Since late December 2019, an outbreak of a novel coronavirus disease (initially known as 2019-nCoV and subsequently named COVID-19)1 was first reported in Wuhan, China2, which has subsequently spread becoming a global pandemic – as declared by the World Health Organisation (WHO) on 11th March, 2020. COVID-19 has caused significant impact on healthcare systems and caused societal disruption as the potential public health threat posed by COVID-19 is high3. In general, COVID-19 is an acute resolved disease, but it can also be deadly, with a 2% case fatality rate.
SARS-CoV-2 is a single-stranded RNA coronavirus4. The viral infection causes a series of respiratory illnesses including severe respiratory syndrome, indicating the virus most likely infects respiratory epithelial cells and spreads mainly via the respiratory tract from human to human4. Coronaviruses are composed of several proteins including the spike (S), envelope (E), membrane (M), and nucleocapsid (N)5. The spike glycoprotein of SARS-CoV-2 is a trimeric protein with each 180 kDa monomer consisting of 2 subunits (S1 and S2) which facilitate attachment and binding to the target cell6.
Viral infections are characterised by elevations in specific IgM antibody levels 3 to 5 days after the onset of symptoms; the presence of these antibodies generally persists for 30 to 60 days. IgG levels also become elevated after 10 to 14 days and remain detectable for many years.