Investigation of a SARS-CoV-2 B.1.1.529 (Omicron) Variant Cluster - Nebraska, November-December 2021

Area of Science:

• Virology
• Epidemiology
• Genomic Sequencing

Background:

• The SARS-CoV-2 B.1.1.529 (Omicron) variant emerged globally in late 2021.
• Initial Omicron cases in the US were reported in early December 2021.

Purpose of the Study:

• To investigate a suspected Omicron variant (B.1.1.529) COVID-19 cluster in Nebraska.
• To determine if the cluster represented an independent introduction of Omicron into the United States.

Main Methods:

• Reverse transcription-polymerase chain reaction (RT-PCR) testing for SARS-CoV-2.
• Genomic sequencing to identify the specific variant.
• Phylogenetic analysis and epidemiologic investigation.

Main Results:

• Six probable COVID-19 cases were identified in a Nebraska household.
• All six cases tested positive for SARS-CoV-2.
• Genomic sequencing confirmed an identical Omicron genotype in all household specimens.

Conclusions:

• The Nebraska household cluster demonstrated an independent introduction of the Omicron variant into the US.
• Travel history was a key factor in suspecting Omicron infection.