when coughing, sneezing and talking, as well as via the hands.

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Flu symptoms: typical and sudden

Unlike a cold, real flu usually starts suddenly, often within a few hours. Typical flu symptoms are:

  • high fever, often with chills. More on this: Fever.
  • severe headache and body aches.
  • marked tiredness and weakness, which can often last for weeks.
  • a dry cough and a sore throat.
  • sometimes a runny nose, in children also nausea or vomiting.

Most healthy people recover within one to two weeks, and the main symptoms often ease after five to seven days. But cough and tiredness can linger longer.

Flu or a cold? Telling them apart

In everyday life, flu and a cold are often confused, but they are different illnesses with different pathogens. This table helps to classify them:

Real flu (influenza) Common cold
Onset usually sudden, within hours rather gradual, over days
Fever often high (over 38.5 degrees), with chills mild or no fever at all
Body aches often severe mild or none
Exhaustion marked, often for weeks rather mild
Runny nose and sneezing less in the foreground typical and pronounced
Cough often dry and distressing usually mild
Overall impression you feel really ill run down, but usually still functional

Scroll the table sideways →

The boundaries are blurred, and the two cannot always be told apart for certain. Other respiratory viruses such as the coronavirus can cause similar symptoms too, and here a test helps if in doubt. More on the topic: Respiratory infections.

Treatment and the antiviral window

In most healthy people, the flu heals on its own. The focus is on supporting the body:

  • rest, sleep and plenty to drink.
  • fever-reducing and pain-relieving medicines (for example with paracetamol or ibuprofen) for fever and body aches.
  • staying at home to recover and not to infect others.

Antiviral medicines and the window. There are antiviral medicines against the flu viruses themselves (for example oseltamivir). But they only work if started early, ideally within about 48 hours of the symptoms beginning. After that, the benefit drops sharply. They usually shorten the illness by only about a day and are not needed for everyone, being sensible above all for risk groups and severe courses. Whether such a medicine is an option is decided by a doctor. That is why, with an increased risk, it is worth getting in touch early.

Antibiotics do not help against the flu, since it is caused by viruses. They are only an option if a bacterial complication develops in addition, for example pneumonia.

The flu vaccination: who and when

The most important prevention is the annual flu vaccination. It has to be repeated every year, because the viruses change and protection wanes.

Who should be vaccinated? The vaccination is recommended, among others, for:

  • people aged 60 and over (for them there is a special, enhanced high-dose vaccine).
  • people with chronic illnesses (for example of the heart, lungs, kidneys or with diabetes), at any age.
  • pregnant women (from the second trimester, earlier with an increased risk).
  • residents and staff of care facilities, medical staff and people who are close contacts of risk groups.

Those who do not belong to these groups can also be vaccinated, ideally after checking who covers the cost.

When is the best time? Ideally from October to mid-December, that is before the flu season. Protection builds up over about ten to fourteen days. A later vaccination can still be worthwhile as long as the season is not yet over. More on this: Vaccinations.

Vaccination reminder

Think of the flu shot in good time every season.

The flu vaccination only works if it is done in time, and it has to be repeated every year. brite can remind you in good time each season and keeps your vaccinations and medicines in one place.

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Avoiding infection

Besides the vaccination, simple measures help to avoid infection:

  • wash your hands regularly and thoroughly.
  • cough and sneeze into the crook of your arm and keep your distance from people who are ill.
  • ventilate indoor rooms regularly during the flu season.
  • with your own symptoms, stay at home and avoid close contact.

When to see a doctor

See a doctor early if you belong to a risk group (for example older people, the chronically ill, pregnant women) and have flu symptoms, because then an antiviral medicine can be sensible and the window is short. You should also be seen if the symptoms do not get better after about a week or get worse.

Have these warning signs assessed at once Get medical help quickly or call the emergency number (112, in the US: 911) with shortness of breath or breathlessness, pain or pressure in the chest, bluish lips, confusion, or if you suddenly feel much worse after an initial improvement (this can point to an additional bacterial infection). In babies and small children, warning signs include fast or labored breathing, bluish skin, refusal to drink or unusual unresponsiveness. When in doubt, it is better to get help once too often.

Through the flu season with brite

Whether a vaccination date, fever-reducing medicines or your long-term medicines: brite helps you keep the overview.

  • Vaccination reminder: thinks of the annual flu shot in good time each season.
  • Intake reminders: for fever-reducing medicines or an antiviral medicine within the window.
  • Symptom diary: record fever and the course, helpful for your appointment.
  • Interaction check: in case new medicines are added to your long-term ones.
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Frequently asked questions

A sudden onset with high fever, chills, severe headache and body aches, marked tiredness, a dry cough and a sore throat. You usually feel really ill, unlike with a mild cold.

The flu usually starts suddenly and intensely, with high fever and severe body aches. A cold comes on more slowly, with a runny nose and a sore throat and usually without high fever. But the two cannot always be told apart for certain.

Most healthy people recover in one to two weeks, with the main symptoms often easing after five to seven days. Cough and tiredness can last longer. If the symptoms get worse or breathing problems are added, see a doctor.

They can help, but only work if started early, ideally within about 48 hours. They usually shorten the flu by only about a day and are mainly meant for risk groups and severe courses. The doctor decides.

No. The flu is caused by viruses, against which antibiotics do not work. They are only an option if a bacterial complication such as pneumonia develops in addition.

Ideally from October to mid-December, before the flu season. Protection builds up over about ten to fourteen days. A later vaccination can still be worthwhile. The vaccination has to be repeated every year.

The vaccination is recommended, among others, for people aged 60 and over, the chronically ill of any age, pregnant women, staff and residents of care facilities and medical staff. Those who do not belong to these groups can also be vaccinated.

With shortness of breath, chest pain, bluish lips, confusion or a sudden worsening after an initial improvement. In babies, also with fast breathing, bluish skin or refusal to drink. Then get help immediately.

Related topics

Fever Respiratory infections Vaccinations Common cold Pneumonia

Quellen

  1. Robert Koch-Institut (RKI): Ratgeber Influenza (saisonale Influenza). rki.de
  2. STIKO (Ständige Impfkommission am RKI): Empfehlungen zur Influenza-Impfung (Epidemiologisches Bulletin). rki.de
  3. RKI / Arbeitsgemeinschaft Influenza: Influenza-Surveillance und GrippeWeb. influenza.rki.de
  4. IQWiG / gesundheitsinformation.de: Grippe (Influenza). gesundheitsinformation.de
  5. BZgA: infektionsschutz.de, Grippe und Grippeimpfung. infektionsschutz.de
Important note: This article is for general information and does not replace medical advice, diagnosis or treatment. Recommendations on the flu vaccination can change every year; the current recommendations of the RKI and STIKO are decisive. With shortness of breath, chest pain or a sudden worsening, call the emergency number (112, in the US: 911). Last updated: June 2026.