COVID-19 is the name for the pandemic disease caused by the SARS-CoV-2 virus. The first case is thought to have occurred in mid-November in Wuhan, the capital of Hubei province, in China. The virus causes a sometimes fatal outcome in humans and the Chinese CDC informed the World Health Organization (WHO) on December 31st 2019. By January 30th 2020 the WHO declared the disease an Emergency of International Concern. On March 11th the WHO declared it a pandemic emphasizing that it had spread rapidly across all continents and almost every country in the world.
The SARS-CoV-2 virus is a positive-sense single stranded RNA virus closely related to other Severe Acute Respiratory Syndrome (SARS) coronaviruses. SARS-CoV-2 has four structural proteins, known as the S (spike), E (envelope), M (membrane), and N (nucleocapsid) proteins and the N protein holds the RNA genome, while the S, E, and M proteins together create the viral envelope. The S protein mediates viral entry into host cells by first binding to the host ACE2 receptor through the receptor-binding domain (RBD) in the S1 subunit and then fusing the viral and host membranes through the S2 subunit. The RBD residues 331 to 524 of the S1 protein elicits the production of antibodies in the host.
Primary detection of SARS-CoV-2 infection are through PCR-based assays from throat and nasal swabs. These assays detect the RNA of the virus. Serological assays allow the study of the immune response to SARS-CoV-2 in a qualitative and quantitative manner. IgG and IgM assays are needed to determine the precise rate of infection in an affected area, which is an essential variable to accurately determine the infection fatality rate. Serological assays will allow for the identification of individuals who mounted strong antibody responses and who could serve as donors for the generation of serum antibody-based therapeutics. Assays will also permit health authorities to determine who is immune and who is not. This information may be very useful for deploying healthcare workers in a strategic manner to limit the risk of exposure and inadvertent spread of the virus. It could also allow proportions of the population that has already acquired immunity to go back to ‘normal life’.