CaliciNet Data

Norovirus U.S. Outbreak Map

What to know

• Below are confirmed norovirus outbreaks submitted to CaliciNet and updated monthly.
• Participating public health laboratories electronically submit genotype information for norovirus and basic epidemiology data from norovirus outbreaks to the CaliciNet database.
• The data on norovirus strains are compared with existing norovirus sequences in the CaliciNet database.

Confirmed norovirus outbreaks submitted by state

September 1, 2025 – August 31, 2026

Confirmed norovirus outbreaks submitted by genogroup

September 1, 2024 – August 31, 2026

Genotype distribution of norovirus outbreaks

September 1, 2025 – August 31, 2026 (n=153)

Data Table: September 1, 2025 – August 31, 2026 (n=153)

The Other Genotypes category includes genotypes from outbreaks that each make up less than 5% of the total number of outbreaks. These genotypes are: GI.1[P1] (2.6%), GI.2[P2] (1.3%), GI.3[P3] (3.9%), GI.3[P13] (2.0%), GI.5[P5] (0.7%), GI.6[P11] (2.0%), GI.7[P7] (1.3%), GII.1[P33] (2.6%), GII.2[P2] (0.7%), GII.3[P12] (2.0%), GII.6[P7] (2.0%), GII.9[P7] (2.6%).

Data Table: September 1, 2024 – August 31, 2025 (n=411)

Dual typing for norovirus

Dual typing for norovirus is being implemented by laboratories participating in CaliciNet.

Dual typing is RT-PCR amplification of a partial region of both the polymerase gene and the capsid gene (region B-C) in a single reaction for genogroup I or genogroup II noroviruses.

On This Page

• Confirmed norovirus outbreaks submitted by state
• Confirmed norovirus outbreaks submitted by genogroup
• Genotype distribution of norovirus outbreaks
• Dual typing for norovirus

Sept. 3, 2026

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National Center for Immunization and Respiratory Diseases; Division of Viral DiseasesAbout This Page

Published: May 15, 2024

Updated: September 3, 2026This page was last updated on this date. Updates may include minor edits, image changes, or other modifications to page content.

Reviewed: September 2, 2026The information on this page was last reviewed by subject matter experts to ensure accuracy.

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