Coronaviridae

The Coronaviridae are a virus family within the order Nidovirales. Their representatives cause very different diseases in different vertebrates such as mammals, birds and fish. The viruses infect the ciliated epithelia of the respiratory tract, where they paralyse the ciliary movements and consecutively cause diseases of the bronchi and alveoli of varying severity.

Coronaviruses are genetically highly variable, and individual virus species can infect several host species by overcoming the species barrier. Such species crossovers have led to infections in humans with, among other things, the SARS-associated coronavirus (SARS-CoV) - the pathogen that caused the 2002/2003 SARS pandemic - and with the Middle East respiratory syndrome coronavirus (MERS-CoV), which appeared in 2012. The coronavirus epidemic 2019/2020, which originated in the Chinese city of Wuhan, is also attributed to a previously unknown coronavirus, which was given the name SARS-CoV-2.

In humans, various coronavirus species are important as pathogens of mild respiratory infections (colds) up to severe acute respiratory syndrome. A total of 7 human pathogenic coronaviruses are known to date:

Alphacoronaviruses

• HCoV-229-E
• SARS-CoV-NL 63

Beta-coronaviruses

• SARS-CoV-2
• MERS-CoV
• HCoV-HKU-1
• HCoV-NL63
• HCoV-OC43
• HCoV-229E
• Novel Coronavirus (COVID-19)

However, it seems certain that other types circulate in the human population. The pathogens take their name from the club-shaped glycoproteins (spike) anchored in the lipid envelope, the arrangement of which gives the virus a characteristic electron microscopic image (corona=circle).

Human coronaviruses are usually the cause of common infections of the respiratory tract. They mainly occur in adults during the winter months and are responsible for 10-15% of common colds. They are transmitted by droplet infection. After an incubation period of about 3 days, rhinitis develops with headache and coughing, fever may occur, but is not obligatory. Rarely, a pneumonia or pleuritides develop.

Among the betacoronaviruses there are pathogens that are the trigger of severe acute respiratory diseases. These are characterized by a high mortality rate. These include:

• Severe acute respiratory syndrome (SARS) - natural reservoir are flying foxes
• Middle East respiratory syndrome (MERS) - natural reservoir are dromedaries
• COVID-19: New Severe Acute Respiratory Syndrome SARS-CoV-2, the disease caused by this new virus is called COVID-19.

RT-PCR is available for the detection of SARS-CoV and MERS-CoV. In addition, numerous antigen tests are available. The SARS-CoV-2 Rapid Antigen Test of detects proteins that are structural or functional components of a pathogen. However, PCR provides more accurate results and a lower rate of false-positive and false-negative test results.

It is believed that the precursor of SARS-CoV-19 originated from wild animals. Currently, the first patients are believed to have contracted the disease in early December 2019 at the Huanan seafood market in Wuhan (population 11 million), which closed on Jan. 1, 2020. Alternatively, a laboratory variant is being discussed.

Individuals who have been in a risk area designated by the Robert Koch Institute, regardless of symptoms, should avoid unnecessary contact and stay home if possible. In the event of acute respiratory symptoms, they should observe cough and sneeze etiquette and subtle hand hygiene and, after calling ahead with information about possible infected contacts, visit an officially designated contact point for highly dangerous infectious diseases.

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2. Hoehl S et al (2020) Evidence of SARS-CoV-2 infection in Returning Travelers from Wuhan, China. N Engl J Med doi: 10.1056/NEJMc2001899.
3. Jiang X et al (2020) Does SARS-CoV-2 have a longer incubation period than SARS and MERS? J Med Virol:10.1002/jmv.25708.