All articles starting with S
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SARS-CoV-2 lineage NT.1
SARS-CoV-2 lineage NT.1 is a Pango-named Omicron BA.2.86 descendant within the JN.1.16 branch, known for descendants NT.2.1 through NT.5 and for carrying the largest 2024 share of spike N481K sequences.
SARS-CoV-2 lineage P.1
SARS-CoV-2 lineage P.1, the Gamma variant of concern, emerged in Manaus, Brazil around November-December 2020 from B.1.1.28, carrying K417T, E484K, N501Y spike mutations, driving Brazil's deadly 2021 second wave before Delta displaced it.
SARS-CoV-2 lineage PD.1
SARS-CoV-2 lineage PD.1 is a Pango-designated Omicron sublineage of LP.8.1 (JN.1 family), designated 30 June 2025, detected at low frequencies in Japan, Brazil, Paraguay, and Canada during 2025.
SARS-CoV-2 lineage PD.2
SARS-CoV-2 lineage PD.2, a Pango-designated Omicron JN.1-descended sublineage (PD.2.1 = B.1.1.529.2.86.1.1.11.1.1.1.3.8.1.4.2.1, S:N532K), first seen December 2024, detected mainly in Brazil in 2025, not a WHO variant under monitoring.
SARS-CoV-2 lineage PP.1
SARS-CoV-2 lineage PP.1 is a Pango sublineage of the variant-under-monitoring LP.8.1 (Omicron BA.2.86 group), recorded in 2025 genomic surveillance in Paraguay alongside LP.8.1.1, LP.8.1.3, NY.6, and PD.1.
SARS-CoV-2 lineage PP.2
SARS-CoV-2 lineage PP.2 is a minor Pango lineage with 16 recorded sequences, first seen 20 October 2024 and last seen 22 March 2025, with sublineage PP.2.1; distinct from the 2020 Brazilian Zeta lineage P.2.
SARS-CoV-2 lineage RG.2
SARS-CoV-2 lineage RG.2, a Pango-named Omicron sublineage (alias RG = B.1.1.529.2.86.1.1.11.1.1.1.3.8.1.2.1.2.2), a deep BA.2.86-descendant branch; sibling RG.3 carries C27649T and G29825T.
SARS-CoV-2 lineage RM.1
SARS-CoV-2 lineage RM.1, a Pango-lineage sublineage of recombinant XFG.5.2.5, designated 9 December 2025 with 3 detected sequences and added to Nextclade reference data in January 2026.
SARS-CoV-2 lineage RM.2
SARS-CoV-2 lineage RM.2, also written RM.2 (alias of XFG.5.2.5.2), is a Pango lineage designated 2025-12-21, defined by spike S:A67V, descending from the WHO-monitored XFG (clade 25C) Omicron JN.1 branch; sibling of RM.1.
SARS-CoV-2 lineage RM.3
SARS-CoV-2 lineage RM.3, a Pango lineage designated 19 March 2026 in pango-designation release v1.39 alongside RS.5; name uses the two-letter RM alias of the Pango nomenclature system and is included in Nextclade reference datasets.
SARS-CoV-2 lineage RT.1
SARS-CoV-2 lineage RT.1, a Pango alias of B.1.1.529.3.2.2.2.2.4.1, is an Omicron BA.3.2-related sublineage defined by spike mutations S:S98F and S:Q173H, associated with the Netherlands and Germany.
SARS-CoV-2 lineage RT.2
SARS-CoV-2 lineage RT.2, a Pango lineage of Omicron BA.3.2 descent from parent RE.2.2.4, defined by spike mutations S:S98F and S:Q173H; designated in 2026 from 13 sampled sequences, distinct from sibling RT.1.
SARS-CoV-2 lineage SC.1
SARS-CoV-2 lineage SC.1, a Pango lineage alias of XFG.6.2.1 defined by mutation C10228T, designated March 2026; a sublineage of the XFG recombinant (LF.7 × LP.8.1.2, Omicron/JN.1 descendant) and parent of recombinant XGW.
SARS-CoV-2 lineage SP.2
SARS-CoV-2 lineage SP.2 is a Pango lineage designated 19 March 2026 alongside SP.1 and SP.2.1, included in Nextclade datasets, and detected in New Zealand genomic surveillance in 2026.
SARS-CoV-2 lineage TB.1
SARS-CoV-2 lineage TB.1, a Pango lineage designated 23 June 2026 within the XFG.5.1.7 branch of the XFG (Stratus) JN.1-derived recombinant; sibling lineages TB.2 and XHA designated the same day.
SARS-CoV-2 lineage TB.2
SARS-CoV-2 lineage TB.2, a Pango lineage designated 23 June 2026, descended from the XFG Omicron branch and parent, with RV.1.1.1, of the recombinant lineage XHA.
SARS-CoV-2 lineage XBB.1
SARS-CoV-2 lineage XBB.1, an Omicron recombinant of BA.2.10.1 and BA.2.75 with spike mutation G252V; noted for extreme antibody escape; parent of XBB.1.5, the 2023 US-dominant variant and 2023-2024 vaccine target.
SARS-CoV-2 lineage XBB.1.16
SARS-CoV-2 lineage XBB.1.16, nicknamed Arcturus, is a recombinant Omicron subvariant descended from XBB (BJ.1 × BM.1.1.1), first documented January 2023, which surged in India, became a WHO variant of interest in April 2023, and differs from XBB.1.5 by spike mutations E180V and T478R.
SARS-CoV-2 lineage XBB.1.5
SARS-CoV-2 lineage XBB.1.5, nicknamed Kraken, is an Omicron recombinant-descendant subvariant carrying spike F486P that dominated global COVID-19 in early 2023 and became the target of 2023-2024 updated vaccines before JN.1 displaced it.
SARS-CoV-2 lineage XBB.1.9
SARS-CoV-2 lineage XBB.1.9, an Omicron XBB sublineage defined by ORF1a G1819S and T4175I; parent of EG.5 (XBB.1.9.2) and HK.3, marked immune evasion, 29-fold titer drop vs wild type.
SARS-CoV-2 lineage XBB.2
SARS-CoV-2 lineage XBB.2, a Pango sublineage of the XBB recombinant (BJ.1 × BM.1.1.1, BA.2-derived Omicron); WHO-classified as Omicron; its descendant XBB.2.3 was a major 2023 subvariant with an estimated 22% weekly growth advantage.
SARS-CoV-2 Omicron variant
Omicron (B.1.1.529) is the SARS-CoV-2 variant of concern designated by WHO on 26 November 2021 after detection in South Africa; heavily mutated, highly immune-evasive, and the ancestor of all lineages dominating COVID-19 since 2022.
SARSA
SARSA is an on-policy temporal-difference control algorithm for Markov decision processes, introduced in 1994, named for its state-action-reward-state-action update, and known for learning safer policies than Q-learning.
Sarsa Dengel
Sarsa Dengel (ሠረጸ ድንግል), throne name Malak Sagad I, was emperor of Ethiopia from 1563 to 1597, a Solomonic-dynasty warrior king who fought the Oromo and Ottoman-backed rebels.
Sarsina
Sarsina (Sassina), Umbrian then Roman town in the Savio valley, Romagna Apennines; submitted to Rome 266 BC, municipium by 90 BC, birthplace of Plautus, with Pian di Bezzo necropolis and mausoleum of Rufus.
Sarswela
Sarswela (also spelled sarsuwela) is a Philippine form of musical theater derived from the Spanish zarzuela, dialogue-heavy like an operetta, and used for political protest under American rule.
Sarta Oil and Gas Field
The Sarta Oil and Gas Field is an oil field about 35 kilometers north of Erbil in Iraqi Kurdistan, produced from November 2020 until its shutdown in 2023.
Sartak
Sartak (Sartaq, Sartach; Mongolian Сартаг) names a 13th-century khan of the Golden Horde, eldest son of Batu Khan, and several places: the Sartak-Bamo resort and watershed in Iraq's Kurdistan Region, villages in Iran and Erbil, and a Khakassia locality.
Sartang
Sartang (Yakut: Сартаҥ) is a 620 km river in Yakutia, Russia; with the Dulgalakh it forms the Yana, rising from Lake Siskyuele in the Verkhoyansk Range. Also a village in Ilam, Iran, and a language of Arunachal Pradesh.
Sarthak Chugh
Sarthak Chugh is an Indian footwear entrepreneur in Delhi who co-founded the women's footwear brand Shoetopia and founded its sister venture HVNLY By Shoetopia in July 2025.