{Excerpt}
Since its rapid global spread beginning in late 2024, the SARS-CoV-2 variant NB.1.8.1 has progressively displaced older omicron variants, and has established near-total dominance in Asia. More recently, two NB.1.8.1-derived sublineages, PQ.16.1.1 and RK.1, have emerged and expanded substantially, particularly in China and Singapore (...). Specifically, the sublineage PQ.16.1.1 acquired the amino acid substitutions Asp253Gly (within the N-terminal domain), alongside Asn417Thr, Asp420Asn, and Ile478Thr (within the receptor-binding domain) relative to the parental NB.1.8.1 strain (...). Concurrently, the RK.1 sublineage (formally classified as a descendant of the PQ.17.7.2.1 branch) acquired Asp420Asn, His445Pro, and Ile478Thr (...). Furthermore, PQ.16.1.1 has continued to evolve into the SV series sublineages (predominantly SV.2 and SV.2.1), which have maintained all receptor-binding domain mutations, including Asp420Asn, and have subsequently come to dominate the circulating SARS-CoV-2 strains in Singapore (...).
