Top 5 Takeaways

1. Omicron Variant Emergence: The Omicron variant was first reported to the WHO by South Africa on November 24, 2021, and designated a variant of concern due to its potential increased transmissibility and resistance to therapeutics.
2. Initial U.S. Cases: Between December 1-8, 2021, 22 U.S. states reported at least one case of the Omicron variant, with 43 cases investigated, resulting in one hospitalization and no deaths.
3. Surveillance and Detection: The CDC uses a multifaceted genomic surveillance system to monitor SARS-CoV-2 variants, including Omicron, and enhanced surveillance was initiated to accelerate detection.
4. Characteristics of Cases: Among the 43 cases, 79% were in vaccinated individuals, and the most common symptoms were cough, fatigue, and congestion. Only one hospitalization was reported, and no deaths.
5. Public Health Measures: Concurrent prevention strategies such as vaccination, masking, improving ventilation, testing, quarantine, and isolation are recommended to slow the spread of Omicron and protect against severe illness.

Original Article Author and Citation

Corresponding Author

Cria G. Perrine, hgk3@cdc.gov

Suggested Citation

Suggested citation for this article: SARS-CoV-2 B.1.1.529 (Omicron) Variant — United States, December 1–8, 2021. MMWR Morb Mortal Wkly Rep 2021;70:1731-1734. DOI: http://dx.doi.org/10.15585/mmwr.mm7050e1

Summary

The Omicron variant of SARS-CoV-2, first reported to WHO on November 24, 2021, has been designated a variant of concern due to its mutations that may increase transmissibility and resistance to therapeutics. Between December 1-8, 2021, 22 U.S. states reported at least one case of Omicron. Among 43 cases investigated, there was one hospitalization and no deaths. Public health measures such as vaccination, masking, and improved ventilation are recommended to mitigate the spread and impact of Omicron.

Methods

The CDC employs a comprehensive genomic surveillance system to monitor SARS-CoV-2 variants. This includes data from the National SARS-CoV-2 Strain Surveillance, contracts with commercial diagnostic labs, and public repositories like GISAID and NCBI. Enhanced surveillance for Omicron was initiated on November 28, 2021, using rapid screening for S-gene target failures (SGTFs) in PCR assays to flag potential cases for genomic sequencing confirmation.

Discussion

The first U.S. case of Omicron was detected on December 1, 2021. The Omicron variant’s rapid emergence highlights the importance of robust genomic surveillance and international information-sharing. Initial cases in the U.S. appear mild, but the variant’s high transmissibility could still overwhelm health systems. Continuous monitoring and research are needed to understand Omicron’s transmissibility, severity, and vaccine effectiveness.

Conclusion

Concurrent prevention strategies, including vaccination, masking, improving ventilation, testing, quarantine, and isolation, are crucial to slow the transmission of Omicron and protect against severe illness. Vaccination, including booster doses, is especially important for those at higher risk of severe disease. Public health measures and robust surveillance systems are essential to manage the spread of SARS-CoV-2 variants.

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