The virology of SARS-CoV-2

The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has far-reaching effects on society, the economy and medical treatment. Therefore, it is all the more important to understand the characteristics of the virus and to utilize them in the diagnostics, treatment and epidemiology. This article firstly elucidates the medical significance of coronaviruses in general. Then angiotensin-converting enzyme 2 (ACE2) as the binding site of SARS-CoV-2 and the possible influence on disease susceptibility are explained. The gold standard for detection of an active SARS-CoV-2 infection is the direct detection of the pathogen with nucleic acid amplification techniques. At the onset of symptoms a swab of the upper airway is especially suitable due to the high viral load. At a later stage direct detection can be achieved in samples from the lower airway or in stool and anal swabs. Antibody tests cannot replace the direct detection of the pathogen; however, the detection of immunoglobulin G antibodies is of special interest for epidemiological questions (seroconversion time of sometimes several weeks). The plaque reduction neutralization test exclusively detects antibodies which neutralize viruses but the procedure is complicated and can only be carried out in secure laboratories (L3). In addition, the importance of these antibodies with respect to immunity against a second infection is uncertain. Thanks to modern techniques thousands of SARS-CoV-2 sequences are already available, which show a genomic variability. The D614G mutation in the S spikes seems to cause a higher infectiousness. Mutations can impair the diagnostics and treatment, which makes monitoring necessary.