05/30/2026
Norovirus is circulating at high levels across the United States right now, and wastewater surveillance data shows concentrations climbing sharply in the Northeast and San Francisco Bay Area.
'At the national level, norovirus is still in the HIGH category due to high concentrations over the last 21 days.' — Amanda Bidwell, Scientific Program Manager, WastewaterSCAN
WastewaterSCAN, a joint surveillance program run by Stanford and Emory universities, has tracked norovirus signals from August 1 through May 7 of the current season.
Bidwell explained why wastewater data matters more than clinical reports for this particular virus: 'Monitoring norovirus in wastewater is very helpful for this highly contagious virus, as there is not a lot of clinical data to describe outbreaks because most people recover at home without seeing a healthcare professional.'
A newer norovirus variant is contributing to spread, though not because the virus itself became more aggressive.
'The newer variant isn't more contagious in and of itself. It can spread more easily because fewer people have partial immunity to it, so they will get sick and spread the virus.' — Dr. Scott Roberts, Associate Medical Director of Infection Prevention, Yale School of Medicine
Southern California hiking trails have also seen documented norovirus cases, linked by the Pacific Crest Trail Association to shared water sources and high-contact trail environments.
Dr. Linda Yancey, an infectious disease specialist at Memorial Hermann in Houston, pushed back against alarm over the California cases specifically: 'There really isn't anything unusual about this one in California. They just got unlucky.'
Dr. Aaron Glatt, Chief of Infectious Diseases at Mount Sinai South Nassau on Long Island, emphasized that standard hygiene measures remain the most effective defense — particularly rigorous handwashing with soap and water, since alcohol-based hand sanitizers are less effective against norovirus than against other pathogens.
Infectious disease specialists across the three institutions consistently point to surface disinfection with bleach-based products, thorough cooking of shellfish, and staying home for at least 48 hours after symptoms resolve as the core prevention steps.
This article is for informational purposes only and does not constitute medical advice; consult a healthcare professional if you or someone in your care experiences severe dehydration or prolonged symptoms.
WastewaterSCAN continues real-time tracking, and Northeast-region signals will determine whether the current high-level classification escalates further into late spring.