Norovirus infection secondary prevention
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
The CDC currently does not conduct active surveillance to monitor outbreaks of gastroenteritis caused by noroviruses. The National Outbreak Reporting System (NORS) is a web-based system that was launched by the CDC in 2009 to collect information on outbreaks of foodborne, waterborne, and enteric diseases that spread from person-to-person, animals, environmental surfaces, and other or unknown ways. Public health agencies can report all outbreaks of gastroenteritis, including norovirus illness. The CDC also developed CaliciNet in 2009. It is a network of public health and food regulatory laboratories that submit norovirus sequences identified from outbreaks into a national database.
Secondary Prevention
The CDC currently does not conduct active surveillance to monitor outbreaks of gastroenteritis caused by noroviruses. Outbreaks are reported to the CDC's Viral Gastroenteritis Section, Respiratory and Gastroenteric Viruses Branch, Division of Viral Diseases, National Center for Immunization and Respiratory Diseases (NCIRD) when states send specimens for testing or sequencing, or outbreaks are reported directly by states to the electronic database (eFORS) maintained by the Foodborne Diarrheal Diseases Branch.
Reporting
Currently, state, local, and territorial health departments are not required to report individual cases of norovirus illness to a national surveillance system. They may not know about such cases because most hospitals and doctor’s offices do not have capability to test for norovirus. The virus is usually diagnosed only when an outbreak happens.
Health care providers should report all outbreaks of acute gastroenteritis, including suspected outbreaks of norovirus, to the appropriate state, local or territorial health department.
Definition of a Norovirus Outbreak
An outbreak of norovirus is defined as an occurrence of two or more similar illnesses resulting from a common exposure. Health departments are encouraged to report all suspected and confirmed norovirus outbreaks through the National Outbreak Reporting System (NORS) and CaliciNet.
Surveillance Systems
NORS
NORS was launched by the CDC in 2009 to collect information on outbreaks of foodborne, waterborne, and enteric diseases that spread from person-to-person, animals, environmental surfaces, and other or unknown ways. Public health agencies can report all outbreaks of gastroenteritis, including norovirus illness, through this web-based system. This information is used to determine where norovirus outbreaks commonly occur, how the virus is spread, and specific food or water sources involved. In turn, this helps with identifying the best ways to prevent and control norovirus illness and outbreaks.
CaliciNet
The CDC developed CaliciNet in 2009. It is a network of public health and food regulatory laboratories that submit norovirus sequences identified from outbreaks into a national database. The information is used to link norovirus outbreaks that may be caused by common sources (such as food), monitor trends, and identify emerging norovirus strains. As of February 2012, public health laboratories in 25 states have been certified by the CDC to participate in CaliciNet. States that are not yet certified may contribute through designated CaliciNet outbreak support centers, including the the CDC.
Other Surveillance Systems
The CDC is using the New Vaccine Surveillance Network (NVSN) and the Fooborne Diseases Active Surveillance Network (FoodNet) to perform norovirus testing on patients with gastroenteritis. This will help generate new estimates of norovirus illness and monitor trends over time.
Responding to Norovirus Outbreaks
Prompt response, investigation, and reporting of norovirus outbreaks are critical for identifying causes of outbreaks and the primary mechanisms by which the virus spreads. Collection of appropriate specimens also depends on a rapid response.
Typical Responsibilities During an Outbreak
State, Local, and Territorial Health Departments
- Serve as the lead agencies in most investigations of norovirus outbreaks
- Interview patients, collect stool specimens, and may perform diagnostic testing
Food Regulatory Agencies (FDA, USDA, and State Authorities)
- Collaborate with health departments when a link between contaminated food and illness are identified
- Perform food testing for specific foods, such as shellfish
- Coordinate recalls of foods involved in outbreaks
The CDC Helps With Investigations and Control of Norovirus Outbreaks by:
- Coordinating multi-state outbreak investigations
- Providing epidemiologic consultation and tools
- Testing specimens and providing other laboratory support
Using Kaplan Criteria for Suspected Norovirus Outbreaks
When it is not possible to get laboratory confirmation of norovirus, health departments can use Kaplan Criteria to determine if the outbreak was likely caused by norovirus.
The Kaplan Criteria are:
- A mean (or median) illness duration of 12 to 60 hours
- A mean (or median) incubation period of 24 to 48 hours
- More than 50% of people with vomiting
- No bacterial agent found.
When all four criteria are present, it is very likely that the outbreak was caused by norovirus. However, about 30% of norovirus outbreaks do not meet these criteria. If the criteria are not met, it does not mean that outbreak was not caused by norovirus.
Outbreak on Cruises
Recommendations for Cruise Staff Members
- Implement additional disinfection measures and cleaning procedures.
- Advise passengers and crew who are ill to stay in their cabins until they are well for 24 hours after their last episode of diarrhea or vomiting.
- Report numbers of cases of illness to CDC on a daily basis.
- Discontinue certain high-risk activities during a cruise.
Role of Vessel Sanitation Program
VSP monitors and evaluates GI illnesses aboard ships to determine the cause of the outbreaks and to make recommendations for control. It takes following steps to accomplish the goal.
- Estimates the magnitude of GI illnesses among passengers and crew.
- Monitors the spread and distribution of GI illnesses among both passengers and crew members.
- Assists in assessment of changes in sanitation practices, infectious agents, and types of diseases.
- Evaluates the effectiveness of prevention and control strategies.
- Provides lab support to confirm the cause of the illness.