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COVID-19, cold, flu – symptoms at a glance

ICD codes: J06 J10 J11 U07.1 U07.2 What is the ICD Code?

The symptoms of infection with the SARS-CoV-2 coronavirus are similar to those of the common cold or flu. The conditions cannot be distinguished by these symptoms alone. Tests help provide clarification if an infection with one of these viruses is suspected. 

At a glance

  • COVID-19, flu, and the common cold are infectious diseases that primarily affect the airways and are usually triggered by various viruses.
  • Common symptoms of all three illnesses are sore throat, cough, and rhinitis (sneezing, itchiness and a blocked or runny nose). A high temperature is more likely to occur with flu and COVID-19 than with a common cold.
  • People with acute symptoms should recover at home until these have cleared up. More severe symptoms may require a visit to a family doctor.
  • COVID-19 and flu can become severe, and complications can develop. This is rarely the case with a common cold in otherwise healthy people.
  • Various hygiene measures reduce the risk of infection.
  • Vaccinations offer protection against severe flu and COVID-19 infections.

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

A man with a cold sitting at home.

Differences between COVID-19, flu and common cold

COVID-19, the common cold, and flu are infectious illnesses that primarily cause respiratory symptoms. All are usually triggered by viruses.

For example, the common cold is caused by rhinoviruses or RS (respiratory syncytial) viruses. Flu, meanwhile, is triggered by influenza viruses. COVID-19 is caused by an infection with the SARS-CoV‑2 coronavirus. 

The symptoms of COVID-19 are similar to those of flu or the common cold. As a result, it is impossible to distinguish between the illnesses based on symptoms alone. Rapid self-tests for COVID-19, flu or RSV may indicate that a person has been infected with one of these viruses. However, they cannot provide a reliable diagnosis. This requires a PCR test.

Rapid tests often only detect an infection if there is a large amount of virus present at the collection site, i.e., in the nose or throat. In other words, it is possible to have an infection but to have a negative test result. On the other hand, if a person has symptoms and the rapid test is positive, the result is usually correct. 

Important: Anyone who develops a high temperature, limb pain, cough, rhinitis (sneezing, itchiness and a blocked or runny nose) or other symptoms of a cold or flu should stay at home and avoid contact with other people. Stay at home for about 3 to 5 days until the symptoms have significantly improved. If you are at an increased risk of developing a severe infection or if you have more severe symptoms, contact your family doctor at an early stage.

What are the symptoms of COVID-19?

Typical symptoms of a COVID-19 infection are cough, rhinitis (sneezing, itchiness and a blocked or runny nose), sore throat, headache, and limb pain. A high temperature is more likely to occur with COVID-19 than with a simple cold.

Other possible symptoms include general weakness and shortness of breath that can reach the point of respiratory distress (difficulty breathing). More rarely, people may experience nausea, abdominal pain, diarrhea, conjunctivitis, skin rash, and swelling of the lymph nodes.

One unusual symptom that occurred early in the COVID-19 pandemic was an impaired sense of smell or taste. This symptom is much rare in more recent virus variants such as Omicron. An infection with Omicron often causes milder symptoms than an infection with earlier variants. Symptoms generally disappear within 1 to 2 weeks.

Important: In principle, the severity of the symptoms may vary widely from person to person. An infection with SARS-CoV-2 may also cause no symptoms. However, some cases are severe and lead to complications such as pneumonia. Those affected may develop lung or multiple organ failure and die of the illness. 

Long-term health effects may also be caused by an infection with the SARS-CoV-2 coronavirus. These are referred to as long COVID or post-COVID syndrome/condition. 

What are the signs of flu?

A sudden onset of the illness with a high temperature, cough, and sore throat, is typical with flu (influenza). It is usually also accompanied by headache and limb pain, as well as a severe feeling of discomfort.

Other possible symptoms are weakness, sweating, and rhinitis (sneezing, itchiness and a blocked or runny nose). Nausea, vomiting, and diarrhea occur more rarely.

The severity of a flu infection can vary widely between one person and the next. Only one third of people infected have the typical form of the condition with a high temperature. Another third have a milder form and the final third don’t develop any symptoms at all.

Flu generally lasts 5 to 7 days. However, coughing and a general feeling of weakness can persist for much longer. Flu can also sometimes cause severe symptoms and complications like pneumonia. Encephalitis (inflammation of the brain) or myocardial inflammation (inflammation of the heart muscle) can occur in rare cases. Middle ear infections may also develop in children.

Important: Older people often do not experience a high temperature with flu. However, they are at a far higher risk of a severe case than children, who typically experience a high temperature. Flu is often also more severe during pregnancy or when certain underlying illnesses are present.

What causes a flu outbreak?

A large number of people contract flu during an outbreak. In Germany, flu outbreaks typically occur during the colder half of the year, and may persist until May. One reason for this is that flu viruses can spread more easily at lower temperatures and in drier conditions. Following an infection, people temporarily have a certain degree of immunity against flu viruses. However, as flu viruses mutate and change very frequently, it is possible to become infected again soon after recovering from one infection.

During a flu outbreak, approximately 5% to 20% of the population is infected.

During a flu outbreak, approximately 5% to 20% of the population is infected. The outbreak may have “peaks”, when a particularly large number of people become infected and ill at the same time.

During particularly severe flu outbreaks, many people with severe cases may require intensive care treatment at the same time. This can temporarily place undue pressure on the healthcare system in affected regions.

And, if increasing numbers of cases of COVID-19 or other respiratory infections occur alongside a flu outbreak, this can cause a temporary escalation of the situation in hospitals and on intensive care wards. 

More detailed information about flu is provided on the website of the Federal Center for Health Education (Bundeszentrale für gesundheitliche Aufklärung, BZgA).

What are the signs of a common cold?

A common cold is often characterized by rhinitis (sneezing, itchiness and a blocked or runny nose), coughing, and occasionally a sore throat. High temperatures are less common in colds than in flu. Complications are rare.

Further information about the common cold is available from the Lung Information Service provided by the Helmholtz Center (Heimholtz Zentrum) in Munich.

How can people protect themselves against a common cold, the flu and COVID-19?

During the colder months of the year, people are more likely to contract the common cold, flu, and COVID-19. However, various simple measures can be taken to protect ourselves and others. These include:

  • regular ventilation of indoor spaces
  • regular, thorough handwashing
  • coughing and sneezing into the crook of the elbow or a tissue
  • reducing contact and recovering at home if symptoms are acute

Important: It can still be useful to wear a mask indoors – for example, if a person is unable to avoid contact with others despite having acute symptoms. People in at-risk groups can also protect themselves by wearing a mask. 

Simple hygiene measures and an up-to-date vaccine status offer the best protection against COVID-19 and flu.

Vaccination against COVID-19 and flu

Vaccinations are an important measure to take as protection against infectious diseases. The vaccines against COVID-19 and flu offer good protection against severe illness. However, it is still possible to become infected with the virus following vaccination. For this reason, it is advisable to continue taking precautions even after getting a vaccine. 

The Standing Committee on Vaccination in Germany (Ständige Impfkommission, STIKO) recommends that all people aged 18 and older should have basic immunity against COVID-19 as protection against the virus. Basic immunity is also recommended for some children and adolescents – for example, those with certain underlying illnesses. Annual booster vaccines are also recommended for various groups of people. These include people aged 60 and over, people with certain underlying illnesses, or who have an increased risk of infection due to their occupation.

Important: Basic immunity requires a minimum of three contacts with parts of the coronavirus. These may consist of doses of the COVID-19 vaccine or infections with the virus. To maximize basic immunity against the virus, at least one of the three contacts should be in the form of a vaccine.

STIKO also recommends annual vaccination for various groups of people to avoid as many severe flu infections as possible. These groups include all people aged 60 and older, people with underlying illnesses, those in the second or third trimester of pregnancy, and people who are at an increased risk of infection due to their occupation. 

Important: In addition, STIKO recommends a pneumococcal vaccine for all people aged 60 and over, people with certain underlying illnesses and children aged between 2 and 24 months. A single RSV vaccine is also recommended for anyone aged 75 or above. For people who live in a residential care facility or who have serious pre-existing diseases, vaccination can sometimes be advisable from the younger age of 60.

It is normally possible to receive more than one vaccine at the same appointment – for example, the COVID-19 and flu vaccines can be given together.

More detailed information about vaccination against COVID-19 is available on infektionsschutz.de – a website run by the Federal Center for Health Education (Bundeszentrale für gesundheitliche Aufklärung, BZgA).
The “Corona-Impfcheck” online vaccination checker tool allows you to check whether vaccination is currently recommended for you. 

impfen-info.de provides information about flu vaccines, pneumococcal vaccines and RSV vaccines.
The Grippe-Impfcheck and RSV-Impfcheck online flu and RSV vaccination checker tools can be used to check whether vaccination is recommended for you. 

The Robert Koch Institute (RKI) also answers various questions relating to vaccination against COVID-19, the flu vaccine, the pneumococcal vaccine and the RSV vaccine.

In cooperation with the Robert Koch Institute (RKI).

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