Implementation of an epidemiological surveillance strategy for COVID-19 focused on groups at high risk of SARS-CoV-2 infection

Abstract

The COVID-19 pandemic has been a challenge to implement strategies to mitigate the transmission of the SARS-CoV-2 virus. Asymptomatic transmission among healthcare workers (HCWs) at the front line of care is particularly concerning due to the potential emergence of outbreaks at healthcare centers. With the final goal of early identification and isolation of asymptomatic infected HCWs, we validated a pooled-sample screening and assessed implementation outcomes and results of an epidemiological surveillance strategy carried out during a 12-month period at public health institutions in Bahía Blanca. To develop and validate a coronavirus detection method, RNA was extracted from nasopharyngeal swabs and iden- tification of the viral E gene was done by an “in-house” RT-qPCR using Taqman probes and the human gene RNAseP as a control. Validation against a commercial kit demonstrated high sensibility and specificity of our test (95%, IC 95%: [85%-100%]). To increase our testing capacity, we validated sample pooling (n= 5) prior to RNA extraction. The results showed a sensibility of 73% (IC 95%: [46%- 99%]) and specificity of 100% against individuals. A tailor-made soft- ware called “VIGI-COVID” was designed to properly manage data. A prospective cohort study was conducted since 15/09/20 to 15/09/21. 860 HCWs were included in the epidemiological surveillance and 1765 swabs were performed. The annual cumulative incidence was 2,30% IC95% [1,26% - 3,39%] (20/860), and 43% of the 860 HCWs were swabbed more than once. Our study demonstrated the utili- ty of comprehensive screening of asymptomatic HCWs during the COVID19 pandemic. Early identification and isolation of infected HCWs prevent the onward transmission of SARS-CoV-2, reducing the risk of healthcare-associated outbreaks.