Coronaviruses (CoVs) are enveloped, single positive-strand RNA viruses belonging to the large subfamily Coronavirinae, which can infect mammals and several other animals.The continued spread of coronavirus disease 2019 (COVID-19) has prompted widespread concern around the world, and the World Health Organization (WHO), on 11 March 2020, declared COVID-19 a pandemic. Studies on severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS) showed that virus-specific antibodies were detectable in 80-100% of patients at 2 weeks after symptom onset. Currently, the antibody responses against SARS-CoV-2 remain poorly understood and the clinical utility of serological testing is unclear. Little is known about the kinetics, tissue distribution, cross-reactivity and neutralization antibody response in COVID-19 patients. Asymptomatic cases are common but to date there are scarce epidemiological surveys that provide a clear percentage of asymptomatic cases.
A large number of healthcare workers have been infected with the virus worldwide, presenting with severe symptoms to no symptoms at all, in which case being diagnosed on contact tracing only. The seropositivity rate in previously undiagnosed healthcare workers has been reported in different regions of the world. In a combined study of three hospitals of Turkey, the seropositivity rate of the previously undiagnosed HCWs was 2.7%. A study done in China revealed 17.5 % seropositivity rate.
This study will aim to comprehensively review the current knowledge on the immunological changes observed in various healthcare workers in this part of the world, who remained asymptomatic while working in high exposure areas of COVID-19 infection.
