The aim of this observational study was to develop, with the intended users, an epidemic surveillance and response system that will be effective, sensitive, coordinated and appropriate.

The STREESCO project aims to

• Implement active epidemiological surveillance of suspected cases in Benin at strategic sites in accordance with the World Health Organization (WHO) protocol, in support of the national strategy for responding to the CoVID-19 virus.
• To strengthen this national strategy by developing a clinico-epidemiological surveillance system in remote areas of Benin (health centre approach) and Burkina Faso (population survey approach).
• To gain a better understanding of the dynamics of the epidemic and its parameters in Africa thanks to a modern biostatistical and geo-epidemiological analysis of the data collected as part of this project.

Within the framework of the health systems set up by the Benin health authorities, the project aims to develop, with the intended users, an epidemic surveillance and response system that will be effective, sensitive, coordinated and adapted to a context where resources are limited. Following the start of data collection on 01 March 2021, new reforms to the response strategy against CoVID-19 in Benin have led the investigators to opt for a new strategy in order to meet the objectives of the study. The epidemiological surveillance system will be adapted to the reforms, and data collected and processed prospectively on the dynamics of the epidemic will be collected in CoVID-19 screening centres and in public and private health centres. This is the scientific data needed to issue an early warning signal and enable the healthcare system to respond appropriately. The information system will be based on (i) epidemiological surveys in the field, (ii) virological, serological and antigenic tests, (iii) indicators that will enable action to be monitored, adaptation to the epidemic to be assessed and the response capacity of health structures to be controlled. Analysis (biostatistics, geo-epidemiology) of the data collected will provide useful knowledge for a better understanding of the dynamics of the epidemic. Finally, the project will encourage collaboration between African and European researchers and strengthen the capacity of African institutions to set up an epidemic surveillance system.

Inclusion Criteria:

• All volunteering for COVID-19 screening in health units dedicated to COVID-19 activities.
• Having benefited from a COVID-19 test.
• Give free and informed consent to participate in the study.

Exclusion Criteria:

• Subjects who did not give free and informed consent to participate in the study.

This surveillance was carried out in 03 strategic sites: in Cotonou, the economic capital, in Allada, a town on the border of the cordon sanitaire set up in March 2020, and in Natitingou, a town in northern Benin outside the cordon sanitaire. It was based in the health units involved in the response to COVID-19 at the 03 strategic sites. Initially, we included volunteers for COVID-19 screening, contact cases of positive subjects, and health workers present in the centres. Secondly, The study population consisted of pregnant women in the third trimester (≥ 28 weeks) of pregnancy seen for antenatal care (ANC) in the study maternity units of the 03 strategic sites were surveyed in order to describe their serological status with respect to SARS-CoV-2 infection.