Los Angeles and Northern California are experiencing a significant late-spring surge in norovirus activity, according to wastewater surveillance and recent outbreak reporting from state and federal health systems. The increase is unusual for a virus typically associated with winter peaks, raising concerns among public-health officials about shifting seasonal transmission patterns.
Recent CDC-linked outbreak tracking shows more than 1,190 norovirus outbreaks reported between August 2025 and May 2026 across participating states, with continued elevated activity into late spring 2026. Centers for Disease Control and Prevention monitoring systems indicate that viral load in wastewater remains high across parts of California, particularly in densely populated urban regions.
