Clouds Shift Again: Stratus Dominates, Cicada Stirs

In summer 2025, the Nimbus (NB.1.8.1) and Stratus (XFG) variants were competing for dominance (see previous post Nimbus and Stratus: Cloudy With a Chance of Covid). By that point, earlier JN.1-descended variants such as LP.8.1 had already been largely displaced. That competition is now largely settled, with Stratus and its descendants firmly in the lead across most regions.

As of early January 2026, Stratus (XFG) and its descendants dominate globally. In the U.S., sequencing and wastewater data show XFG making up 60–70% of cases, and when its sublineages (XFG.14.1, XFG.1, XFG.6) are included, the total reaches ~80% by late December. Nimbus has fallen sharply and now accounts for roughly 5% of sequenced cases.

The new variant to watch is BA.3.2 nicknamed “Cicada”.

Unlike recent variants that evolved incrementally from JN.1, BA.3.2 represents a larger evolutionary jump. It's a descendant of early Omicron BA.3, a lineage that largely disappeared in 2022. Cicada was designated by WHO as Variant Under Monitoring (VUM) since December 5, 2025. It has >50 spike mutations vs. BA.3; antigenically distant from JN.1-derived strains

Immune escape appears higher than in currently dominant variants, but there is no evidence of increased severity so far. Anecdotal reports range widely: some people describe near-asymptomatic infections, while others report more symptoms than with prior infections. This variability may reflect individual immune histories or the growing likelihood of co-infections, rather than a fundamentally more severe virus.  

BA.3.2 is not yet globally dominant, but it is growing rapidly in specific regions. In Germany, it jumped from 9% to 38% of sequenced cases in one week in mid-December, overtaking Stratus. Growth has also been observed in parts of the Netherlands, Australia (especially Western Australia), and South Africa. Global prevalence remains low (~2–5%), but some estimates suggest a growth advantage of ~3.5% per day, meaning it could drive late-winter or spring surges.

Importantly, while BA.3.2 may evade antibodies from recent infections or vaccines more effectively, there is no indication it causes more severe disease. Existing immunity still substantially reduces the risk of hospitalization and death.

BA.3 was the least fit of the original Omicron lineages, with unusually weak ACE2 binding—even lower than the Wuhan reference strain - making its reappearance 2 years after BA.3 ceased to circulate (late 2024) entirely unexpected. First detected in South Africa, BA.3.2 joins a long list of divergent Omicron lineages originating in southern Africa, including BA.1, BA.2, BA.3, BA.4, BA.5, and BA.2.86. Since then, BA.3.2 has been detected across Europe, Australia, and the United States, with its geographic spread and persistence suggesting broader transmission than the last highly divergent southern African lineage, BA.2.87.1.

The U.S. is now in its 12th COVID wave. While this wave has not reached the extreme peaks seen in earlier years, transmission is clearly rising. Hospital admissions and ICU use increased ~12–15% in late December. Wastewater data from Biobot show the Northeast and Midwest already surpassing summer 2025 levels, with concentrations continuing to climb

Due to under-testing, only about 1 in 75 infections is currently being captured.

Many people assuming they have “the flu” are likely dealing with COVID or co-infections, a pattern we’ve seen repeatedly during winter surges. Holiday-related reporting delays mean official case counts lag reality, and more “surprise” infections are likely in the coming weeks.

A quick note on flu:

This winter’s influenza season is also intense, driven mainly by H3N2 (subclade K)—a strain that emerged after vaccine strain selection. While this reduces protection against infection, vaccination still significantly lowers the risk of hospitalization and death, especially for children and older adults.

The overlap of flu and COVID symptoms makes testing - and caution - more important than assumptions.


As always, the situation is evolving. 


REFERENCES

Graeme Dor, Dikeledi Kekana, Ryan Hisner, Darren P. Martin, Bette Korber, Timo Ernst, Avram Levy, David Speers, Stuart Turville, Vitali Sintchenko, Kerri Basile, Geraldine Sullivan, Rebecca Rockett, Jen Kok, Federico Gueli, Richard Lessels, Cheryl Baxter, Nicole Wolter, Anne von Gottberg, Houriiyah Tegally, Tulio de Oliveira Identification and genomic characterisation of BA.3.2: a highly divergent BA.3-related SARS-CoV-2 lineage from southern Africa medRxiv 2025.12.19.25342658; doi: https://doi.org/10.64898/2025.12.19.25342658

Zesuliwe Jule, Cornelius Römer, Taskeen Hossen, Victoria Sviridchik, Kajal Reedoy, Yashica Ganga, Siphokazi Silangwe, Alex Norman, Farina Karim, Dikeledi Kekana, Boitshoko Mahlangu, Anele Mnguni, Ayanda Nzimande, Nadine Stock, Mallory Bernstein, Bernadett I. Gosnell, Mahomed-Yunus S. Moosa, Nicole Wolter, Khadija Khan, Richard A. Neher, Alex Sigal Evolution and Viral Properties of the SARS-CoV-2 BA.3.2 Subvariant medRxiv 2025.10.28.25338622; doi: https://doi.org/10.1101/2025.10.28.25338622

Zhang, Lu et al. Epidemiological and virological update on the emerging SARS-CoV-2 variant BA.3.2 The Lancet Infectious Diseases, Volume 26, Issue 1, e1 - e2

COVID-19 Wastewater Data – Variants | NWSS | CDC

Variants and Genomic Surveillance | COVID-19 | CDC

Surveillance and Data Analytics | COVID-19 | CDC

WastewaterSCAN Dashboard

Mike Hoerger, PhD MSCR MBA (@michael_hoerger) / X

https://pmc19.com/data/images/pmc_December292025_08.png

Pandemic Mitigation Collaborative - COVID-19 Data Dashboard

JWeiland (@JPWeiland) / X

The world's first & most advanced wastewater intelligence platform

Respiratory Illness Index | Walgreens

https://www.apotheken-umschau.de/krankheiten-symptome/infektionskrankheiten/coronavirus/corona-variante-nimbus-breitet-sich-schnell-aus-1334311.html

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