Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is relentlessly evolving,
with emerging variants exhibiting heightened transmissibility and immune escape capabilities.
Understanding the genetic diversity and seasonal transmission dynamics of SARS-CoV-2 in
Thailand is crucial for implementing effective public health interventions. This study aims to
elucidate the genetic diversity and seasonal transmission patterns of SARS-CoV-2 among
patients with acute respiratory illness in Thailand in 2024. Among 8,096 Acute Respiratory
Infection (ARI) cases analyzed, 1,152 samples tested positive for SARS-CoV-2, resulting in a
positivity rate of 14.2%. The majority of infections occurred during a significant outbreak from
late summer to early rainy season, particularly between April and June, accounting for nearly
49% of all positive cases. The highest infection rate occurred in adults aged 31–40 years, with
no significant association between gender and infection status (p = 0.583). Extensive genomic
sequencing identified over seven distinct SARS-CoV-2 lineages, with the JN.1 lineage dominating
early in the year. Recombinant variants, notably XEC, XDV.1, and XDY, emerged as significant
contributors to the evolving landscape, reaching a prevalence of 57.1% by December.
Phylogenetic analyses demonstrated a consistent evolutionary rate and identified critical
emergence dates for new lineages, underscoring the virus's ongoing evolution in Thailand. Our
findings emphasize the necessity of continuous genomic surveillance for tracking variant
transmission dynamics and managing public health responses effectively. Furthermore, the
evolving genetic landscape of SARS-CoV-2 highlights the urgent need for adaptive vaccination
strategies aligned with seasonal transmission patterns in Thailand.
