The Centers for Disease Control and Prevention (CDC) estimates that each year in the U.S. NoVs are responsible for approximately 23 million infections resulting in 50,000 hospitalizations. In addition, NoVs are the leading cause of AGE in the U.S., NoV episodes have taken place on cruise ships and in healthcare settings (hospitals and nursing homes), hotels, retirement centers, and schools.
Although NoVs are currently more of a concern to the general public than to employees, the increasing incidence of NoV outbreaks exposes many different employee groups, especially healthcare workers (HCWs). For example, in a Maryland hospital in 2004, 265 HCWs developed AGE during a NoV outbreak. The percentage of HCWs affected was three times higher than the percentage of patients affected. Similarly, in an Oregon longterm care facility in April 2006 a relatively large number of employees (25) became ill with AGE.
According to the CDC, the usual time from exposure to onset of symptoms is 24 to 48 hours but can be as short as 12 hours. This illness is characterized by:
According to the CDC, NoVs are highly contagious, with as few as 10-100 virus particles being sufficient to cause infection. NoVs are transmitted primarily through food or water contaminated with fecal material. NoVs can also spread via droplets of vomit. Transmission can also occur indirectly when the virus is transferred to the mouth via the hands after contact with environmental surfaces that have been contaminated with either feces or vomit. NoVs are quite stable in the environment and can survive freezing.
There are no antiviral drugs for treatment of NoV infections, and no vaccines are currently available. Illness usually lasts 24 to 60 hours. Dehydration is the most common complication and may require intravenous replacement fluids.
Any surface (porous or non-porous) that is likely to have been contaminated by oral or fecal secretions from a NoV-infected person should be disinfected.
Most effective disinfectants
The CDC recommends using either chlorine bleach or U.S. Environmental Protection Agency (EPA)-approved disinfectants to control NoV outbreaks. All disinfectants should be used on clean surfaces (i.e., surfaces that are not visibly soiled) for maximum performance.
Concentrations and mixing instructions Use for food/mouth contact items, toys; 1 tablespoon of bleach in 1 gallon water (1:250 dilution).
Use for most non-porous surfaces: 1/3 cup bleach in 1 gallon water (1:50 dilution).
Use for heavily contaminated non-porous surfaces: 1 and 2/3 cups bleach in 1 gallon water (1:10 dilution).
Leave bleach on surface for 10-20 minutes and then rinse thoroughly with clean water.
Stability of Chlorine Bleach
Heat disinfection [i.e., pasteurization to 140° F (60°C)] has been used successfully under laboratory conditions for items that cannot be subjected to chemical disinfectants such as chlorine bleach.
EPA-registered disinfectants should be used according to manufacturers’ instructions, including the use of proper PPE recommended by the manufacturer when applying the product. For a list of these disinfectants see: www.epa.gov/oppad001/list_g_norovirus. pdf).
Cleaning large spills of vomit or feces
Non-porous surfaces; Hard surfaces
Porous surfaces: Carpets/Upholstered Furniture
Other porous surfaces: Clothing/linens/ textiles
For procedures, see: www.cdc.gov/ncidod/ dhqp/pdf/guidelines/Enviro_guide_03.pdf.
Occupational Health Policies
Medical Equipment Cleaning Precautions
Employees with potential for NoV exposure should receive training on hazards associated with exposure to NoVs and on hazards the procedures in place in their facility to isolate and report cases and reduce exposures.
Centers for Disease Control and Prevention (CDC) Norovirus (last updated June 6, 2006): www.cdc.gov/ncidod/dvrd/revb/gastro/ norovirus.htm
Environmental Protection Agency (EPA): List G: EPA’s Registered Antimicrobial Products Effective Against Norovirus (Norwalk-like virus) January 16, 2007. www.epa.gov/oppad001/list_g_norovirus.pdf
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