Background SARS-CoV-2 emerged in China and spread throughout the world due to its rapid transmission. The exposure rate in the healthy population is unknown, mainly in resource-limited countries. Herein, we estimated the seroprevalence of anti-SARS-CoV-2 antibodies and risk factors among blood donors in Luanda, the capital city of Angola. Methods This was a retrospective study conducted with 343 blood donors. Chi-square and logistic regression were calculated to predict the independent variable for SARS-CoV-2 infection and deemed significant when p < 0.05. Results Seroprevalence of anti-SARS-CoV-2 was 4.7%. Positivity rates varied to age groups (3.5–14.3%), gender (0–5%), area of residence (3.1–.6%), educational level (5.1–10.2%), occupation (4.4–7.7%), and the blood donor category (2.0–5.1%). Past and recent infections were detected in 3.2% and 1.5%, respectively. Blood donors under the age of 20 years (OR: 4.58, p = 0.241) and from non-urbanized areas (OR: 1.86, p = 0.293) presented a high risk related to infection. The infection was higher in blood group A and lower in blood group O. The risk of SARS-CoV-2 infection has increased from January 2020 (OR: 0.03, p = 0.001) to August 2020 (OR: 0.57, p = 0.426). Conclusions We provide an estimate of the exposure of healthy blood donors in Luanda. Also, we detected anti-SARS-CoV-2 in January 2020, indicating that the SARS-CoV-2 could have been imported during the first month of 2020. Further studies should be performed to assess the exposure rate in different groups from Angola.

Co-epidemics happening simultaneously can generate a burden on healthcare systems. The co-occurrence of SARS-CoV-2 with vector-borne diseases (VBD), such as malaria and dengue in resource-limited settings represents an additional challenge to the healthcare systems. Herein, we assessed the coinfection rate between SARS-CoV-2 and VBD to highlight the need to carry out an accurate diagnosis and promote timely measures for these infections in Luanda, the capital city of Angola. This was a cross-sectional study conducted with 105 subjects tested for the SARS-CoV-2 and VBD with a rapid detection test in April 2021. The participants tested positive for SARS-CoV-2 (3.80%), malaria (13.3%), and dengue (27.6%). Low odds related to testing positivity to SARS-CoV-2 or VBD were observed in participants above or equal to 40 years (odds ratio [OR]: 0.60, p = 0.536), while higher odds were observed in male (OR: 1.44, p = 0.392) and urbanized areas (OR: 3.78, p = 0.223). The overall co-infection rate between SARS-CoV-2 and VBD was 11.4%. Our findings showed a coinfection between SARS-CoV-2 with malaria and dengue, which could indicate the need to integrate the screening for VBD in the SARS-CoV-2 testing algorithm and the adjustment of treatment protocols. Further studies are warranted to better elucidate the relationship between COVID-19 and VBD in Angola.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in China and spread to the world. 1 Pneumonia caused by SARS-CoV-2 was named coronavirus disease 2019 (COVID-19) and is currently a public health concern. 2,3 From December 2019 to December 2020, more than 60.1 million cases of infection and 1.4 million deaths, have been reported worldwide. 4 Until December 2020, the Ministry of Health of Angola reported more than 15 000 cases and 345 deaths. 4 The timely diagnosis of SARS-CoV-2 infection is fundamental to ensure controlling of the COVID-19 pandemic, the provision of treatment, and to avoid the worsening of the disease. [5][6][7] In practice, RT-PCR is the only way to confirm the SARS-CoV-2. 8 There are individuals that despite being epidemiologically related and presenting pulmonary radiological findings compatible with SARS-CoV-2, remain RT-PCR negative. 9 Factors such as the sample collecting and processing procedure may affect the result of the PCR assay. 10 Also, RT-PCR does not distinguish virus with active replication from residual RNA, which could cause false results, especially in asymptomatic individuals. 10 Therefore, serologic tests offer an alternative to assess the degree of exposure amongst different population groups. 11 There are no published studies that assessed the rate of exposure and immune response to SARS-CoV-2 in Luanda, the capital city of Angola. Herein, we used serological assay to screen IgM and IgG antibodies against SARS-CoV-2 in individuals from Luanda, to support the Ministry of Health of Angola in the management of the COVID-19.

Background The global emergence of coronavirus disease 2019 (COVID-19) has challenged healthcare and rapidly spread over the globe. Early detection of new infections is crucial in the control of emerging diseases. Evidence of early recorded COVID-19 cases outside China has been documented in various countries. In this study, we aimed to identify the time of SARS-CoV-2 infection circulation by retrospectively analyzing sera of measles patients, weeks before the reported first COVID-19 cases in Angola. Materials and Methods We examined the humoral response against SARS-CoV-2 by using an enzyme-linked immunosorbent assay (ELISA)-based assay on a combined two-step sandwich enzyme immunoassay method. In total, we received 568 study patients with blood specimens collected from 23 September 2019 to 28 February 2020, 442 sera samples that met the criteria of the study were withdrawn and selected from the overall 568 received samples. In this study, we considered seropositives, patients who tested positive for SARS-CoV-2 immunoglobulin G (IgG) and M (IgM) antibodies with the index value >1. Results Of the 442 sera samples that met the criteria of the study, 204 were measles seropositive. Forty out of 204 were confirmed reactive to SARS-CoV-2 viral proteins using IgG and IgM more than 2 weeks before the first reported case in Angola. The humoral response analysis showed significant differences ( p = 0.01) between the IgG and IgM indexes in the unvaccinated measles patients. Similarly, a significant difference ( p = 0.001) was seen between the IgG and IgM indexes in the vaccinated measles patients. Conclusion Here, using the humoral response analysis, we report the identification of early circulation SARS-CoV-2 infection weeks before the first recognized cases in the Republic of Angola.

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