SARS-CoV-2: seroepidemiological pattern in northeastern Bulgaria

SARS-CoV-2 virus is responsible for the current COVID-19 pandemic, which has resulted in more than 2 million confirmed cases and 139,515 deaths in 213 countries, areas and territories as of 20th April 2020. Although reverse transcription polymerase chain reaction is the diagnostic test, screening studies for SARS-CoV-2 antibodies are essential for our extensive knowledge of the viral spread, formation of collective immunity, prophylaxis and treatment algorithms for the infection. We investigated 586 outpatients, for IgM and IgG antibodies, by their request in Varna and the region of northeastern Bulgaria. All of them were patients of medical diagnostic laboratory STATUS, Varna city. We used serological, immunochromatographic tests (rapid tests) at least seven days after suspected viral infection. Twenty-eight of the serum samples were SARS-CoV-2 Ab positive: 4.8% (95% CI: 3.2-6.9%, n = 28). IgM Ab only were detected in 1.0% (95% CI: 0.4-2.2%, n = 6), IgG Ab only in 1.2% (95% CI: 0.5-2.5%, n = 7) and both IgM/IgG Ab in 2.6% (95% CI: 1.5-4.2%, n = 15), from all of the tested individuals (n = 586). In order to understand how many people have contracted the virus, to strengthen our collective immunity and to be able to assess the risk, in the aftermath, it is essential to investigate (IgM/IgG) antibody titers.