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FAQs on SARS-CoV-2

We receive many questions from citizens and the media regarding the current outbreak of novel coronavirus (SARS-CoV-2). Below, you will find Charité’s answers to the most frequently asked questions.

Please note: The novel coronavirus is known as SARS-CoV-2 (Severe Acute Respiratory Syndrome coronavirus 2). The respiratory illness caused by the virus is known as COVID-19 (Coronavirus disease 2019)

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Interesting facts about mutations

What is a mutation?

The term mutation refers to changes in an organism’s genetic code which can happen over time. The genetic material of viruses – and that of all other organisms – consists of four basic building blocks. A mutation might involve a building block situated at a specific location within the organism´s genetic sequence being replaced with a different one or lost altogether. Mutations are natural occurrences which happen when the virus replicates as part of its propagation cycle. The speed at which mutations occur will differ from virus to virus. Coronavirus genomes change at a much slower rate than that of influenza viruses. However, the rate of mutation during virus replication (the copying of genetic information) only has a limited effect on whether a specific mutation occurs and/or persists. The deciding factor in this respect is the size of the virus population which, in the context of the current situation, means the effectiveness of pandemic control measures. 

Viruses that have accumulated one or more mutations distinguishing them from the original virus are called ‘mutants’. The term ‘variant’ is largely used synonymously. The term ‘clade’ refers to a group of viruses which originate from a common ancestor. Consisting of combinations of letters and numbers, the clade designations currently in use are ‘monophyletic’, meaning they only contain versions of one specific variant. 

SARS-CoV-2 variants carry clade designations such as Alpha (B.1.1.7, first detected in the United Kingdom), Beta (B.1.351, first detected in South Africa), or Delta (B.1.617.2, first detected in India). Each of these variants has a characteristic pattern of mutations.

What are the effects of mutations?

Mutations can have either positive or negative effects on viral characteristics, such as enhancing or reducing the virus’s reproductive capacity or its ability to survive. Most mutations, however, do not have any effect on viral characteristics at all. These are known as ‘neutral mutations’. A specific viral lineage can accumulate multiple mutations. The SARS-CoV-2 clade B.1.1.7 (Alpha), which first emerged in the United Kingdom, has accumulated mutations in usually 17 of its approximately 30,000 genetic coding units. Different mutations can have either compensatory or synergistic effects on viral characteristics. Individual mutations must therefore be evaluated within the context of any other existing mutations. 

Many thousands of SARS-CoV-2 mutations have already been reported globally. By monitoring the distribution and frequency of mutations over time, researchers can observe how the virus evolves and use this information to produce a phylogenetic tree. While this is useful in terms of obtaining information on the development of the virus, the presence of mutations alone does not permit inferences regarding viral characteristics.

Where a noticeable increase in the rate of infections is associated with the appearance of a specific variant, this might indicate the presence of a specific mutation which enhances the virus’s ability to replicate. However, comprehensive and time-consuming laboratory analyses are needed in order to identify a specific effect as unequivocally linked to a particular mutation. 

How are mutations and virus variants identified?

Scientists use a technique known as ‘genome sequencing’ to obtain a complete breakdown of the genetic information contained in a virus. The ability to determine the precise order of a genome’s building blocks enables scientists to identify mutations in the viral genetic code and assign variants their correct places within the SARS-CoV-2 phylogenetic tree. Genome sequencing enables the reliable identification and classification of the SARS-CoV-2 variants which are currently the focus of intensive monitoring. Occasionally, scientists will detect other virus variants which have not previously been identified. While sequencing data enable scientists to draw conclusions about the evolution of the virus, they do not provide information on viral characteristics (see ‘What are the effects of mutations?’).

The equipment needed to perform genome sequencing differs from that used for PCR testing. Genome sequencing (and the subsequent analysis of sequencing data) is also significantly more time-consuming than PCR and can take several days. However, there is a faster way to determine whether a viral sample contains one of the variants currently of concern. This involves the use of a series of mutation-specific PCR tests (‘PCR genotyping’, also referred to as SNP genotyping).

Mutation-specific PCR genotyping enables scientists to confirm within hours whether a particular sample contains specific virus mutations. They might start by looking for the spike gene mutation N501Y, which is common to the Alpha, Beta and Gamma variants. By using other mutation-specific genotyping PCR tests, the researchers can then go on to determine which of these three variants is contained in the sample. If, for example, a sample contains both the N501Y and del H69/V70 mutations, it is currently highly likely that the sample contains the Alpha variant. For quality control and research purposes and as part of molecular surveillance, it is nonetheless advisable for at least a selection of samples to also undergo genome sequencing. 

How does Charité test for mutations?

Testing to identify mutations is carried out at various sites across Charité. This is done for a range of purposes.

  • Labor Berlin, a joint subsidiary of Charité and Vivantes, conducts routine SARS-CoV-2 testing on a large scale. It processes samples from both Charité and Vivantes as well as other institutions. All samples from Charité and Vivantes which test positive for SARS-CoV-2 undergo additional PCR-based genotyping to confirm the presence or absence of the variants currently of particular concern (see ‘How are mutations and virus variants identified?’). The additional testing steps are only performed once the original PCR test results have been obtained and reported. The aim of this additional testing is to monitor the frequency of virus variants within a defined test cohort. The information obtained can be used to establish whether certain variants spread more effectively than others. Furthermore, knowledge of the occurrence of a potentially more transmissible virus variant will enable hospitals and public health care authorities to implement additional infection control measures.

    A proportion of positive samples also undergo additional genetic sequencing. This testing forms part of both quality control and molecular surveillance. All genome sequencing data are stored in the Institute of Virology’s database and made available to researchers. The same data are also transmitted to the Robert Koch Institute and made available to the international GISAID database.
  • The Robert Koch Institute has designated Charité’s Institute of Virology as a Consulting Laboratory for Coronaviruses. In addition to acting in a consulting capacity, providing expertise to other diagnostic laboratories in Germany, the laboratory will also – upon request – assist with the diagnosis and evaluation of individual cases and outbreaks.  As part of this role, the consulting laboratory also tests samples sent from other German locations for the purpose of variant testing. These cases will initially undergo a combination of PCR genotyping assays. A selection of samples will then also undergo SARS-CoV-2 genome sequencing. German laboratories are under no obligation to use the consulting laboratory or notify it of results. For this reason, the consulting laboratory is unable to provide information on the pandemic situation in Germany. 

    The consulting laboratory provides other laboratories with sequencing protocols and technical assistance. The spectrum of services offered by the consulting laboratory also includes a range of other tests and assays from the fields of molecular diagnostics (PCR, mutation testing, bioinformatics), serology (antigen and antibody testing, neutralization tests) and virology. These include a particularly important and complex process known as phenotyping, which involves the isolation of replicating viruses in the laboratory and is followed by laboratory analyses to establish relevant characteristics (replication capacity, neutralization, virus entry, and immune interference). 

Interesting facts about PCR testing

What is a PCR test and what is it used for?

PCR testing uses a technique known as Polymerase Chain Reaction, a molecular biology technique used to make huge numbers of copies of genetic material. Invented in 1983, the technique won American biochemist Kary Mullis the 1993 Nobel Prize in Chemistry. As one of the most important technologies available to the field of molecular biology, PCR has become an indispensable tool for many scientists – both in Germany and internationally. The technology has numerous areas of application, including paternity testing, crime scene investigation, genetic testing for hereditary diseases and the detection of pathogens.

PCR has long been established as a routine tool in the diagnosis and monitoring of infectious diseases caused by bacteria (e.g. tuberculosis), parasites (e.g. malaria) and viruses (e.g. hepatitis A to D, AIDS, influenza). The advantages of PCR – high sensitivity, specificity, and speed – often outweigh those of other technologies. PCR can also provide information on the relative quantities of pathogens. PCR plays a particularly important role in relation to pathogens which cannot (easily) be cultured in the laboratory (such as the hepatitis C virus). 

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How does PCR work?

PCR enables scientists to make millions of copies from even the tiniest amount of DNA in the laboratory. PCR could therefore be regarded as a type of high-speed copy machine for DNA. In order to produce multiple copies of a DNA molecule (known as amplification), the double-stranded DNA molecule must first be separated into single strands. For this, the DNA sample must be heated to more than 90 degrees Celsius (194 degrees Fahrenheit). Which specific section of DNA will be copied (for instance, which specific gene) depends on the ‘primer’ used. Primers are short sections of synthetic, single-stranded DNA. They are designed to bind to sequences of DNA either side of the DNA section to be copied. The sample must be cooled to enable both primers to find and bind to the DNA section. The primers then act as the starting point for the DNA copying process: DNA polymerase (an enzyme which in the body is responsible for DNA replication during cell division) binds to the DNA regions in order to copy the section of DNA marked out by the primers. At the end of this process (for which the temperature of the sample must be increased once again), two copies of the original DNA have been made. This copying cycle, including the heating and cooling steps, is then repeated again and again.

A more advanced variant of PCR, known as qPCR (quantitative PCR) or ‘real time PCR’, enables researchers to not just amplify DNA, but quantify the number of DNA copies in the sample. The technique uses probes which emit a fluorescent signal as soon as they bind to the single strand of DNA to be copied. The strength of the fluorescent signal is therefore a measure of the number of DNA copies present, enabling scientists to estimate the number of DNA molecules which were present in the original sample. What this means for the technology’s use in viral diagnostics is as follows: qPCR enables scientists to estimate the number of copies of viral genetic material (‘viral load’) contained in a sample. This is where the ‘Ct value’ (cycle threshold, also known as Cp or Cq) comes into play. It describes the cycle number at which the fluorescent signal exceeds the background fluorescence. A Ct valued of 30, for instance, means that 30 copying cycles were necessary in order to produce a sufficient number of copies of the DNA present in the initial sample for the probes to be able to detect the signal. This means: the higher the Ct value, the lower the quantity of DNA in the sample. In order to be able to determine the precise viral load in a sample, results must be compared with a reference standard.

Some viruses, such as the measles virus and coronaviruses, use RNA instead of DNA as their genetic material. In order to be able to detect RNA viruses using the PCR method, this viral RNA must first be transcribed into DNA, using the enzyme reverse transcriptase. The method used to detect SARS-CoV-2 and other RNA viruses is known as qRT-PCR, which stands for ‘quantitative Reverse Transcription Polymerase Chain Reaction’.

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What is the ‘Drosten test’?

Shortly after first reports of a new viral infection in Wuhan were made public, a team of researchers led by Prof. Dr. Christian Drosten (Director of Charité’s Institute of Virology on Campus Charité Mitte) started to develop a specific PCR test protocol. The first protocol to be published by the WHO as a guideline for other researchers in mid-January, the Drosten protocol was subsequently also published in the journal Eurosurveillance.

When developing a new PCR assay, researchers must first design specific primers (see ‘How does PCR work?’). To do this, researchers do not need actual viral genetic material, they just need to know the sequence of genetic material to be copied. The team from the Institute of Virology initially focused on RNA sequences from various SARS coronaviruses known to affect humans, as well as others known to affect animals. These included SARS-CoV-1, a virus which first emerged in 2002 but is no longer in circulation. Once the genome sequence for the novel virus (SARS-CoV-2) became available, the researchers found that the sections of RNA targeted by the previously designed primers were identical in both SARS-CoV-1 and SARS-CoV-2. The previously used primers would therefore be able to be used with the novel virus, thus enabling the copying and detection of specific RNA sections using PCR. The researchers started by testing this process using synthetic SARS-CoV-2 RNA, later expanding testing to patient samples.

To ensure the highest possible level of sensitivity (the test’s ability to not miss SARS-CoV-2 infections) and specificity (the test’s ability to not mistakenly identify other infections as SARS-CoV-2), the test protocol describes an assay comprising three lines of testing, targeting three separate gene sequences. In collaboration with other European laboratories, the researchers then subjected the protocol to comprehensive testing (‘validation’). Information on the protocol and the validation process can be found in the Eurosurveillance article.

It is important to note that the published test protocol is not a commercial product. Rather, the protocol comprises a series of instructions (not unlike a cooking recipe) on how to test for SARS-CoV-2 using PCR. Following its publication, the protocol was used widely, enabling the diagnostic detection of SARS-CoV-2 all over the world (see ‘Which SARS-CoV-2 PCR test is being used in Germany?’).

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Which SARS-CoV-2 PCR test is being used in Germany?

Germany operates a decentralized testing program. Independent laboratories offer their clients (ranging from hospitals and health authorities to private practices and even the fire rescue service) a range of laboratory services. Each of these laboratories is free to decide which test it uses for a specific parameter. Diagnostic laboratories generally have two options in this regard. They can either decide to use a commercially available test, for which the manufacturer has obtained the relevant diagnostic approvals (‘CE-IVD’-marked tests; IVD = in vitro diagnostics), or they have to conduct their own testing to confirm the validity of a specific diagnostic test. To do so, laboratories can either use their own ‘in-house tests’ or commercially available tests designed exclusively for research purposes, not for use in diagnostic testing (‘Research Use Only’ or RUO products).

Many German diagnostic laboratories used the information provided in the Eurosurveillance article (see ‘What is the ‘Drosten test’?’). They did so in an effort to set up the necessary diagnostic testing protocols and processes in the shortest time possible. Diagnostics companies also developed a range of commercial products for use in SARS-CoV-2 PCR testing, initially using only the Drosten protocol as a guide, but later also including the protocols of other research groups. All regulatory compliance steps involved (including the approval of the product as a CE-IVD-marked test) were, and continue to be, the responsibility of the diagnostic laboratories and diagnostics companies.

In short, German diagnostics laboratories use a range of different PCR tests for the detection and diagnosis of SARS-CoV-2.

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How reliable is a SARS-CoV-2 PCR test?

As with all other diagnostic testing, the reliability of a SARS-CoV-2 PCR test will depend on a range of factors. It is important that every single one of these factors (and others) is taken into account by the laboratory physician when determining the diagnosis. What this means is that a PCR test result alone is not the same as a diagnosis (see ‘How is SARS-CoV-2 diagnosed?’).
A test’s sensitivity expresses the percentage of correctly identified positive samples (i.e. samples from patients who have the disease). If a SARS-CoV-2 PCR test is highly sensitive, it will only miss a very small number of positive cases. This means it has a very low false-negative rate. German diagnostic laboratories use a range of different tests (see ‘Which SARS-CoV-2 PCR test is being used in Germany?’). Data on technical sensitivity is provided by the tests’ manufacturers and included in the (freely available) package inserts. The technical sensitivity of SARS-CoV-2 PCR tests is generally considered to be very high.
A test’s specificity expresses the probability of the test identifying a healthy person as healthy. If a SARS-CoV-2 test is highly specific, this means it does not accidentally produce a positive result for a person who is infected with a different virus (known as a ‘false positive’ result). German diagnostic laboratories use a range of different tests (see ‘Which SARS-CoV-2 PCR test is being used in Germany?’). Data on technical specificity is provided by the tests’ manufacturers and included in the (freely available) package inserts. The technical specificity of SARS-CoV-2 PCR tests is generally considered to be very high. This also applies to all PCR-based testing in Germany – subject to various aspects other than technical parameters (see ‘How is SARS-CoV-2 diagnosed?’). According to the Robert Koch Institute, PCR tests produce a very low number of false positives, provided tests are conducted correctly and results subject to expert evaluation.
Sample quality
Whether or not a PCR result is reliable largely depends on the quality of the sample used. Was the sample collected from the nasopharyngeal (nose and throat) area, or is it an anterior nasal specimen? Was the sample collected at the correct time during the infection, when the virus is present in the nose and throat? If a sample is taken at a later stage during the infection cycle, SARS-CoV-2 may no longer be detectable in the throat, only in the lungs. Was the sample transported and stored correctly? Inadequate transport conditions may result in any viral RNA being destroyed, resulting in the PCR test returning a (false) negative result.

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How is SARS-CoV-2 diagnosed?

It is important to distinguish between a PCR test result and the final medical diagnosis. Making and reporting a diagnosis is usually the responsibility of a physician. As part of the diagnostic process, a physician will take into account the individual’s PCR result alongside other circumstances specific to the case, such as the patient’s medical history, sample collection and transport. A physician will also take into account other parameters, such as the current pandemic situation.

When faced with indeterminate or invalid results, laboratory physicians will usually repeat testing or retest the sample using a different test in order to confirm or reject the original finding. This also applies to false positive results, which are rare but can happen (see ‘How reliable is a SARS-CoV-2 PCR test?’).

A PCR test result should therefore not be regarded as equivalent to a diagnosis. Estimates regarding false positive and false negative results which are based solely on the technical specifications provided for a specific PCR test are therefore not transferable to any and all PCR testing in Germany.

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What answers can and can’t a PCR test provide?

PCR (and qPCR) can be used to detect and quantify a specific organism’s genetic material (see ‘How does PCR work?’). A positive PCR test result following a nasopharyngeal (nose and throat) swab means that the patient was infected by the virus (because SARS-CoV-2 does not form part of the natural human microbiome). The test’s Ct value (see ‘How does PCR work?’) estimates the quantity of viral genetic material (‘viral load’) contained in the sample and, therefore, the amount of the virus present in the patient’s nose and throat.

A PCR test alone cannot determine whether or not the genetic material detected stems from intact virus particles. To determine whether or not this is the case, the sample will need to be cultured in the laboratory. If the virus can be cultured, this means the sample from the patient’s nose and throat did indeed contain infectious SARS-CoV-2 particles. The process involved in culturing SARS-CoV-2 takes several days. Due to the need for extensive safety precautions and rapid sample delivery, it is also a very complex and time-consuming process which can only be carried out in specialized laboratories. Despite these challenges, researchers across the world (including at Charitè's Institute of Virology) have produced extensive study data comparing PCR test results with viral cultures. In conjunction with other studies, these data suggest that PCR-based evidence of viral load within the nasopharyngeal region is associated with a patient’s ability to infect others.

In short, while PCR alone cannot be used to confirm whether or not a patient is infectious, PCR results can be used to estimate a patient’s infectiousness.

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Questions and answers at a glance


Where can the public find information on getting vaccinated against COVID-19?
Answers to the most frequently asked questions are published by the Robert Koch Institute (RKI) and the Paul-Ehrlich-Institut. The Senate Chancellery of the state of Berlin has provided answers to the questions most frequently asked by the citizens of Berlin.

Suspect you have SARS-CoV-2?

What should citizens of Berlin do if they suspect they may have caught the virus?
The Berlin Senate Chancellery has set up a hotline for citizens who are concerned they may have caught the virus. The hotline number is 030 / 90 28 28 28, answers to frequently asked questions can be found here. To improve accessibility and capacity, all of the districts of Berlin have set up their own hotlines and emails. Citizens can also contact the out-of-hours service of the National Association of Statutory Health Insurance Physicians on 116 117. The out-of-hours physicians provide advice on COVID-19 and will even carry out home visits should this be deemed necessary.

Developed by Charité, the CovApp offers the user the opportunity to conduct a risk assessment at home to help them decide whether or not they should visit the Examination Unit and/or get tested for SARS-CoV-2. As part of its CovApp-based services, Charité also offers video consultations. These are aimed at citizens who are concerned they may have caught the virus but do not show any symptoms or only show mild symptoms. Where a  SARS-CoV-2 test is considered useful or necessary, the individual in question may wish to contact one of the testing units provided by various Berlin-based hospitals. Other testing options include those provided by the Association of Statutory Health Insurance Physicians (KV Berlin), which has a network of 30 dedicated COVID-19 practices. These will treat symptomatic individuals with a suspected diagnosis of COVID-19 who, for whatever reason, are unable to be seen by their own family physician.

  • Only patients with severe symptoms should visit an emergency department. The department should be contacted in advance and notified of a possible case of COVID-19.
  • In emergencies (e.g. breathing difficulties), please contact the emergency services on 112.

[Last updated on 12 October 2020]

Which cases should be tested for SARS-CoV-2?
The guidelines provided by the Robert Koch Institute (RKI) are updated on a regular basis to reflect the current situation in Germany. To obtain the current RKI criteria for SARS-CoV-2 testing, please consult the RKI website.

Tests in asymptomatic individuals are of limited value. The reason for this is that the virus has an incubation period of up to 14 days. A negative test result during these 14 days means that SARS-CoV-2 was not detectable at the time the test was taken, but the infection may still develop. A negative test result obtained during the incubation period therefore does not guarantee that the tested person will remain free of symptoms. Testing people without symptoms can still be useful, for example, as part of the National Testing Strategy.

[Last updated on 5 November 2020]

What does SARS-CoV-2 testing at Charité involve?
Individuals who need to be tested for SARS-CoV-2 have to undergo swabbing. This means taking swabs from their upper respiratory tract (nose and throat) and, where possible, also from the lower respiratory tract (e.g. sputum). A range of testing sites, both within Germany and beyond, collect swabs and send them to Charité for testing; these sites include hospitals, public health authorities, fire stations and doctors’ surgeries.

All SARS-CoV-2 testing takes place at the main laboratory of Labor Berlin, a company jointly owned by Charité and Vivantes. When the swabbing samples arrive at the main laboratory’s ‘specimen reception’, all of the relevant specimen-related information is entered into the laboratory information management system. The samples are then sent to Molecular Diagnostics. This unit, which is responsible for testing the specimens, is staffed by more than 30 employees and is subject to the strictest safety standards.

As a first step, the samples have to be pre-processed. For dry swabs, this is a rather lengthy and laborious process, which involves the viral pathogens contained in the sample having to be manually transferred into a special liquid medium. This is followed by the extraction of the genetic material (viral RNA), a process involving the use of chemical techniques to break open the viral shell and release the viral RNA. A number of different steps are then used to break up this genetic material in order to isolate it from the remaining contents of the sample. Once purified in this manner, the viral RNA is transferred to the test equipment where a real-time RT-PCR assay takes place. The assay involves the use of reverse transcriptase (RT) to ‘translate’ viral RNA into DNA. The DNA produced is then copied multiple times (amplified) using a technique known as Polymerase Chain Reaction (PCR). After this, virus-specific DNA probes are used to detect the virus. The entire process is closely monitored by specially trained medical technology staff.

All test results are evaluated by a physician, who produces a report without delay. Evaluation and reporting takes place 24/7. If the test result is inconclusive, the assay is repeated. As soon as a conclusive result is available, this is transmitted electronically to the physician who submitted the original specimen. Staff from the physician’s practice then contact the person from whom the specimen was collected to let them know whether or not they have been infected with SARS-CoV-2.

Rapid antigen tests

What are rapid antigen tests?
Unlike PCR, which identifies viral genetic material, antigen tests detect the presence of viral proteins (see How does PCR work?’). The test is similar to a pregnancy test, except that it uses a respiratory specimen (usually a nasopharyngeal swab). Rapid antigen tests can be conducted at the point of care without any special laboratory equipment. Antigen tests are quick, producing results in less than 30 minutes.

[Last updated on 17 November 2020]

How reliable are rapid antigen tests?
Antigen tests generally perform less well than PCR tests. In some cases, they may miss SARS-CoV-2-positive samples (lower sensitivity) or falsely identify samples as positive which are not infected with SARS-CoV-2 (lower specificity). Antigen test sensitivity is highest shortly after the onset of symptoms. Their reduced sensitivity therefore has comparatively little impact during this crucial, early phase of the infection. Given the primary purpose of these tests is rapid point-of-care testing, the false positive rate of many of the commercially available rapid antigen tests (approximately 1 in 100) is rather low. To ensure that a positive antigen test has correctly identified a person with SARS-CoV-2, the result must be confirmed with a PCR test.

It is important to note that antigen tests can only provide very limited information. They can, for instance, provide an estimate of a person’s infectiousness (especially when used shortly after the onset of symptoms). They cannot, however, determine whether or not a person is infected at the time of testing. Even a negative result, therefore, cannot rule out infection: the person tested might be positive but only producing low levels of infectious virus at the time of testing. 

The use of antigen tests can prove particularly useful in certain situations (see the information provided by the Robert Koch Institute), such as in point-of-care settings where a quick (initial) decision regarding infectiousness is essential – for instance when testing visitors to care homes or hospitals.

A whole range of commercially available antigen tests have been developed during 2020. Charité’s Institute of Virology carried out its own independent testing to produce estimates of reliability for seven of these commercially available tests. To be included in testing, tests had to be either commercially available in Germany at the time of testing (late September to early October 2020) or available as a prototype which could be ordered from either the manufacturers or dealerships within Germany. Reliability estimates were produced for a range of different samples, including nasopharyngeal swabs, infectious virus from cell culture, and synthetic virus protein.
To ensure that both experts and the public have access to results as quickly as possible, the authors published their manuscript to a preprint server in November 2020.  After completion of the pre-publication review process, including a review by independent experts (peer review), the manuscript was published in The Lancet Microbe in April 2021. Please click here to access the article. Please note: These results exclusively refer to samples collected by medical personnel. They are not transferable to samples which have been collected by laypersons (for instance in the case of home testing kits).

[Last updated on 16 April 2021]

What are the key issues to be aware of with regard to rapid antigen testing?
The Robert Koch Institute (RKI) has collated detailed information on self-administered rapid antigen testing. A diagram and interactive tool help the user to understand results obtained using rapid antigen testing, explaining that the quality of the evidence obtained depends on both the quality of the test itself and the proportion of positive cases among the individuals tested.

According to a study by Charité’s Institute of Virology, the performance of rapid antigen tests is significantly reduced if they are stored and/or used outside the temperature range recommended by the manufacturer. The tests produce more false positives when used at cold temperatures and more false negatives when used at warm temperatures. The test's performance starts to suffer when the test has been exposed to too high a temperature for just 10 minutes, or when the test is used after just 30 minutes of exposure to a temperature that was too low. It is therefore recommended that users should read the package leaflet carefully, paying close attention to the temperature at which it should be stored and ensuring the test reaches the required temperature (room temperature) prior to use. Tests should also be protected from rapid temperature changes.

[Last updated on 16 April 2021]

The disease COVID-19

What is known about symptoms and the course of COVID-19?
The Robert Koch Institute is compiling new findings on novel coronavirus and the disease COVID-19 in a fact sheet. Since the amount of data is growing rapidly, the document is updated continuously.

What are the likely health effects of SARS-CoV-2?
It is essential to distinguish between effects on the individual and effects on the health care system.

  • How does the virus affect the individual?
    Based on current knowledge, the severity of the disease varies widely, ranging from asymptomatic infection to severe pneumonia with lung failure and death. While men and women are equally likely to contract SARS-CoV-2, men appear to be at increased risk of developing more severe symptoms. At-risk groups, i.e. those at risk of more severe disease, include older persons (with the overall risk increasing steadily after age 50 to 60), smokers, severely obese persons and people with certain pre-existing medical conditions (such as cardiovascular diseases, diabetes, chronic respiratory/lung/kidney disease, cancer or immunodeficiency). Even younger people and persons without any pre-existing conditions can develop a severe form of the disease.

    SARS-CoV-2 does not only affect the lungs – it is capable of infecting other organ systems too. In Germany, the most commonly recorded symptoms include cough, fever, a blocked or runny nose and a change in one’s sense of smell or taste. Due to COVID-19 being an emerging disease, it is too early to make reliable predictions as to potential long-term effects or long-term damage as a result of either the disease or its treatment (e.g. long-term ventilation).
  • What effects will the virus have on the health care system?
    It is impossible to predict the overall impact of SARS-CoV-2 on the German health care system. This is mainly due to the rate at which the virus is spreading. If the infection spreads very slowly, this will ensure the health care system has sufficient capacity to cope with the additional pressure created by having to treat COVID-19 patients. If, however, the infection spreads very quickly, this will result in a sudden and significant increase in the numbers of people requiring treatment.

    This would mean having to treat large numbers of COVID-19 patients in addition to patients already receiving treatment for other conditions. Maintaining a normal level of service under these conditions would constitute an enormous challenge for the health care system. The aim of the current strategy is therefore to slow the spread of SARS-CoV-2 as much as possible in order to prevent any such shortfalls in capacity. Everyone can and should help to achieve this – including individuals with a low risk of developing severe symptoms (please see 'How to protect oneself against infection').

[Last updated on 24 November 2020]

How to protect oneself against infection

What can I do to help control the pandemic?
The current approach to the pandemic is to slow the spread of infection. Everyone can and should implement actions to support this. It is crucial that, in addition to protecting themselves against infection, people also focus on protecting other people. Key to this are the ‘AHA+A+L rules’. The acronym, which is intended to serve as a mnemonic device, stands for: distance (Abstand); hand hygiene (Hygiene); face masks (Alltag mit Masken); Corona-App (App); and ventilation (Lüften).

The European Centre for Disease Prevention and Control (ECDC) has compiled a list of tips and recommendations on how to protect oneself and others. The Federal Center for Health Education (BZgA) has published a number of infographics summarizing key hygiene tips (for download and printing).

[Last updated on 12 October 2020]

What are the anti-SARS-CoV-2 measures currently in place in Berlin?
The Berlin Senate Chancellery’s website provides a list of the SARS-CoV-2 pandemic control measures currently in place in Berlin.

[Last updated on 12 October 2020]

Charité measures to ensure safety across all clinical settings

What is Charité doing to protect its staff and patients against infection?
At Charité, ensuring the safety of patients and staff is of the highest priority. Since March 2020, medical staff have been obliged to wear surgical masks throughout the duration of their shifts. For aerosol generating procedures on COVID-19 patients, staff must wear FFP2 masks. In April 2021, this mandatory mask rule was extended to patients and visitors across all clinical settings. Please click here for detailed information on the relevant rules and the right way to put on and wear face masks.

Charité also has visitor restrictions in place to reduce the risk of infection; the current regulations can be viewed here. These measures are intended to protect the health and wellbeing of both patients and staff.

[Last updated on 26 April 2021]

How does Charité prevent silent transmission?
Early on in the pandemic, Charité introduced testing for all staff with suspected SARS-CoV-2. In the spring, Charité conducted a cross-sectional study of more than 7,500 members of staff (primarily those in clinical settings) to establish the prevalence of COVID-19 among its staff. This revealed a very low prevalence of less than 0.5 percent and no evidence of increased rates of infection affecting specific areas of the hospital. Antibodies were detected in fewer than 2 percent of those tested. These results are evidence of the successful implementation of robust hygiene measures across all areas of Charité and the significance of securing the correct personal protective equipment for its staff. Charité continues to pursue a policy of regular staff testing. This particularly applies to staff in sensitive clinical areas such oncology and geriatrics, as well as staff working in Charité’s emergency departments.

To complement arrangements already in place for its staff, Charité introduced routine testing for all inpatients in early May. Both of these measures combined (screening tests for both staff and patients) will continue to ensure that the hospital remains a safe area during the COVID-19 pandemic.

[Last updated on 12 October 2020]

Is it still safe to visit the hospital in case of an emergency?
In the case of symptoms which are indicative of serious, acute medical conditions such as heart attack or stroke, you should continue to use 112 to call for help. Individuals with these types of conditions must be taken to hospital and treated immediately. Delays in medical treatment can have serious consequences. Patients with COVID-19 are treated on entirely separate wards. For a short summary of the typical symptoms of heart attack and stroke, please click here.

Yes. In order to create additional bed and staffing capacity for COVID-19 patients, and to reduce the risk of infection, hospitals have postponed many elective procedures and put in place wide-ranging visitor restrictions. Urgent procedures (e.g. Cancer treatments), however, continue as normal. This of course includes acute and emergency care.

[Last updated on 12 October 2020]

What is Charité doing to ensure that all patients will continue to receive the care they need?
Even during these challenging times, Charité’s aim remains the same: ensure that every patient – regardless of their condition – will continue to receive the best possible care and treatment.  Depending on the course and severity of the pandemic, it may become necessary to reduce (to varying degrees) the provision of certain clinical services in order to ensure sufficient capacity to treat COVID-19 patients.

[Last updated on 12 October 2020]

Blood donations

Is it OK to continue donating blood?
Healthy individuals can continue to donate blood. There is an urgent need for both blood and plasma donations. Donations have decreased dramatically over the past few weeks. However, blood donations are very important. In addition to being used for patients who need blood transfusions, they are also used to make medicines. Blood donations are permitted and welcome, even during the current crisis and even during current restrictions on public life.

There is currently no evidence to suggest that SARS-CoV-2 is transmitted via blood or that a patient could get infected through blood from an undiagnosed case. Irrespective of the current situation, all blood donations are subject to a range of safety measures. Individuals showing signs and symptoms of infection are not permitted to donate blood. All donors are evaluated by medically trained staff. All donors will have their temperature taken and must answer a standard set of questions. As a precautionary measure, individuals who have returned from risk areas, as well as those who have been exposed to a confirmed case of COVID-19, will be precluded from donating blood for a minimum period of two weeks.

The donor centers will also wish to ensure that donors are not placed at an increased risk of contracting SARS-CoV-2. Visitors to these centers must therefore make sure to keep a minimum distance of 1.5 meters between themselves and others at all times as well as wear face masks.

At Charité, blood donations are currently being accepted on both Campus Charité Mitte (CCM) and Campus Benjamin Franklin (CBF).

Blood donations on CCM (Transfusion Medicine and Cell Therapy Center)
Schumannstraße 22, 10117 Berlin
Tel: 030 / 450 525 167, email: blutspende(at)

Blood donations on CBF (Institute of Transfusion Medicine)
Schumannstraße 22, 12203 Berlin
Tel:  030 / 80681-0, Contact

Potential donors are advised to contact the relevant donor center for information on conditions to be met before arrival. Please note: The donor centers will not be conducting tests for SARS-CoV-2.

For further information on blood donations during the current SARS-CoV-2 pandemic, please consult the following websites: DRK Blood Donation Service [DRK-Blutspendedienst Nord-Ost], Robert Koch Institute and Federal Center for Health Education [Bundeszentrale für gesundheitliche Aufklärung].

[Last updated on 12 October 2020]

Further information

For comprehensive and up-to-date information on SARS-CoV-2 (including information for health care professionals), please consult the information provided by the Robert Koch Institute or the European Centre for Disease Prevention and Control.

Citizens of Berlin will find additional information on the website of the Berlin Senate Department for Health, Care and Equality.

En una columna de la Deutsche Welle, el virólogo de Charité, Prof. Dr. Felix Drexler, responde a las preguntas sobre la pandemia en español.