COVID-19: overview

COVID-19 disease occurs as a result of an infection with the SARS-CoV‑2 coronavirus. People who become infected do not always have symptoms, so the virus can be passed on without being detected. Measures such as observing physical distance, following best hygiene practice, wearing a mask and getting vaccinated can help prevent infection and serious illness.

At a glance

  • Many people have now acquired a basic immunity to SARS-CoV‑2 due to infection, illness or vaccination.
  • The protection that is built up from having an infection reduces within a few months. For this reason, 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. Infection control measures have a role to play in this regard.

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

An older woman with a surgical mask

What is COVID-19?

COVID-19 is the abbreviated form of coronavirus disease 2019.

This disease 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 have to be hospitalized or even die as a result. The cause of death is usually lung or multiple organ failure.

Older people and people with pre-existing conditions are particularly at risk of becoming seriously ill with COVID-19. However, severe COVID-19 infections are also possible in young and otherwise healthy people.

What are infectious diseases?

The video below looks at when doctors talk about an infectious disease, which pathogens trigger infectious diseases, and how they are transmitted.

This and other videos can also be found on YouTube

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What are the symptoms of COVID-19?

For most people infected, the first symptoms of a SARS-CoV‑2 infection appear 1 to 10 days (around 3 days on average) following infection. However, not everyone shows signs of the disease, and some people have no symptoms at all.

Bei COVID-19 treten erste Symptome im Durchschnitt circa drei Tage nach der Ansteckung auf.

Common symptoms are:

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

These may be accompanied by other symptoms, such as shortness of breath, dyspnea (breathing difficulties), 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. It is important to always phone a medical practice before attending in person. Outside of consulting hours, you can contact the non-emergency medical assistance service by phoning 116117.

Important: If a rapid antigen test or PCR test detects that you have a COVID-19 infection, your local health authority will require you to self-isolate at home. Quarantine, i.e., reduced social contact and daily rapid antigen (self-)tests, is urgently advised for any close contacts who are at an increased risk of infection. 

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).

The latest information about the duration of self-isolation and quarantine periods is provided by the Robert Koch Institute (RKI) on its website.

Floating virus particles

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

The virus that causes COVID-19 is called SARS-CoV‑2 because 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. Particularly in enclosed, poorly ventilated places with no fresh air coming in, aerosols can stay floating in the air for longer periods and over long distances 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 also relatively unlikely, as 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. 

Based on current knowledge, breast milk is not a source of transmission. 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.

Time of exposure and incubation period

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: It is possible for people to contract SARS-CoV-2 without developing any symptoms. They can then pass on the virus to other people. However, this type of transmission is likely to play a less significant role.

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. The Omicron variant 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. They can then pass on the disease to others.

To prevent the spread of the disease, it is advisable to continue to observe infection control measures, such as physical distancing and wearing a mask.

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

Which factors increase the likelihood of developing a severe form of COVID-19?

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.

People with a weakened immune system also have a higher risk of developing a severe form of the disease. This can be caused, for example, by:

  • taking certain medication
  • a disease that impacts the immune system directly, such as cancer
  • a stem cell or organ transplant

Certain pre-existing conditions also increase the risk of becoming seriously ill with COVID‑19:

People who are obese, smokers and those with Down syndrome are also more likely to develop a severe form of COVID‑19.

In general, men are more likely than women to become seriously ill with the virus. 

The risk of severe illness is also elevated among pregnant women.

How does COVID-19 progress?

The progression of COVID-19 differs between individuals, depending on how effective the body’s immune system is against the virus. It ranges from mild to extremely severe. Long-term consequences are sometimes possible. In rare cases, the disease is fatal. Most people who have died from a SARS-CoV‑2 infection were over 70 years old.

Mild to moderate forms

Most 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 from the second week of the illness. Another possible complication is pneumonia. At this stage not enough oxygen is entering the bloodstream. Some of these people require hospital treatment, sometimes even with ventilators or other organ replacement therapies in an intensive care unit.

Treatment can be more complicated for people with additional bacterial or fungal infections as well as increased blood clotting. 

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.


Complications are also possible, for example, if the SARS-CoV‑2 infection causes pneumonia or if inflammatory processes in the body activate blood clotting. If an excessive immune response is activated throughout the body, this can also damage the lungs and cause severe respiratory problems.

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 that requires intensive care.  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. If symptoms caused by a COVID-19 infection persist beyond 12 weeks, medical professionals refer to this as post COVID‑19 condition or post 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 stamina, 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 non-restorative 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 COVID, its symptoms, outlook and treatment, 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 airborne droplets and breathing in aerosols.

This is why the “AHA+L” rules, i.e., hands, face, space and ventilation rules, help people avoid a SARS-CoV‑2 infection. (Self-)testing is also useful in certain situations. Another important measure is to get vaccinated against COVID-19. The coronavirus alert app helps users to keep track of daily contact with people who are at risk.

COVID-19 can be avoided by observing the rules on distancing and hygiene, wearing a mask over the mouth and nose, ventilating on a regular basis, (self-)testing, getting vaccinated and using the coronavirus alert app.

Observing the hands, face, space and ventilation rules

  • Keep your distance – greater distance between people means that viral droplets are more likely to fall onto the ground before they reach another person. A distance of at least 1.5 meters is recommended.
  • Maintain good hygiene – regular, thorough handwashing with soap and observing coughing and sneezing etiquette (turning away from others and coughing or sneezing into a tissue or into your elbow) are important measures.
  • Wearing a mask in everyday life – wearing a surgical mask or FFP2 mask catches virus-infected droplets so that fewer spread in the air. It is advisable to wear a mask when visiting the doctor, going shopping or using public transport, for example.
  • Ventilate regularly – ensuring that indoor areas have an adequate supply of fresh air is an effective way to remove virus-infected droplets from indoor air. It’s also important to open windows regularly to let fresh air in. The most effective type of ventilation is a cross-draft, created by opening windows opposite each other.

For more information about how the hands, face, space (AHA) and ventilation (+L) rules can help prevent a SARS-CoV‑2 infection, see – a website of the Federal Center for Health Education (“Bundeszentrale für gesundheitliche Aufklärung”, BZgA).


(Self-)tests can help reduce the risk of infection for yourself and others in certain situations, such as:

  • visiting loved ones in a hospital or nursing home
  • having contact with people in at-risk groups or people who work in healthcare settings
  • going to work in an office setting
  • attending a large celebration or public event
  • traveling by bus, railway or plane

Get vaccinated

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

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 swab sample from the back of the nose and throat and sending it to a laboratory for analysis.

How is COVID-19 treated?

Experts have developed recommendations for the treatment of COVID‑19. These recommendations are updated regularly and made available to doctors.

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
  • 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 recommended for COVID-19

Dexamethasone is an anti-inflammatory drug that is used for people with a 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 baricitinib (Olumiant) 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 for people who:

  • have an increased risk of developing a severe form of the disease or for whom immunization or full immunization is not recommended
  • are likely not to respond well to immunization – for example, because of a pre-existing condition or because they are receiving medical treatment that weakens their immune system

The approved active agents nirmatrelvir/ritonavir (Paxlovid) can be administered within the first 5 days of the onset of symptoms or the suspected time of infection. The active agent remdesivir can be administered within the first 7 days.

In Germany, doctors can also prescribe the antiviral drug molnupiravir (Lagevrio) for up to 5 days after the start of symptoms. It can be used in this country despite not having EU approval. 

Use of the antibodies sotrovimab (Xevudy) or tixagevimab/cilgavimab (Evusheld) may be beneficial in some situations. They bind to certain parts of the SARS-CoV-2 virus, preventing it from penetrating into the body’s cells. Their effectiveness depends on which virus variant has caused the infection. 

Important: The same rule applies to all antiviral substances – the earlier they are administered, the more likely they are to be effective.

Treatment with other medication

Under certain circumstances, another anti-inflammatory drug called anakinra (Kineret) is used in addition to dexamethasone to treat people in hospital who have developed 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).

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