cdc stresses hand washing to prevent norovirus infections
the cdc, in updated guidelines, underscored that hand hygiene is the key to prevent norovirus infections, noting that use of soap and water is a more proven strategy than the use of alcohol-based hand sanitizers. infected patients can be isolated under the care of a nursing staff, but asymptomatic people should not be taken to infection-free units until two days after exposure to the virus, the agency recommended.
noroviruses are the most common cause of epidemic gastroenteritis, responsible for at least 50% of all gastroenteritis outbreaks worldwide, and a major cause of foodborne illness. in the united states, approximately 21 million illnesses attributable to norovirus are estimated to occur annually. since 2001, when the most recent norovirus recommendations were published (cdc. "norwalk-like viruses." public health consequences and outbreak management. mmwr 2001;50[no. rr-9]), substantial advances have been made in norovirus epidemiology, immunology, diagnostic methods, and infection control. as molecular diagnostic techniques have improved in performance and become more widely available, detection and reporting of norovirus outbreaks have increased. although the inability to culture human noroviruses in vitro has hampered progress, assessment of the performance of disinfectants has been facilitated by the discovery of new, cultivable surrogates for human noroviruses. in addition, the periodic emergence of epidemic strains (from genogroup ii type 4, gii.4) and outbreaks in specific populations (e.g., the elderly in nursing homes) have been characterized. this report reviews these recent advances and provides guidelines for outbreak management and disease prevention. these recommendations are intended for use by public health professionals investigating outbreaks of acute gastroenteritis, including state and local health authorities, as well as academic and research institutions.
noroviruses cause acute gastroenteritis in persons of all ages. the illness typically begins after an incubation period of 12--48 hours and is characterized by acute onset, nonbloody diarrhea, vomiting, nausea, and abdominal cramps. some persons might experience only vomiting or diarrhea. low-grade fever and body aches also might be associated with infection, and thus the term "stomach flu" often is used to describe the illness, although there is no biologic association with influenza. although symptoms might be severe, they typically resolve without treatment after 1--3 days in otherwise healthy persons. however, more prolonged courses of illness lasting 4--6 days can occur, particularly among young children, elderly persons, and hospitalized patients (17,18
). approximately 10% of persons with norovirus gastroenteritis seek medical attention, which might include hospitalization and treatment for dehydration with oral or intravenous fluid therapy (7,19,20
). norovirus-associated deaths have been reported among elderly persons and in the context of outbreaks in long-term--care facilities (21,22
). necrotizing enterocolitis in neonates, chronic diarrhea in immunosuppressed patients, and postinfectious irritable bowel syndrome also have been reported in association with norovirus infection (23--25
); however, more data from analytic studies are needed to confirm a causal link with these conditions.
norovirus is shed primarily in the stool but also can be found in the vomitus of infected persons, although it is unclear if detection of virus alone indicates a risk for transmission. the virus can be detected in stool for an average of 4 weeks following infection, although peak viral shedding occurs 2--5 days after infection, with a viral load of approximately 100 billion viral copies per gram of feces (26
). however, given the lack of a cell culture system or small animal model for human norovirus, whether these viruses represent infectious virus is unknown, and therefore the time after illness at which an infected person is no longer contagious also is unknown. furthermore, up to 30% of norovirus infections are asymptomatic, and asymptomatic persons can shed virus, albeit at lower titers than symptomatic persons (26--28
). the role of asymptomatic infection in transmission and outbreaks of norovirus remains unclear.
long-term care and other health-care facilities
health-care facilities including nursing homes and hospitals are the most commonly reported settings of norovirus outbreaks in the united states and other industrialized countries (59,60,63--65
). virus can be introduced from the community into health-care facilities by staff, visitors, and patients who might either be incubating or infected with norovirus upon admission or by contaminated food products. outbreaks in these settings can be prolonged, sometimes lasting months (66
). illness can be more severe in hospitalized patients than for otherwise healthy persons (18
), and associated deaths have been reported (21,22
). strict control measures (including isolation or cohorting of symptomatic patients, exclusion of affected staff, and restricting new admissions into affected units) are disruptive and costly but might be required to curtail outbreaks (9,67,68
link to the full cdc guidelines:
the attached file is the full updated guidelines in pdf format for easy printing.