Top 5 Takeaways

1. First Detection: The Omicron variant was first detected in Botswana on November 11, 2021, and in South Africa on November 14, 2021.
2. Index Patient: The index patient in Nebraska, who was unvaccinated, had a history of symptomatic SARS-CoV-2 infection and returned from Nigeria on November 23, 2021.
3. Household Cluster: All six household members tested positive for SARS-CoV-2, with genomic sequencing confirming the Omicron variant.
4. Reinfection and Symptoms: Five household members had previous COVID-19 infections, and their recent infections were similar to or milder than their first infections.
5. Incubation Period: The median incubation period for the Omicron variant in this cluster was approximately 3 days, shorter than previously described variants.

Original Article Author and Citation

Corresponding Author

Lauren Jansen, rlx8@cdc.gov

Suggested Citation

Jansen L, Tegomoh B, Lange K, et al. Investigation of a SARS-CoV-2 B.1.1.529 (Omicron) Variant Cluster — Nebraska, November–December 2021. MMWR Morb Mortal Wkly Rep 2021;70:1782–1784. DOI: http://dx.doi.org/10.15585/mmwr.mm705152e3

Summary

The Omicron variant of SARS-CoV-2 was first detected in Botswana and South Africa in November 2021. In Nebraska, a cluster of six probable cases was identified in one household, with the index patient having returned from Nigeria. Genomic sequencing confirmed the Omicron variant in all six cases. The index patient and four household members had previous COVID-19 infections, and their recent infections were similar to or milder than their first. The median incubation period for Omicron in this cluster was approximately 3 days.

Methods

The Nebraska Department of Health and Human Services conducted RT-PCR testing and genomic sequencing on specimens from the six household members. Phylogenetic analysis was performed to determine if this cluster represented an independent introduction of Omicron into the United States. A detailed epidemiologic investigation was also conducted.

Discussion

This investigation suggests a shorter incubation period for the Omicron variant and a clinical syndrome similar to or milder than previous variants in vaccinated or previously infected individuals. The findings highlight the potential for reinfection and the importance of vaccination and other prevention strategies. The study’s conclusions are limited by the small sample size, and more data are needed to fully understand Omicron’s epidemiology.

Conclusion

The emergence of the Omicron variant underscores the importance of vaccination and other preventive measures to protect against COVID-19 and reduce the likelihood of new variants. Robust genomic surveillance is crucial for detecting and responding to emerging variants of concern.

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