Speaker
Description
Background: In 2022, Thailand lifted lockdown and isolation measures, and SARS-CoV-2 was declared endemic by the Ministry of Public Health. The spread of the Omicron variant raised questions about the relative contributions of community versus household transmission to ongoing infections. We analyzed SARS-CoV-2 transmission within the Thailand VERDI-RECOVER study and conducted whole genome sequencing (WGS) and phylogenetic analysis to identify household transmission.
Method: From July 2022 to May 2024, the Thailand VERDI-RECOVER study investigated SARS-CoV-2 transmission in 92 households in Chiang Mai, Thailand, comprising 92 index cases and 193 household contacts. Nasopharyngeal swabs were tested using real-time Polymerase Chain Reaction (RT-PCR, Tellgen, Shanghai, China), and RT-PCR-positive samples underwent WGS using Oxford Nanopore Technology and the ARTIC version 5.3.2 protocol. Phylogenetic analysis of FASTA sequences was conducted using Nextstrain (https://nextstrain.org/), with transmission connections visualized through MicrobeTrace v0.9.0 (https://microbetrace.cdc.gov/MicrobeTrace/).
Results: Among 193 household contacts, 44 (23%) tested RT-PCR positive for SARS-CoV-2. WGS was successfully performed for 83 index cases and 40 household members across 30 households. All viral sequences belonged to Omicron sub-lineages, with BA.5.2 (27%) being the most prevalent. Early study infections were dominated by BA lineages (including BN and JN sub-lineages), while recombinant XBB sub-lineages emerged in April 2023. Phylogenetic and transmission network analyses revealed that 26 of 30 (87%) household infections were due to intra-household transmission. Of the 36 household transmissions identified, 23 (64%) were caused by BA lineages and 13 (36%) by XBB sub-lineages.
Conclusion: This study demonstrates that household transmission was the predominant source of SARS-CoV-2 infections within households in Chiang Mai, Thailand. The genomic analysis provided critical insights into transmission patterns, underscoring the importance of WGS-based monitoring to inform targeted public health interventions.
| Expedited Notification | Yes, I want to opt-in for Expedited Notification |
|---|
