COVID-19: overview

The respiratory disease COVID-19 is caused by an infection with the SARS-CoV-2 coronavirus. As well as the lungs, it can also affect other organ systems. People infected with the virus do not always have symptoms, so the virus can be passed on without being detected. Preventive measures must be followed since it can be severe or even fatal. These include following the rules on physical distancing and hygiene, wearing masks on an everyday basis and getting vaccinated.

At a glance

  • Because of infection, illness or a vaccination, many people have now acquired a basic immunity to SARS-CoV-2.
  • The immunity provided by these declines after a few months. So it is recommended that people top up their immunity with a booster vaccine.
  • People who have not been immunized can still be infected and become severely ill. People who have been vaccinated can also become infected. However they are far less likely to develop the severe form of the disease.
  • Older people and people with pre-existing conditions are particularly at risk of developing the severe form of the disease.
  • The numbers of those infected with the disease need to be as low as possible to allow those with the severe form to receive the best possible care. So the infection control measures should continue to be observed.

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

COVID-19: Older woman looking out of the window. She is wearing a mask over her mouth and nose.

What is COVID-19?

COVID-19 is the abbreviated form of “Corona Virus Disease 2019”. It is caused by the SARS-CoV-2 coronavirus which has spread very rapidly around the world since the end of 2019.

People who are infected do not always exhibit symptoms. But some become so ill that they die from it. Older people and people with pre-existing conditions are particularly at risk. COVID-19 can still be fatal in young and otherwise healthy people.

With COVID-19 the cause of death is usually lung or multiple organ failure. To prevent this from happening, doctors have to treat many patients with the severe form of the disease with ventilators or other organ replacement therapies in intensive care wards.

The number of people with the disease at any one time needs to be kept low to ensure that the healthcare system can provide this type of treatment to as many people who need it as possible. So all citizens need to follow the latest rules on physical distancing and hygiene, wear a mask during everyday life, restrict contacts, and get vaccinated.

More detailed information on how to avoid being infected with SARS-CoV-2 and prevent severe cases of COVID-19 is provided in the prevention section.

What are the symptoms of COVID-19?

In most cases, the first symptoms of a SARS-CoV-2 infection appear 1 to 10 days (around 3 to 6 days on average) following infection. However, those who have been infected don’t always show signs of the disease, and some have no symptoms at all.

In COVID-19 the first symptoms usually appear 1 to 10 days (around 3 to 6 days on average) following infection.

Common symptoms are:

  • coughing
  • high temperature
  • rhinitis (sneezing, itchiness and a blocked or runny nose)
  • lost or changed sense of smell and taste

These may be accompanied by other symptoms, such as shortness of breath, dyspnea (breathing difficulties), sore throat, headaches and joint pain, abdominal pain, nausea, vomiting, diarrhea, loss of appetite, weight loss, skin rash, conjunctivitis, lymphedema (lymph node swelling), drowsiness or impaired consciousness.

Children and adolescents are more likely than adults to have no symptoms at all or only mild symptoms, and are more likely to have gastrointestinal problems.

Most newborns whose mothers tested positive for SARS-CoV-2 during pregnancy do not have any symptoms.

What should people do if they have symptoms?

Stay at home and follow the rules on physical distancing and hygiene. Phone your family doctor for advice on what to do next. Never attend a medical practice in person without telephoning first.

Important: If there is reason to suspect that you might have COVID-19, or have tested positive for SARS-CoV-2, you should not leave your home anymore. If you have the disease the local health authority will require you to self-isolate at home. Your contacts may have to go into quarantine.

For answers to frequently asked questions regarding quarantine and more information on self-isolation at home, visit the websites of the Federal Center for Health Education (BZgA).

Where does SARS-CoV-2 come from and how is it transmitted?

The virus that causes COVID-19 is referred to as SARS-CoV-2 as it is related to the virus responsible for SARS (severe acute respiratory syndrome). 

SARS-CoV-2 is believed to have mutated from very similar coronaviruses in wild animals. At the current state of knowledge the first infections took place at a food market in the Chinese city of Wuhan where wild animals were also on sale.

Routes of transmission

SARS-CoV-2 is spread by larger droplet (airborne) transmission and by microdroplets suspended in the air (aerosols).

Infected people carry droplets containing the virus in their noses and mouths which are spread in the air when they talk, sneeze or cough. If these droplets come into contact with the mucous membranes in other peoples’ noses, mouths or eyes they may become infected with the virus. If the droplets condense on people’s hands and they then touch their mouths with their hand, the virus may be transferred to the mucous membranes (“transferred by touch”).

Aerosols are created by people when they breathe or speak, but even more when they shout loudly, sing or engage in sports activities. Aerosols can stay floating in the air for longer periods and over long distances, particularly in enclosed, poorly ventilated places with no fresh air coming in, and accumulate. This increases the likelihood of infection. Infection is unlikely outdoors, however, as long as people keep the recommended distance.

Infection via contact with surfaces contaminated with the virus is relatively unlikely since SARS-CoV-2 only survives short periods in the environment. However transmission cannot be ruled out, particularly where there are infected people in the immediate vicinity. 

Investigations are still being conducted into whether SARS-CoV-2 is transmitted via breast milk. The data currently available suggests that this is not the case. Breastfeeding women can continue to breastfeed their baby after becoming infected. However it is advisable to follow hygiene measures as far as possible whilst breastfeeding to avoid the risk of infection via droplets or aerosols.

Infection with virus variants

There are several mutated forms of the SARS-CoV-2 virus that spread faster and are more transmissible than the original virus. For this reason, they are referred to as variants of concern. Omicron is now the dominant strain in Germany.

Under certain circumstances it is also possible that people who have already recovered from an infection with SARS-CoV-2 or are vaccinated against COVID-19 could be infected again with one of these new variants. 

However the risk of transmitting the virus to other people or becoming seriously ill is far lower for people who have been vaccinated. To avoid passing on the virus unnoticed, the Standing Committee on Vaccination in Germany (Ständige Impfkommission – STIKO) recommends people follow infection control measures and get their first, second or booster shots.

Further information on the virus variants in Germany can be found on the Robert Koch Institute website.

What are the factors that favor COVID-19 and severe forms of the disease?

People infected with SARS-CoV-2 can transmit the virus to others 1 to 2 days before they experience any symptoms. The risk is greatest around the onset of symptoms.

How long someone stays infectious depends on the form the disease takes. Most people are no longer infectious after 10 days but it can take longer in some cases.

Important: People can also be infected without developing any symptoms. They can still sometimes be contagious to other people.

Who is particularly at risk?

Older people are more at risk of a severe form of the disease because the body’s immune defenses are weakened in later life. The risk increases from the age of about 50 to 60.

Smokers and people who are obese, pregnant women and people with Down’s syndrome are also more likely to have the severe form of COVID-19.

People with the following pre-existing conditions have a higher risk to develop the severe form of the disease, too:

How does COVID-19 progress?

The progression of COVID-19 differs between individuals, depending on how effective the body’s immune defenses are against the virus. It ranges from mild to extremely severe. In some cases, the disease is fatal. Long-term consequences are also possible.

Mild to moderate forms

Around 80% of recorded SARS-CoV-2 infections are mild to moderate. People can usually recover at home. 

Severe symptoms

The symptoms get worse in some infected people, often not until the second week of the illness. At this stage not enough oxygen is entering the bloodstream. Some of these people require hospital treatment, sometimes even in an intensive care unit and on a ventilator.

Treatment can be more complicated for people with additional bacterial or fungal infections as well as increased blood clotting. Pneumonia is a potential complication.

The likelihood of contracting a severe form of COVID-19 during pregnancy is low, but it is still higher than in women who are not pregnant. Moreover, pregnant women who have a bad case of COVID-19 are at greater risk of pre-eclampsia and premature birth than pregnant women with a mild form of the disease.

Children also rarely experience a severe form of the disease. However the risk is higher in infants and young children as well as children with pre-existing conditions.


Infection with the SARS-CoV-2 coronavirus can be fatal. Around 2 percent of people with a confirmed infection have died of it. Those affected were mostly over 70 years of age.

Important: Young people and people with no pre-existing conditions can still die of COVID-19.


Complications are also possible, for example when inflammatory processes in the body activate blood clotting. If an excessive defense response is activated throughout the body this can also damage the lungs and cause severe respiratory problems.

Generally, a high fever in the first trimester can also increase the risk of complications in pregnant women. Since pregnancy and COVID-19 both increase the risk of blood clots, preventive measures are advisable in some cases.

Some children develop pediatric inflammatory multi-system syndrome (PIMS) after recovering from an infection with SARS-CoV-2. This is a rare but often serious complication of the disease. PIMS is characterized by inflammation throughout the body, which can cause damage to various organs. A similar inflammatory syndrome may also occur in adults, but this is even rarer than in children.

Long-term consequences

People who become ill with COVID-19 can continue to have health problems for weeks or even months after the acute SARS-CoV-2 infection has resolved. This is usually referred to as “long-COVID”. Healthcare professionals also refer to symptoms that persist for a long time following a COVID-19 infection as post COVID-19 condition or post COVID for short.

Based on the latest findings, it is estimated that overall up to 20 in 100 adults develop long-COVID. The probability that health problems will remain over the long term is greater when the COVID-19 infection is severe. But long-term consequences are also possible even when the illness is mild or moderate. Here, the symptoms can occur singly or in combination.

The symptoms commonly described in association with long-COVID include fatigue and loss of endurance, shortness of breath and concentration and memory deficits, also referred to as “brain fog”.

It can also cause symptoms such as muscle weakness and muscle pain, sleep disorders (insomnia) and unrestorative sleep, depressive symptoms and excessive anxiety. Some people find that their lung function deteriorates or that their liver, kidney or heart functions are impaired.

To find out more about what is classed as long-COVID, what the signs are, how long-COVID progresses and how it is treated, how it can be prevented, read the article discussing long-COVID.

How can infection with COVID-19 be prevented?

COVID-19 is primarily spread by coming into direct contact with droplets (airborne) and breathing in aerosols.

That’s why restricting contact, following the hands, face, space (“AHA”) and ventilation (+L) rules, i.e. the rules on physical distancing and hygiene, wearing masks on an everyday basis and regular ventilation help to prevent infection with the SARS-CoV-2 coronavirus. Another important measure is to get vaccinated and get a booster vaccination when invited and protect against COVID-19 that way. Using the Corona alert app can also help.

COVID-19 can be prevented by restricting contact, physical distancing, following rules on hygiene, wearing a full face mask, regular ventilation, vaccination.

Restricting contacts

This involves restricting social contacts to the smallest possible specific group of people and avoiding large gatherings of people, particularly indoors. This helps to prevent mass infections and to keep the number of severe cases of COVID-19 and deaths as low as possible. So when infection rates are high people need to restrict contact with other people who do not live in the same household with them. The priority should be on protecting older people and people with pre-existing conditions by following the rules on visits to hospitals or older people’s care homes.

Following the rules on physical distancing

As far as possible, people should maintain a minimum distance of 1.5 meters away from other people at all times and in all places. Physical distancing can help people to protect themselves and others against infection at the workplace, whilst shopping or in people’s leisure time. That’s because greater distance between people increases the likelihood of the viral droplets falling to the ground before they reach another person. People should also avoid shaking hands or hugging.

Dozens of virions of the species SARS-CoV-2.

Following the rules on hygiene

People should wash their hands with soap regularly and thoroughly; for example when they are in the office or coming home from work or shopping. Follow coughing and sneezing etiquette: turn away from other people and sneeze or cough into a tissue or into your elbow. This stops the virus droplets from scattering over a wide area. Tissues should be disposed of in trash cans with a lid.

Wearing a mask on an everyday basis

Wearing a medical mask, i.e. a surgical mask or FFP2 mask catches virus droplets so fewer spread in the air. This protects both the wearers and those around them. Even people who don’t feel ill can spread the virus. Wearing a mask is most effective when everyone present wears a mask continuously when they come into contact (collective protection). Visors in front of the face, in contrast, can only catch large droplets that hit their screens directly. They are no substitute for a medical mask.

Further information on the various types of masks, when to use them and how to use them correctly is provided on the website of the Robert Koch Institute in the section on “Infection Protection Measures” and the website of the Federal Institute for Drugs and Medical Devices as well as

Regular ventilation

Indoor areas should have an adequate supply of fresh air. This allows droplets of active virus to be removed from the air in the room. It is important to ensure regular ventilation, particularly if it is not possible to avoid having several people in the room. Depending on the temperature outdoors, windows should regularly be left wide open for at least 10 to 15 minutes. If it is very cold outside, 5 minutes is often enough. Up to 30 minutes is advisable on hot days. Ideally windows opposite each other should be opened at the same time to allow a more effective cross-draft. 

Get vaccinated

Five vaccinations protecting against COVID-19 have been approved in Germany and the European Union: Comirnaty (BioNTech/Pfizer), Spikevax (Moderna), Vaxzevria (AstraZeneca), COVID-19 Vaccine Janssen (Janssen Cilag International/Johnson & Johnson) and Nuvaxovid (Novavax). 

Anyone from the age of 5 upwards can now be vaccinated. The German Standing Committee on Vaccination (Ständige Impfkommission, STIKO) recommends vaccination against COVID-19 for all people aged 12 or above including pregnant women, breastfeeding mothers and women trying for a baby.

In the 5 to 11 age group, STIKO recommends vaccination only for children with pre-existing conditions and children who come into close contact with people in at-risk groups. These include people taking medication that weakens the immune system, for example. It is currently not generally recommended for 5 to 11-year-olds with no pre-existing conditions. However a COVID-19 vaccination can be given after consultation with a doctor, if an individual requests it.

STIKO also recommends that people aged over 12 who have already been vaccinated should boost their protection. People aged 18 years and above should have their booster as recommended from 3 months after their primary immunization; children and adolescents aged 12 to 17 after 3 to 6 months.

All of the vaccines approved so far are highly effective and provide good protection against severe COVID-19 disease.

All of the vaccines approved so far are highly effective and provide good protection against severe COVID-19 disease. Serious side effects are very rare.

The available vaccines can also be used to protect oneself against the virus variants which are currently spreading widely, providing the recommended number of vaccine doses are taken that are required to achieve full protection.

Anyone who is vaccinated against COVID-19 can have this recorded digitally as well as entered in the yellow vaccination pass. The article on the EU-wide Digital COVID Certificate explains how this works.

The COVID-19 vaccination article explains what the vaccines do, how effective and safe they are, and for which age groups which vaccines may be used.

The website of the Robert Koch Institute provides answers to frequently asked questions on COVID-19 and vaccinations.

The recommendations published by the Standing Committee on Vaccination (Ständige Impfkommission) include more detailed information about vaccination against COVID-19.

Use the Corona alert app

The Corona alert app helps to record everyday contact with people at risk and to notify the user of these. It records contacts from the last 14 days. If someone has close contact with a person who (later on) tests positive, and has therefore been exposed to a high risk of infection, an alert in the form of an “increased risk” status notification appears on their device. If they have not had any contacts with at-risk persons, or contact was for a short period only or at a long distance, a green “low risk” status notification appears.

If “low risk” is displayed, no special measures are required. However it is recommended that people continue to follow the physical distancing and hygiene rules. If the app displays “increased risk”, however, it is important for the person to take certain measures regardless of whether they have been vaccinated or have recovered. These primarily include:

  • going home and staying there
  • contacting the family doctor if symptoms occur
  • getting tested
  • self-isolating if they test positive
  • sharing the test result via the app

Further information on what to do if a red alert appears on the app is available from the Robert Koch Institute at

The website of the Robert Koch Institute provides more questions and answers on how the Corona alert app works and how to use it.

How is COVID-19 diagnosed?

Infection with SARS-CoV-2 needs to be proven before a diagnosis of COVID-19 can be given. Doctors do this by taking a nose or throat swab sample and sending it to a laboratory for analysis.

In addition to the PCR laboratory tests, rapid lateral flow tests (rapid antigen tests) are used to provide on-site proof of a SARS-CoV-2 infection. They provide a result more rapidly than the laboratory tests. Anyone who has a positive rapid test result should have it confirmed with a follow-up laboratory test. The same applies to the rapid self tests that can be administered at home.

The test result is positive if viral material is detected in the sample. If this happens it’s important to list all contacts who may have become infected. Contacts are all people with whom they have been in close contact since 2 days before the start of the disease.

Examples of close contact with an infected person and an increased risk of infection include:

  • talking to someone without a mask at a distance of less than 1.5 m
  • coming into direct contact with droplets, for example by being coughed on, sneezed on or kissed
  • spending more than 10 minutes in poorly ventilated indoor areas

Important: All citizens can take at least one rapid test a week for free.

Frequently asked questions and answers on the rapid tests and self-administered tests such as how to get them and when they should be used are provided on the website of the Federal Ministry of Health and the Federal Center for Health Education

Detailed information on how to use the rapid self tests is provided by the Robert Koch Institute.

When is a test recommended? 

The Robert Koch Institute recommends a test for all close contacts of a person with a proven SARS-CoV-2 infection, regardless of whether there are any symptoms. Anyone with symptoms should contact a doctor. This is particularly the case if: 

  • they have respiratory problems due to acute bronchitis or pneumonia, shortness of breath or high temperature
  • they have an acute loss of their sense of smell or taste
  • there are unexplained pathological symptoms and close contact with a person with a confirmed SARS-CoV-2 infection
  • their health has deteriorated combined with unexplained COVID-19 symptoms

A test is also advisable for people with mild or severe acute respiratory problems who also, for example, meet one of the following criteria:

  • membership of an at-risk group or employment in care setting, medical practice or hospital
  • contact with infected people in their household
  • continued close contact with lots of people or at-risk patients

The website of the Robert Koch Institute provides detailed information on diagnosis of SARS-CoV-2.

How is COVID-19 treated?

Any treatment of COVID-19 focuses on measures that reduce the primary symptoms and problems.

Depending on how severe the illness is, these include, for example:

  • bringing down the fever
  • administering oxygen
  • restoring the balance of fluid
  • administering antibiotics if there are also bacterial infections
  • monitoring of relevant underlying conditions 

Treatment with medication may also be initiated to combat the virus itself or the inflammation caused by the virus. The exact treatment used depends on the stage of the disease and the individual’s risk of developing the severe form of the disease. Getting the medication right and assessing the risk factors are crucial here. That’s because early antiviral therapy is advisable in some cases, even where people are infected but have no symptoms or only have a mild form of the disease.

People who need hospital treatment for COVID-19 pneumonia may also need oxygen or mechanical ventilation depending on the severity of the disease. Treatment in an intensive care unit, where doctors can provide life support or treatment for complications, may also be required.

There are currently a number of drugs approved for COVID-19 in the European Union. Others are still being reviewed by the authorities but are permitted for compassionate use in exceptional cases based on recommendations in medical guidelines.

Drugs approved for COVID-19

Dexamethasone is an anti-inflammatory drug that is always used in people with the severe or critical form of the disease who need oxygen or are already on a ventilator because of COVID-19 pneumonia. Other anti-inflammatories such as tocilizumab (RoActemra) and anakinra (Kineret) can be used in addition to dexamethasone if the condition continues to deteriorate.

Treatment with antiviral medication is especially important at the early stages of the infection, particularly in people who are at a high risk of developing the severe form of the disease. Thus the active agent remdesivir can be administered within the first 7 days and the active agent nirmatrelvir/ritonavir (Paxlovid) within the first 5 days after the onset of symptoms.

The antibodies casirivimab/imdevimab (Ronapreve) and sotrovimab (Xevudy) are also intended for treatment within the first 5 to 7 days of the onset of symptoms. They bind to certain parts of the SARS-CoV-2 virus, preventing it from penetrating into the body’s cells. 

Treatment with other medication

Doctors in Germany can now also prescribe the antiviral drug molnupiravir (Lagevrio). This can be used in Germany despite not having EU approval. It can also be considered for treatment in the early stages of the disease and if there is a high risk of developing the severe form. Doctors can also administer the drug up to 5 days after the onset of symptoms.

Under certain circumstances, administration of baricitinib (Olumiant), another anti-inflammatory drug, in addition to dexamethasone is recommended for the treatment of people with COVID-19 pneumonia.

Patients who are at an increased risk of thrombosis should also be given preventive treatment (prophylaxis) appropriate to their risk profile, or treatment with anticoagulant drugs such as heparin, provided there are no contraindications.

In cooperation with the Robert Koch Institute (RKI). As at:

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