Targeted Sanger Sequencing of a Cluster of COVID-19 Cases in the Surgical ICU of a Non-COVID Hospital: Lessons Learned.

Small clusters of infection due to SARS-CoV-2 in a non-COVID-19 healthcare facility can disrupt services. Here, we investigated a cluster of SARS-CoV-2 cases by targeted Sanger sequencing and clinical epidemiological methods in a non-COVID-19 super-specialty hospital. Epidemiological data were collected in a blinded manner using a proforma to find the risk factors associated with infection. Targeted Sanger sequencing of the spike protein receptor binding domain (RBD) coding region was performed on all the available real-time reverse transcription polymerase chain reaction (RT-PCR)-positive samples that included a patient, his mother, and 11 healthcare workers (HCWs) to determine any genomic variations in the samples from the cluster. All positive cases were due to the Delta variant. However, it detected a unique mutation, N501I, in the RBD region of the SARS-CoV-2 strains. The viral genome extracted from the mother's sample lacked the mutation, thus excluding her from the cluster and pointing out that the outbreak was nosocomial, leading to a focus on infection control measures. Though whole genome sequencing is more universally accepted, in this study, targeted sanger sequencing provided a rapid and cost-effective solution to correctly delineate between the actual cases that form the cluster and other community cases in a pandemic situation.