COVID-19: overview

The pulmonary disorder COVID-19 is caused by an infection with the SARS-CoV-2 coronavirus. 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 a full face mask and getting vaccinated.

At a glance

  • Because of illness or a vaccination, many people have now acquired a basic immunity to the SARS-CoV-2 coronavirus.
  • It’s not yet clear how long immunity lasts after recovering from the disease.
  • People who have not been immunized can still be infected and contract the disease. This cannot be ruled out with people who have been vaccinated, either.
  • Some people may not have any of the symptoms such as a high temperature, but there are severe and fatal forms of the disease.
  • Older people and people with pre-existing conditions are particularly at risk.
  • 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 protection measures specified 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 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, full face masks and restricting contacts, and get vaccinated when invited.

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.

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

What are the symptoms of COVID-19?

The first symptoms appear 1 to 14 days (around 5 to 6 days on average) following infection. But people infected with SARS-CoV-2 don’t always show signs of the disease, and some do not feel any symptoms at all.

In COVID-19 the first symptoms appear 1 to 14 days (around 5 to 6 days on average) following infection.

Common symptoms of COVID-19 include:

  • 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, sore throat, headaches and joint pain, abdominal pain, nausea, vomiting, diarrhea, loss of appetite, weight loss, skin rash, conjunctivitis, lymphedema, drowsiness, 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.

Pregnant women who become infected with SARS-CoV-2 relatively rarely have high temperature and muscle pain. 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. The local health authority will then require you to self-isolate (quarantine at home).

For answers to frequently asked questions regarding self-isolation, visit the website 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). It is sometimes also called novel coronavirus.

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 had also been on sale.

Routes of transmission

SARS-CoV-2 is spread by 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 particularly when they shout loudly, sing or engage in intense sports activities. Aerosols can stay floating in the air for longer periods and over long distances, particularly in enclosed, unventilated places, making infection more likely. Infection is rare outdoors.

It is not yet clear whether SARS-CoV-2 is transmitted via breast milk. However the data currently available suggest that breast milk is not a source of transmission.

Infection via objects is relatively unlikely since SARS-CoV-2 only survives short periods in the environment. However transmission via surfaces contaminated with the virus cannot be ruled out, particularly where there are infected people in the immediate vicinity. Although viruses are found in the stools of people affected, it is unlikely that they are infectious. SARS-CoV-2 does not appear to be transmitted via pets.

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

The SARS-CoV-2 coronavirus is transmitted by person to person contact and is now present throughout the world. People become infectious 1 to 2 days before the first symptoms but the risk of infection is greatest one day before.

How long they stay infectious depends on the form the disease takes. The average time people remain infectious is 9 to 10 days, rising to 20 in some cases.

Important: People who do not (yet) have any symptoms can still infect others.

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 are also more likely to develop the severe form of the disease.

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

The website of the Robert Koch Institute provides answers to frequently asked questions on at-risk groups.

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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How does COVID-19 progress?

The course of the disease differs depending on how effective the body’s immune defenses are against the virus. It ranges from mild to extremely severe. COVID-19 can also sometimes be 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 recover at home. The disease is generally benign in most pregnant women with COVID-19.

Severe symptoms

The symptoms get worse around 7 to 10 days after catching the disease in around 14% of people. At this stage not enough oxygen is entering the bloodstream. Some of these patients require intensive medical care and mechanical ventilation.

Treatment is more complicated for people with additional fungal or bacterial 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 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.


Infection with the SARS-CoV-2 coronavirus can be fatal. Between 2 and 3 percent of people with a confirmed SARS-CoV-2 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 can arise, 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 may be advisable in some cases.

Long-term consequences

According to estimates, around 15 percent of people who become ill with COVID-19 still have persistent symptoms weeks or months after the acute infection fades away. When there are still symptoms 4 weeks later, or if there are additional symptoms, medical practitioners call this long COVID. If this occurs over a period of more than 12 weeks, it is referred to as post-COVID-19 syndrome.

The probability that health problems will remain over the long term is greater when the illness is severe. But there can be long-term consequences even when the illness is mild or moderate.

The symptoms commonly described include exhaustion and fatigue, breathlessness and loss of endurance, weak and aching muscles, sleep disorders, depression and anxiety. These can occur singly or in combination. Some people find that their lung function deteriorates or that their liver, kidney or heart functions are impaired.

How can infection with COVID-19 be prevented?

COVID-19 is primarily spread by direct droplet (airborne) transmission and aerosols.

That’s why restricting contact, following the rules on physical distancing and hygiene and wearing masks on an everyday basis help to prevent infection with the SARS-CoV-2 coronavirus. Regular ventilation and using the Corona alert app also help. Another important measure is to get vaccinated and protect against COVID-19 that way.

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

Restricting contact

This involves restricting social contacts and avoiding large gatherings of people. This helps to prevent mass infections and to keep the number of severe cases of COVID-19 and deaths as low as possible. So during an acute pandemic 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.

Physical distancing

As far as possible, people should maintain a minimum distance of 1.50 meters away from other people at all times and in all places. Physical distancing can provide protection 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.

Two women and a man sitting together at a large desk and working. They are all wearing a full face mask and are segregated by sheets of plexiglass.

Rules on hygiene

People should wash their hands with soap thoroughly and often; 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 hold a tissue in front of your face, or sneeze 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.

Full face mask

Wearing a full face mask (surgical mask) stops virus droplets spreading in the atmosphere. This protects both the wearers and those around them. Even people who don’t feel ill can spread the virus. However these surgical masks only act as a mechanical barrier against larger droplets and are not much help against aerosols. For this reason, “FFP2” masks are used for protection against aerosols in the healthcare sector. Visors, in contrast, can only catch the droplets that hit their screens directly. They are no substitute for a full face 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 (BfArM) 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 large numbers of people in the room. Windows should be left wide open for at least 10 to 15 minutes on average. Ideally windows opposite each other should be opened at the same time to allow a more effective cross-draft. Keeping the window (permanently) tilted is not very effective in crowded rooms.


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

Anyone from the age of 12 upwards can now be vaccinated. The Standing Committee on Vaccination in Germany (STIKO) does not currently recommend the vaccine for pregnant women who are healthy.

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.

Vaccines enable people to protect not only themselves but also other people who cannot be vaccinated because of certain pre-existing conditions or life circumstances.

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 fully vaccinated against COVID-19 can have this recorded digitally as well as entered into the yellow certificate of vaccination. 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.

Answers to frequently asked questions on COVID-19 and vaccinations are provided on the website of the Robert Koch Institute.

More detailed information on the COVID-19 vaccination approval process can be found in the recommendation published by the Standing Committee on Vaccination (Ständige Impfkommission – STIKO).

The COVID-Cube – an interactive decision-making tool provided by the German Network Health Competence e.V. – can help people to weigh up the pros and cons of the COVID-19 vaccination.

Corona alert app

The Corona alert app records all close contacts between smartphones via Bluetooth and stores them on the smartphone. Anyone who tests positive for SARS-CoV-2 can report this to the app. This information and contacts stored over the last 14 days are then uploaded to a server which automatically informs contacts of the potential risk. Notifications are made anonymously. The risk is shown as low or high depending on when the contact occurred and how long it lasted. People who receive a “high risk” alert and have symptoms should contact a medical practice or the local health authority. They may recommend taking a test.

The Corona alert app is designed to break the chain of infection and stem the spread of COVID-19. The more people use it, the more effective it is. The app can also be used to show digital evidence of test results and the vaccination status.

The website of the Robert Koch Institute provides answers to frequently asked questions on the Corona alert app.

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 must have it confirmed with a laboratory test. The same applies to the rapid self tests that can be bought and 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.

Important: Until October 11th, 2021, all citizens can take at least one rapid test a week for free. Anyone who has not been fully vaccinated or recovered by then and has to show evidence of a test must pay for it themselves. Exceptions include people who cannot be vaccinated for certain reasons or for whom no vaccination is generally recommended, such as children below the age of 12 and pregnant women.

Important 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 (BZgA). 

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.

People should also take a test if they meet one of the following criteria:

  • respiratory problems due to acute bronchitis or pneumonia, shortness of breath or high temperature
  • acute loss of the sense of smell or taste
  • unexplained pathological symptoms and close contact with a person with a confirmed SARS-CoV-2 infection
  • deterioration in health combined with unexplained COVID-19 symptoms

Important: Talking to someone for 10 minutes or more without a mask at a distance of less than 1.50 m, for example, or coming into direct contact with droplets from infected persons, for example by being coughed on, sneezed on or kissed, increase the risk of infection. Spending more than 30 minutes in poorly ventilated indoor areas can also increase the risk.

A test is also needed by people with mild or severe acute respiratory problems who also meet one of the following criteria:

  • membership of an at-risk group
  • employment in care setting, medical practice or hospital
  • following events with more than 10 persons in enclosed, poorly ventilated spaces and inadequate compliance with hands, face, space (AHA) and ventilation (+L) rules
  • contact in households or with a group of persons with acute respiratory problems and an increase in the number of new COVID-19 infections in the geographic area
  • possibility of disease being spread by persons with unexplained symptoms
  • 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?

Treatment focuses on the primary symptoms such as high temperature and coughing. A total of 10% of patients with COVID-19 are referred to hospital. 

Once in hospital they receive additional oxygen or are put on a ventilator depending on the severity of their symptoms. Some people with COVID-19 require intensive medical treatments where doctors provide life support and treat possible underlying diseases or additional bacterial infections. However it is the body’s immune defenses that must combat the virus itself.

Drug treatment

There are currently two drugs approved for treating COVID-19. Remdesivir is an anti-viral drug that shortens recovery time in patients who require oxygen only.

Dexamethasone is an anti-inflammatory drug that is used in people with the severe or critical form of the disease who need oxygen.

Medical associations have recently started to recommend use of tocilizumab in patients whose condition continues to deteriorate but do not yet need additional oxygen. Like dexamethasone, tocilizumab can reduce mortality.

COVID-19 patients should also be given conventional treatment with anti-coagulants such as heparin, unless there are contraindications present.

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

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