Viral Induced Proteins
As aforementioned, the serology testing of COVID-19 is not targeting the virus itself but the antibodies such as IgM and IgG induced following viral infection. These immunoglobulins were serological testing markers for after the patient has early (3 to 6 days after exposure to the virus, IgM) and late virus infection (after 8 days, IgG) response respectively [11]. The serological testing is crucial to identify active patients, asymptomatic carriers or convalescent persons and provide population surveillance. These data could be used to analyze and estimate the SARS-CoV-2 epidemiology and virology [12] and help to contain the outbreak of the pandemic. The highly reactive human could be the donor of convalescent serum for therapeutic [13]. The WHO interim guidance on COVID-19 testing suggested collecting blood, stool or autopsy materials such as lungs (deceased patients) as serology testing specimens [7]. As it has been reported that several factors could contribute to a high false-negative rate (FNR) when using NAAT, serology testing should also be taken into consideration as alternative testing or correlation testing [14]. There are companies such as Guangzhou Wondfo Biotech, China, Innovita Biological Technology, China; Pharma (Berlin), Germany and RayBiotech Inc. US have released various types of test kits that specifically testing on COVID-19 IgM and IgG.