Noroviruses are a group of related, single-stranded RNA, nonenveloped viruses that are a major cause of acute gastroenteritis in humans.
The CDC has announced the availability of a new toolkit(www.cdc.gov) designed to help health care professionals control and prevent norovirus gastroenteritis outbreaks in health care settings.
According to the CDC(www.cdc.gov), noroviruses are the most common causes of epidemic gastroenteritis, "responsible for at least 50 percent of all gastroenteritis outbreaks worldwide and a major cause of foodborne illness." In the United States, an estimated 21 million illnesses attributable to norovirus infection occur each year.
The new toolkit(www.cdc.gov) complements the "Guideline for the Prevention and Control of Norovirus Gastroenteritis Outbreaks in Healthcare Settings"(www.cdc.gov) developed last year by the CDC's Healthcare Infection Control Practices Advisory Committee. The guideline is based on an evidence review that addresses the following questions:
No vaccine currently exists to prevent human norovirus infection, and there is no specific therapy available to treat it. However, a proof-of-concept study(www.nejm.org) recently reported in the New England Journal of Medicine (NEJM) builds on earlier research that showed a monovalent intranasal vaccine formulated using Norwalk virus (the prototype human norovirus) viruslike particles (VLPs) induced virus-specific serum antibodies in vaccine recipients.
The purpose of the NEJM study was to determine whether the vaccine could provide protection against illness after a homologous norovirus challenge.
The double-blind, multicenter study involved 98 patients, 77 of whom completed all phases of the study and were included in the final efficacy analysis. Patients initially were randomized to receive either two doses of an adjuvanted vaccine containing 100 micrograms of Norwalk virus VLPs or two doses of a placebo vaccine.
Study participants then underwent a Norwalk virus challenge consisting of oral administration of about 10 times the amount of virus required to infect 50 percent of individuals to whom it is administered.
The authors report that Norwalk virus-associated gastroenteritis occurred in 69 percent of placebo recipients compared with 37 percent of those who received the vaccine. Vaccination also reduced the relative frequency of Norwalk virus infection, with infection occurring in 82 percent of placebo recipients and 61 percent of vaccine recipients. Disease severity was reduced in those who received the vaccine compared with placebo recipients, and onset of illness was delayed. No vaccine-related severe adverse events occurred in either group during the study.
"This study shows that it may be possible to use a vaccination strategy to prevent norovirus disease," the authors concluded.
- What host, viral or environmental characteristics increase or decrease the risk of norovirus infection in health care settings?
- What are the best methods to identify an outbreak of norovirus gastroenteritis in a health care setting?
- What interventions best prevent or contain outbreaks of norovirus gastroenteritis in the health care setting?
Recommendations in the guideline are segmented into various topic areas, such as patient isolation and similar precautions, hand hygiene, personal protective equipment, diagnostics, staff leave, and environmental cleaning. Resources in the toolkit are intended to aid in carrying out many of the recommendations.
For example, a sample communication framework allows health care facilities to specify which departments are to provide what services in the event of a suspected or confirmed norovirus outbreak, as well as who the exact contacts are to get that process started.
Also included in the toolkit are
- a fact sheet that provides an overview of norovirus infections in health care facilities,
- a poster outlining what health care professionals should know about norovirus infection,
- a sample worksheet for reporting cases of norovirus gastroenteritis,
- a slide set describing the management of norovirus outbreaks in health care settings and
- a sample framework document that can be used to identify resources for specimen submission during an outbreak.
A related report published last year in Morbidity and Mortality Weekly Report, "Updated Norovirus Outbreak Management and Disease Prevention Guidelines(www.cdc.gov)" addresses control and prevention of outbreaks that occur outside health care facilities.
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