SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) virus is an enveloped, single stranded RNA virus and member of the family Coronaviridae. Coronaviruses have similar structures composed of similar structural proteins including the spike (S), envelope (E), membrane (M), and nucleocapsid (N) as well as several non-structural proteins.
Members of the Coronaviridae family cause a variety of diseases in different vertebrate species. Several human pathogenic coronaviruses are known to exist; besides SARS-CoV-1, SARS-CoV-2 and MERS-CoV, there are HCoV-HKU1, HCoV-OC43, HCoV-NL63 and HCoV-229E. While SARS-CoV-1, SARSCoV-2 and MERS-CoV can cause severe respiratory and systemic diseases, infections with the latter four usually lead to relatively mild cold-like symptoms.
After infection with SARS-CoV-2, the virus accesses host cells via the protein ACE2 (angiotensin-converting enzyme) and causes the disease COVID-19. The severity of disease ranges from asymptomatic, through mild (fever, cold, cough, tiredness, shortness of breath, and loss of smell), and severe, to most severe forms and death. Aging and several co-morbidities (e. g. obesity, diabetes mellitus, cardiovascular diseases, and chronic pulmonary diseases) are described as risk factors for severe progressive forms of COVID-19.
Seroconversion occurs after the acute infection phase of the disease and at different time points depending on the individual but in most cases around 10 - 14 days when the production of IgG antibodies is usually observed. IgG antibodies rise to their highest titre after three to six weeks. Detecting anti-SARS-CoV-2 IgG antibodies provides information about exposure and immune response to SARS-CoV-2, and may be useful for tracking and tracing COVID-19 and epidemiological uses.