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Seroprevalence of anti-SARS-COV-2 antibodies in blood donors from Nuevo Leon state, Mexico, during the beginning of the COVID-19 pandemic

Background: The progression and distribution of SARS-CoV-2 is unknown because typically only symptomatic individuals are diagnosed. Aim: We evaluated the seroprevalence of anti-SARS-CoV-2 in blood donors in Nuevo Leon, Mexico as a strategy for asymptomatic case detection of COVID-19 and epidemic progression. Methods/Materials: We tested 1968 blood donors that attended two regional donation centers in Northeast Mexico from January 1st to August 30, 2020, to identify anti-SARS-CoV-2 IgG by chemiluminescent immunoassay. Additionally, routine tests for donors including Brucella, Chagas, HCV, VDRL, HIV-1, and HBsAg identification were performed. Results: We found 77 donors reactive for anti-SARS-CoV-2 IgG (seroprevalence 3.99%) and none of them had reported recent COVID-19 symptoms. Donors aged 18 to 49 years (89.5%) were more likely to be seropositive compared to those aged 50 years or older (10.5%) (P<0.001). Prevalence of antibodies increased each epidemiological (EPI) week, parallel to the report of confirmed cases by RT-PCR, identifying the highest prevalence between EPI week 33 and 35 (10.2% to 19%). The metropolitan area of Monterrey recorded the highest number of cases. Routine tests showed that the prevalence of anti-Brucella was 0.13%, anti-HCV 0.5%, anti-HIV-1-2 0.14%, HBsAg 0.16%, Chagas 0.48% and syphilis 1.06%. Conclusions: There is a growing trend of seroprevalence over time, parallel to the constantly increasing epidemic curve in our region and it was higher under 49 years of age associated with asymptomatic infection in donors from the Nuevo Leon area. Detection of anti-SARS-CoV-2 in blood donors is a potential tool for tracking the progression and identifying population exposure during the SARS-CoV-2 outbreak.