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| [[Image:Norwalk virus.jpg|thumb|Norwalk virus]] | | __NOTOC__ |
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| | | [[Norovirus infection resident survival guide|'''Resident'''<br>'''Survival'''<br>'''Guide''']] |
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| == Overview == | | {{About1|Norovirus}} |
| | '''For patient information click [[{{PAGENAME}} (patient information)|here]]''' |
| | {{Infobox_Disease | |
| | Name = Norovirus infection| |
| | Image = Norwalk virus.jpg| |
| | Caption = Norwalk virus| |
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| | {{Norovirus infection}} |
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| Noroviruses are a group of viruses that cause the “stomach flu,” or gastroenteritis (GAS-tro-en-ter-I-tis), in people. The term norovirus was recently approved as the official name for this group of viruses.
| | {{SK}} Norovirus; Norwalk virus; Norwalk-like virus; NoV; NV; NLV; Norwalk-like virus infection; Norwalk virus infection; Small round structured virus; SRSV; Sapporo virus; Snow mountain virus; SMV; Stomach flu; Winter vomiting disease; Winter vomiting bug |
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| | ==[[Norovirus infection overview|Overview]]== |
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| '''''Related Key Words and Synonyms:'''''
| | ==[[Norovirus infection historical perspective|Historical Perspective]]== |
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| Norwalk-like viruses (NLVs), caliciviruses (because they belong to the virus family Caliciviridae), small round structured viruses.
| | ==[[Norovirus infection classification|Classification]]== |
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| == Epidemiology and Demographics == | | ==[[Norovirus infection pathophysiology|Pathophysiology]]== |
| '''Who gets norovirus infection?'''
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| Anyone can become infected with these viruses. There are many different strains of norovirus, which makes it difficult for a person’s body to develop long-lasting immunity. Therefore, norovirus illness can recur throughout a person’s lifetime. In addition, because of differences in genetic factors, some people are more likely to become infected and develop more severe illness than others.
| | ==[[Norovirus|Causes]]== |
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| '''Surveillance of Norovirus Infection in the United States'''
| | ==[[Norovirus infection differential diagnosis|Differentiating Norovirus infection from other Diseases]]== |
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| CDC currently does not conduct active surveillance to monitor outbreaks of gastroenteritis caused by noroviruses. Outbreaks are reported to CDC's Viral Gastroenteritis Section, Respiratory and Gastroenteric Viruses Branch, Division of Viral Diseases, National Center for Immunization and Respiratoiry 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.
| | ==[[Norovirus infection epidemiology and demographics|Epidemiology and Demographics]]== |
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| == Risk Factors == | | ==[[Norovirus infection risk factors|Risk Factors]]== |
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| == Screening == | | ==[[Norovirus infection natural history, complications and prognosis|Natural History, Complications and Prognosis]]== |
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| == Pathophysiology & Etiology== | | ==Diagnosis== |
| Noroviruses (genus Norovirus, family Caliciviridae) are a group of related, single-stranded RNA, nonenveloped viruses that cause acute gastroenteritis in humans. Norovirus was recently approved as the official genus name for the group of viruses provisionally described as “Norwalk-like viruses” (NLV).
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| Noroviruses are members of a group of viruses called caliciviruses also known previously as “Norwalk-like viruses.” Infection with norovirus affects the stomach and intestines, causing an illness called gastroenteritis, or “stomach flu.” This “stomach flu” is not related to the flu (or influenza), which is a respiratory illness caused by influenza virus. In addition, noroviruses are not related to bacteria and parasites that can cause gastrointestinal illnesses. Norovirus is not a “new” virus, but interest in it is growing as more is learned about how frequently noroviruses cause illness in people
| | [[Norovirus infection diagnostic study of choice]] | [[Norovirus infection history and symptoms|History and Symptoms]] | [[Norovirus infection physical examination|Physical Examniation]] | [[Norovirus infection laboratory findings|Laboratory Findings]] |
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| | ==Treatment== |
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| '''Transmission'''
| | [[Norovirus infection medical therapy|Medical Therapy]] | [[Norovirus infection primary prevention|Primary Prevention]] | [[Norovirus infection secondary prevention|Secondary Prevention]] | [[Norovirus infection cost-effectiveness of therapy|Cost-Effectiveness of Therapy]] | [[Norovirus infection future or investigational therapies|Future or Investigational Therapies]] |
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| Noroviruses are transmitted primarily through the fecal-oral route, either by consumption of fecally contaminated food or water or by direct person-to-person spread. Environmental and fomite contamination may also act as a source of infection. Good evidence exists for transmission due to aerosolization of vomitus that presumably results in droplets contaminating surfaces or entering the oral mucosa and being swallowed. No evidence suggests that infection occurs through the respiratory system.
| | ==Case Studies== |
| | [[Norovirus infection case study one|Case #1]] |
| | ==Related Chapters== |
| | *[[Gastroenteritis]] |
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| Noroviruses are highly contagious and as few as 10 viral particles may be sufficient to infect an individual. During outbreaks of norovirus gastroenteritis, several modes of transmission have been documented; for example, initial foodborne transmission in a restaurant, followed by secondary person-to-person transmission to household contacts. Although presymptomatic viral shedding may occur, shedding usually begins with onset of symptoms and may continue for 2 weeks after recovery. It is unclear to what extent viral shedding over 72 hours after recovery signifies continued infectivity.
| | ==External Links== |
| | * CDC information on Norovirus infection [http://www.cdc.gov/norovirus/index.html] |
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| '''What is the name of the illness caused by noroviruses?'''
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| Illness caused by norovirus infection has several names, including:
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| *stomach flu – this “stomach flu” is not related to the flu (or influenza), which is a respiratory illness caused by influenza virus.
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| *viral gastroenteritis – the most common name for illness caused by norovirus. Gastroenteritis refers to an inflammation of the stomach and intestines.
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| *acute gastroenteritis
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| *non-bacterial gastroenteritis
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| *food poisoning (although there are other causes of food poisoning)
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| *calicivirus infection
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| == Molecular Biology ==
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| == Genetics ==
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| == Natural History ==
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| == Diagnosis ==
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| '''Human.''' In the last 10 years, diagnosis of norovirus as cause of outbreaks of acute gastroenteritis has improved with the increasing use of the reverse transcriptase polymerase chain reaction (RT-PCR). Currently, state public health laboratories of 47 states have the capability to test for noroviruses by (realtime) RT-PCR. RT-PCR detects the norovirus RNA and can be used to test stool and emesis samples, as well as environmental swabs in special studies. Identification of the virus can be best made from stool specimens taken within 48 to 72 hours after onset of symptoms, although good results can be obtained by using RT-PCR on samples taken as long as 5 days after symptom onset. Virus can sometimes be found in stool samples taken as late as 2 weeks after recovery.
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| Sequencing of norovirus strains found in clinical and environmental samples has greatly helped in conducting epidemiologic investigations by linking cases to each other and to a common source and by differentiating outbreaks that were mistakenly connected. Sequences can be entered into CaliciNet, a recently developed sequence database on the basis of the PulseNet model. In the next years CaliciNet will be further implemented to be able to help to determine links (e.g., norovirus contaminated foods) between outbreaks across the U.S.
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| === Differential Diagnosis ===
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| === History and Symptoms ===
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| The incubation period for norovirus-associated gastroenteritis in humans is usually between 24 and 48 hours (median in outbreaks 33 to 36 hours), but cases can occur within 12 hours of exposure. Norovirus infection usually presents as acute-onset [[vomiting]], watery non-bloody [[diarrhea]] with [[abdominal cramps]], and [[nausea]]. Low-grade fever also occasionally occurs, and vomiting is more common in children. [[Dehydration]] is the most common complication, especially among the young and elderly, and may require medical attention. Symptoms usually last 24 to 60 hours. Recovery is usually complete and there is no evidence of any serious long-term sequelae. Studies with volunteers given stool filtrates have shown that asymptomatic infection may occur in as many as 30% of infections, although the role of asymptomatic infection in norovirus transmission is not well understood.
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| === Physical Examination ===
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| ==== Appearance of the Patient ====
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| ====Vital Signs====
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| ====Skin====
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| ==== Eyes ====
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| ==== Ear Nose and Throat ====
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| ==== Heart ====
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| ==== Lungs ====
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| ==== Abdomen ====
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| ==== Extremities ====
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| ==== Neurologic ====
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| ==== Other ====
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| === Laboratory Findings ===
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| Older methods for diagnosis include direct and immune electron microscopy of fecal specimens, and detection of a fourfold increase of specific antibodies in acute- and convalescent-phase blood samples. Several commercially available enzyme-linked immunosorbent assays for detection of virus in stools have been developed but await evaluation further evaluation regarding sensitivity and specificity.
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| ==== Electrolyte and Biomarker Studies ====
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| ==== Electrocardiogram ====
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| ==== Chest X Ray ====
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| ==== MRI and CT ====
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| ==== Echocardiography or Ultrasound ====
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| ==== Other Imaging Findings ====
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| === Other Diagnostic Studies ===
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| In addition to microbiological techniques, several epidemiologic criteria have been proposed for use in determining whether an outbreak of gastroenteritis is of viral origin. Kaplan's criteria for this purpose are as follows: 1) a mean (or median) illness duration of 12 to 60 hours, 2) a mean (or median) incubation period of 24 to 48 hours, 3) more than 50% of people with vomiting, and 4) no bacterial agent previously found. Although quite specific, these criteria are not very sensitive, and therefore the possibility of a viral etiology should not be discarded if the criteria are not met.
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| '''Environmental.''' Methods to recover and detect virus in food need to be adapted for each food substance; these have been only rarely used, with the exception of assays to detect virus in shellfish. Drinking water can be tested for noroviruses by using RT-PCR when large (10-100 L) volumes of water are processed through specially designed filters.
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| == Risk Stratification and Prognosis==
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| == Treatment ==
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| === Pharmacotherapy ===
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| ==== Acute Pharmacotherapies ====
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| ==== Chronic Pharmacotherapies ====
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| === Primary Prevention ===
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| Prevention of foodborne norovirus disease is based on the provision of safe food and water. Noroviruses are relatively resistant to environmental challenge: they are able to survive freezing, temperatures as high as 60°C, and have even been associated with illness after being steamed in shellfish. Moreover, noroviruses can survive in up to 10 ppm chlorine, well in excess of levels routinely present in public water systems.
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| Despite these features, it is likely that relatively simple measures, such as correct handling of cold foods, strict hand washing after using the bathroom and before handling food items, and paid sick leave, may substantially reduce foodborne transmission of noroviruses.
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| Prevention of norovirus disease spread via droplets from vomitus (person to person transmission) should focus on methods to limit transmission including isolation precautions (e.g., cohort sick patients in a healthcare facility) and environmental disinfection.
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| === Secondary Prevention ===
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| === Cost-Effectiveness of Therapy ===
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| === Future or Investigational Therapies ===
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| =="The Way I Like To Do It ..." Tips and Tricks From Clinicians Around The World==
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| ===Suggested Revisions to the Current Guidelines===
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| ==References==
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| #http://www.cdc.gov/ncidod/dvrd/revb/gastro/norovirus.htm
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| #http://www.cdc.gov/ncidod/dvrd/revb/gastro/norovirus-qa.htm
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| #http://www.cdc.gov/ncidod/dvrd/revb/gastro/norovirus-factsheet.htm
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| #http://en.wikipedia.org/wiki/Norovirus
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| == Acknowledgements ==
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| The content on this page was first contributed by: C. Michael Gibson, M.S., M.D.
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| Initial content for this page in some instances came from [http://www.wikipedia.org Wikipedia]
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| '''List of contributors:'''
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| Pilar Almonacid
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| == Suggested Reading and Key General References ==
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| == Suggested Links and Web Resources ==
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| == For Patients ==
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| [[Category:DiseaseState]]
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| [[Category:Infectious disease]] | |
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