How long can Norovirus survive outside the body and how is it spread?

Norovirus Environmental Survival and Transmission

Environmental Survival Duration

Norovirus can survive for several days on nonporous surfaces, particularly under conditions of low temperature and humidity, making environmental contamination a critical factor in transmission. 1

Key Survival Characteristics

• Norovirus remains infective even when frozen for years or heated to 60°C (140°F) for 30 minutes, demonstrating exceptional environmental stability 1
• Cooking temperatures at boiling or above (100°C/212°F) are required to inactivate norovirus and most other enteric viral pathogens 1
• The virus exhibits remarkable resistance to standard chlorine concentrations—remaining highly infective despite 30-minute exposure to chlorine concentrations as high as 6.25 mg/L, with levels of 10 mg/L necessary for inactivation 1
• Norovirus does not multiply outside the human host, so practices like leaving foods unrefrigerated do not amplify viral loads, though they may indicate poor hygiene practices 1

Transmission Routes

Norovirus spreads through multiple highly efficient transmission routes, requiring as few as 10-100 viral particles to cause infection. 2

Primary Transmission Mechanisms

• Person-to-person transmission is the most important route, occurring through direct contact with infected individuals 3
• Foodborne transmission occurs frequently, with contaminated food handlers being the most commonly implicated source 1
• Waterborne transmission accounts for approximately 23% of documented outbreaks, with contaminated municipal water, well water, stream water, commercial ice, lake water, and pool water all implicated 1
• Fomite transmission occurs through contact with contaminated surfaces and objects, particularly in bathrooms and high-touch areas like door knobs and hand rails 1, 4
• Aerosolized or splattered particles from vomiting or flushing toilets can transmit infection, with shared toilets between rooms identified as risk factors 1

Critical Transmission Factors

• The extremely low infectious dose (10-100 particles) makes norovirus highly contagious 2
• Hands contaminated directly or from surfaces represent the most important means of viral transmission 1
• Asymptomatic individuals can shed virus, though symptomatic individuals shed higher viral loads and are more infectious 5
• Viral shedding continues for 24-48 hours after symptom resolution, maintaining transmission risk even after clinical recovery 6, 7

Disinfection Requirements

Environmental surfaces potentially contaminated with norovirus should be disinfected using sodium hypochlorite (chlorine bleach) solution at 1,000-5,000 ppm concentration, as this is the most effective and well-documented disinfectant 1, 6, 7

Specific Disinfection Protocols

• Prepare bleach solutions fresh daily (within 24 hours) using 5-25 tablespoons of household bleach (5.25%) per gallon of water 1
• Initial cleaning to remove organic material (fecal matter) must be performed before applying sodium hypochlorite, as 5,000 ppm cannot completely eliminate norovirus dried in 20% fecal stool suspension 1
• Contact time of approximately 4 minutes with 5,000 ppm sodium hypochlorite is needed on fecally soiled surfaces to achieve satisfactory viral reduction 1
• Products containing phenolic compounds, triclosan, and quaternary ammonium compounds are less effective against norovirus and should be avoided 1, 6, 7

Hand Hygiene Requirements

Vigorous handwashing with soap and running water for at least 20 seconds is essential, as alcohol-based hand sanitizers have limited efficacy against norovirus 6, 7

• Alcohol-based sanitizers (≥70% ethanol) may serve only as an adjunct between proper handwashings but should never substitute for soap and water 6, 7
• Special handwashing products are not necessary—consistent, vigorous handwashing with regular soap is sufficient 1

Common Pitfalls to Avoid

• Do not rely on alcohol-based hand sanitizers as primary hand hygiene during norovirus outbreaks—they are ineffective against this non-enveloped virus 6, 7
• Do not assume standard chlorine concentrations used in municipal water systems (0.2-5 mg/L) will inactivate norovirus—much higher concentrations (10 mg/L) are required 1
• Do not use phenolic or quaternary ammonium-based disinfectants—these are ineffective against non-enveloped viruses like norovirus 1, 6
• Do not transfer ill patients to unaffected areas except for medical necessity—environmental contamination facilitates ongoing transmission 1, 6