Norovirus Infection – Clinical Signs, Transmission and Prevention
Sanjana1, Nancy Jasrotia1*, Komal1 and Ayush Ranjan2
1PhD Scholar, ICAR-IVRI, Bareilly
2MVSc Scholar, BVC, BASU, Patna
Abstract
Norovirus, a RNA virus belongs to the family Caliciviridae, is a human enteric pathogen that causes substantial morbidity across both health care and community settings. The ease of transmission, very low infectious dosage, brief incubation period, environmental persistence, and the lack of long-lasting immunity after infection enables the rapid transmission of norovirus in confined populations. Norovirus infections are an issue of concern in both high- and low-income nations. Norovirus is estimated to cost $60 billion annually in lost productivity and medical expenses worldwide. The prompt implementation of infection control measures remains to be the cornerstone of outbreak management of norovirus.
Introduction
Noroviruses (genus Norovirus, family Caliciviridae) belong to a group of related, ssRNA, non-enveloped viruses that are known to cause acute gastroenteritis in humans. Norovirus which were previously described as “Norwalk-like viruses” has been given the official genus name.
Currently, human noroviruses belong to one of three norovirus genogroups (GI, GII, or GIV), which are further divided into >25 genetic clusters. Over 75% of confirmed human norovirus infections are associated with genotype GII. Noroviruses are highly contagious, with as few as 18 virus particles thought to be sufficient to cause infection. This pathogen is estimated to be the causative agent in over 21 million gastroenteritis cases every year in the United States, representing approximately 60% of all acute gastroenteritis cases from known pathogens.
Clinical Signs
Norovirus-associated gastroenteritis typically takes 12 to 48 hours to develop, with a median time of about 33 hours. The symptoms of illness include nausea, acute-onset vomiting, watery, non-bloody diarrhoea, and abdominal pain. Additionally, headache, malaise, and myalgia are frequently observed. In nearly half of cases, low grade fever is present. The most frequent complication, dehydration, may call for intravenous fluid replacement. Typically, symptoms persist 24 to 60 hours. Up to 30% of illnesses could not show any symptoms. Most commonly the outbreaks are seen from November and April.
Transmission
Noroviruses are primarily spread orally, either directly from person to person or through contaminated food or drink. Additionally, vomitus can act as a droplet source for noroviruses to disseminate. These viruses can withstand temperatures of up to 60°C (140°F) and are comparatively robust in the environment. In healthcare facilities, transmission can also occur through hand transfer of the virus to the oral mucosa via contact with materials, fomites, and environmental surfaces that have been contaminated with either faeces or vomitus. Although all age groups are affected with norovirus infections, however, older people are more prone to experience severe consequences and prolonged sickness.
Diagnosis
Diagnosis of norovirus infection relies on the detection of viral RNA in the stools of affected persons, by use of reverse transcription-polymerase chain reaction (RT-PCR) assays. Enzyme immune-assays may also be used to detect norovirus outbreaks, however they are not advised for use in patient diagnosis. Although positive findings can be achieved using RT-PCR on samples taken as long as 7 days after the onset of symptoms, stool specimens collected within 48 to 72 hours after the onset of symptoms are the best for viral identification. A clinical diagnosis of norovirus infection is frequently made because rapid and routine laboratory testing procedures are not always readily available, especially after other causes of gastroenteritis have been ruled out.
Prevention and Control
There is currently no vaccine available for norovirus and, generally, no specific medical treatment is offered for norovirus infection apart from oral or intravenous repletion of volume.
Patients with suspected norovirus infections may be housed in private rooms or shared rooms with other patients who have the same infection in a healthcare facility. Additional precautions can reduce the possibility of coming into contact with noroviruses in healthcare facilities:
- Use of gloves and gowns while attending or interacting with patients exhibiting norovirus symptoms
- Following hand-hygiene guidelines
- Cleaning and disinfection of high-touch patient surfaces and equipment with an EPA-approved product that has a label claim for norovirus
- Discard of infected clothing and linens
- Isolation, cohorting (grouping of patients on the basis of symptoms) and exclusion of symptomatic staff, patients and visitors
References
Barclay, L., Park, G. W., Vega, E., Hall, A., Parashar, U., Vinjé, J., & Lopman, B. (2014). Infection control for norovirus. Clinical microbiology and infection : the official publication of the European Society of Clinical Microbiology and Infectious Diseases, 20(8), 731–740.
Villabruna, N., Koopmans, M., & de Graaf, M. (2019). Animals as Reservoir for Human Norovirus. Viruses, 11(5), 478.
