CDC Issues Updated Guidance for Norovirus Disinfection

The use of chemical disinfectants is one of the key approaches to interrupt norovirus spread from contaminated environmental surfaces. Particular attention should be given to the likely areas of greatest environmental contamination such as bathrooms and high-touch surfaces (e.g., door knobs and hand rails). Sodium hypochlorite (chlorine bleach) has been widely recommended to disinfect human norovirus from surfaces, and its efficacy has been well documented. Environmental surfaces potentially contaminated with norovirus should be disinfected using a sodium hypochlorite solution or other commercial product registered with EPA as effective against norovirus. A list of EPA-approved products is available at Products containing phenolic compounds (including triclosan and quarternary ammonium compounds) are less effective against nonenveloped viruses such as human norovirus. Furthermore, this list should be interpreted with caution because the efficacy of these products is determined by using the surrogate FCV, which exhibits different physiochemical properties than human norovirus and therefore might not reflect a similar disinfection efficacy profile. In addition, several recent reports have demonstrated that FCV is not the most resistant surrogate virus to predict inactivation of human norovirus. Therefore, the use of multiple surrogate viruses rather than a single surrogate has been suggested to assess the efficacy of disinfectants.

Because of this uncertainty, whenever possible, chlorine bleach solution should be applied to hard, nonporous, environmental surfaces at a concentration of 1,000-5,000 ppm (5-25 tablespoons household bleach [5.25%] per gallon of water). Given the potential for evaporative dilution, bleach solutions should be freshly prepared for use within 24 hours, or the target concentration should be doubled (e.g., 2,000-10,000 ppm) for storage and used within 30 days. Although the upper end of this range has been recommended previously when soiling is present, few data are available to support the effectiveness of sodium hypochlorite on fecally soiled surfaces. For example, 5,000 ppm of sodium hypochlorite was not able to completely eliminate norovirus dried in 20% fecal stool suspension on surfaces. A recent study indicated that longer exposure times (approximately 4 minutes) of 5,000 ppm sodium hypochlorite on fecally soiled surfaces were needed to inactivate both human norovirus surrogates (MNV and FCV) by 4 log, which has been proposed as a satisfactory reduction level for norovirus contamination. In conclusion, initial cleaning of contaminated surfaces to remove organic loads such as fecal material should be performed before sodium hypochlorite disinfection.

In healthcare settings, cleaning products and disinfectants used should be EPA-registered and have label claims for use in healthcare settings; personnel performing environmental services should adhere to the manufacturer’s instructions for dilution, application, and contact time. Heat disinfection (i.e., pasteurization to 140°F [60°C]) has been suggested and used successfully under laboratory conditions, for items that cannot be subjected to chemical disinfectants such as chlorine bleach. Other disinfection approaches such as ozone, hydrogen peroxide, or coating surfaces with antimicrobial materials (e.g., titanium dioxide [TiO] film) also have been proposed for routine environmental control of noroviruses.


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