Health Advisory Regarding Norovirus Activity in MT


Montana is currently experiencing increased levels of community-wide norovirus activity impacting residents and staff of long-term care facilities and assisted living centers. Since the beginning of this year, nearly 500 people associated with 20 outbreaks in 13 jurisdictions have been reported ill due to acute gastroenteritis. Montana typically incurs an average of 2 norovirus or Norwalk-like agent associated outbreaks per month, with increased seasonal activity during the winter months.

Local Health Jurisdictions

DPHHS encourages local health jurisdictions to increase awareness in schools, long term care facilities, and assisted living centers. Please visit the DPHHS website for additional information and resources on norovirus. You are encouraged to share this information among your staff, and to forward it proactively to long term care facilities, providers and restaurants in your jurisdiction for their benefit.

Health Care Providers

Providers are encouraged to consider a Norwalk-like virus in patients presenting with an acute gastrointestinal illness and to test accordingly. Health care providers should report all outbreaks of acute gastroenteritis, including suspected outbreaks of norovirus, to their local health department.

Long Term Care Facilities/Assisted Living Centers

Please visit our website for information on norovirus outbreak management in healthcare settings and additional resources. We encourage monitoring for patients presenting with acute gastrointestinal symptoms and reporting cases to your local health jurisdictions to help us detect and contain outbreaks when they occur.

Staff or volunteers suffering from acute gastrointestinal illness should not care for infants, children or other adults; Recommend staff members caring for infants, children or other adults stay home until at least 72 hours after gastrointestinal symptoms have resolved.

Food Handlers/Restaurants

Professionals employed in the food industry can prevent the spread of diseases by following a few simple steps: Ensure food handlers wash hands frequently with soap and running water for at least 20 seconds and always before preparing or handling food; ensure staff use gloves when handling ready-to-eat foods and eating utensils; ensure staff do not prepare food for others while ill with an acute gastrointestinal illness and for at least 72 hours after symptoms end; food service employees are prohibited from working while suffering from an acute gastrointestinal illness (Administrative Rules of Montana 37.110.210) and should be encouraged to remain home until at least 72 hours after symptoms have resolved.

The DPHHS website features valuable information for food handlers. Please visit

DPHHS Technical Guidance on Norovirus: Outbreak Management and Disease Prevention Guidelines for General Settings

The document serves as guidance for hygiene and disinfection procedures for general settings (e.g., workplaces, churches, community gatherings, etc.) during confirmed and suspected norovirus outbreaks.

Norovirus is the most frequent cause of acute gastrointestinal illness in the United States. Norovirus is very contagious and is spread by contaminated food or water, and after touching contaminated surfaces.

General Staff and Visitors

Hand Hygiene: encourage frequent handwashing with soap and running water for at least 20 seconds; Handwashing is especially important after using the toilet or changing diapers, and before eating; Recommend use of ethanol-based hand sanitizers (60-95%) between proper handwashings and when handwashing is not possible.

NOTE: the use of hand sanitizer should be considered an adjunct for and not a replacement of proper handwashing with soap and running water.


Recommend any staff member or visitor with acute gastrointestinal illness stay home until at least 48 hours after symptoms have resolved.

Custodial Staff

Environmental Disinfection: sodium hypochlorite (chlorine bleach) products with activity against norovirus should be used to disinfect surfaces (note: other U.S. EPA-approved cleaning products can be found at:; particular attention should be given to areas most likely to have the greatest norovirus contamination such as bathrooms and high-touch surfaces (e.g., door knobs, computer keyboards and mice, light switches, hand rails, etc.); initial cleaning of contaminated surfaces to remove fecal material or vomitus should be performed before chlorine bleach disinfection; areas visibly soiled with fecal material or vomitus should be cleaned using hot water and detergent, or steam cleaned (note: do not vacuum as norovirus can become airborne); bleach solutions should be prepared for use within 24 hours; do not mix bleach and ammonia solutions, doing so can cause deadly vapors; do not enter food service area with items soiled with fecal material or vomitus; use a utility sink for washing items soiled with fecal material or vomitus.

Recommended Cleaning Agents for Use During Norovirus Outbreak

Porous surfaces such as wood floors or surfaces visibly soiled with vomit/feces: Chlorine bleach, 1 ½ cup bleach in 1 gallon of water, 5,000 ppm (1:10 dilution).

Non-porous surfaces such as handrails, tile floors, counter-tops, sinks, toilets, doorknobs and other commonly handled items: Chlorine bleach, 1/3 cup bleach in 1 gallon of water, 1,000 ppm (1:50 dilution).

Food/mouth contact items, stainless steel and toys mouthed by children: Chlorine bleach, then rinsed with water or dishwasher at 170°F, 1 tablespoon bleach in 1 gallon of water, 200 ppm (1:250 dilution).

Carpet and upholstered fabrics visibly soiled with vomit or fecal spillage. DO NOT dry vacuum as viruses can become airborne: hot water and detergent or steam clean.

Bleach solution must be prepared fresh daily and have 10-20 minute surface contact time. Use unopened bleach for outbreak-related sanitization (open bottles lose effectiveness after 30 days from opening). EPA-registered disinfectants may also be used although effectiveness in outbreaks has not been evaluated.

Warning: cleaning staff should wear protective equipment when handling chemicals.


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