Connecting clusters of COVID-19: an epidemiological and serological investigation

Abstract

Background Elucidation of the chain of disease transmission and identification of the source of coronavirus disease 2019 (COVID-19) infections are crucial for effective disease containment. We describe an epidemiological investigation that, with use of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) serological assays, established links between three clusters of COVID-19. Methods In Singapore, active case-finding and contact tracing were undertaken for all COVID-19 cases. Diagnosis for acute disease was confirmed with RT-PCR testing. When epidemiological information suggested that people might have been nodes of disease transmission but had recovered from illness, SARS-CoV-2 IgG serology testing was used to establish past infection. Findings Three clusters of COVID-19, comprising 28 locally transmitted cases, were identified in Singapore; these clusters were from two churches (Church A and Church B) and a family gathering. The clusters in Church A and Church B were linked by an individual from Church A (A2), who transmitted SARS-CoV-2 infection to the primary case from Church B (F1) at a family gathering they both attended on Jan 25, 2020. All cases were confirmed by RT-PCR testing because they had active disease, except for A2, who at the time of testing had recovered from their illness and tested negative. This individual was eventually diagnosed with past infection by serological testing. ELISA assays showed an optical density of more than 1•4 for SARS-CoV-2 nucleoprotein and receptor binding domain antigens in titres up to 1/400, and viral neutralisation was noted in titres up to 1/320. Interpretation Development and application of a serological assay has helped to establish connections between COVID-19 clusters in Singapore. Serological testing can have a crucial role in identifying convalescent cases or people with milder disease who might have been missed by other surveillance methods.

Rapid development of COVID-19 rapid diagnostics for low resource settings: accelerating delivery through transparency, responsiveness, and open collaboration

“…Antibody detection will also be key to informing exit strategies for the expected long tail of the pandemic and in supporting surveillance by identifying clusters of infection and convalescent cases or people with milder disease that could seed the infection to generate severe cases. 6 The rollout of RDTs is currently marred by a lack of performance data, reference materials, numbers tested and transparency on how tests are being evaluated. Many RDTs have been rushed to market with limited or no independent evaluations of performance.…”

Epitopes targeted by T cells in convalescent COVID-19 patients

“…This includes both humoral and cellular immunity, mediated by antibodies and T cells respectively. Significant attention has focused on understanding antibody responses against SARS-CoV-2 (Yong et al, 2020;Zohar and Alter, 2020;Wu et al, 2020); though, studies informing the role of T cells in conferring protection have started to emerge.…”

Unravelling the modes of transmission of SARS-CoV-2 during a nursing home outbreak: looking beyond the church super-spread event

“…This was in line with the national guidance at the time, that recommended testing for persons with recent travel history or persons with severe respiratory disease. Religious gatherings have been linked to outbreaks of COVID-19 in South Korea, Singapore and the US [13][14][15] . Here, the high prevalence of respiratory symptoms in the community members who attended the church service does suggest that this was an amplifying event.…”