By Daniell Brown
Disease: Norovirus (previously known as the Norwalk-like viruses) Etiologic agent: Caliciviruses
The Norovirus was originally discovered in 1968 in an outbreak of gastroenteritis in an elementary school in Norwalk, Ohio, USA (6).
Transmission routes include: fecal to oral, person-to-person, fomites and air borne (1).Transmission occurs by direct transfer of the virus to oral mucosa via contact with contaminated persons, fomites, and environmental surfaces that have been contaminated with feces or vomit (3).
The most common reservoir for this virus is people and the environment. For this reason, the Norovirus can be found living on cruise ships, in day-care centers, restaurants, Nursing homes, and other close quarter places due to its hardy and highly contagious nature (5). The virus can also find residence in foods eaten raw (such as oysters and sushi) and water that has been contaminated (4).
General Characteristics and Virulence Mechanisms:
The Norovirus is sometimes referred to as food poisoning or the stomach flu; although the virus is not influenza (5).The Norovirus is a small, rounded, non-enveloped, single-stranded RNA, that measure from 27-35 nm. The Norovirus can be genogrouped; I, II, IV cause human infections, and it is the leading cause of food-borne illness in the U.S due to contaminated food (oysters, frozen raspberries) prepared by ill prepares or contaminated water supply(1). The virus causes inflammation of the stomach and large intestine lining and is a leading cause of gastroenteritis (5). The Norovirus is highly contagious and spreads rapidly through populations that are confined; as few as 18 virus particles can cause infection (3), which is also a contributing factor to the virus’s virulence. There is a short incubation period after exposure to the virus of 12-48 hours, and the period of illness generally last from 3-5 days (1). The virus can also survive extreme temperatures that range from freezing to hot (3). What makes this virus is especially virulent, is the infectious asymptomatic virus shedding which can persist for up to two weeks, and the virus can also survive temperatures up to 60°C, as well as chlorinated waters, permitting its spread in recreational and drinking water as well as in steamed shellfish (6). January through April is a high season for Norovirus activity (4).
Signs, Symptoms, and Diagnosis:
Once someone is exposed to the Norovirus, they will go from healthy to severely ill within a day to two (5). Signs and symptoms of the Norovirus can be characterized by nausea, acute- onset vomiting (more often in children), and watery non-bloody diarrhea with abdominal cramps. Also, myalgia, malaise, and headaches are commonly reported with a low grade fever in about half of the cases (3). The diarrhea and vomiting caused by the Norovirus can cause serious dehydration which is most common for the elderly and children who become infected. Symptoms of dehydration are: dizziness occurs when standing, dry mouth, and urination decreases (5). To diagnosis a person with the Norovirus a stool specimen is taken ideally within 48 to 72 hours after the symptoms began; however, samples taken as long as 7 days after symptoms can yield positive results. To confirm that someone has been infected with the Norovirus, a positive result for viral RNA is looked for by way of reverse transcription-polymerase chain reaction (RT-PCR) assays. The technology need to perform this test is found at the CDC and state public health laboratories. Also available is a serology, enzyme immune-assay may be used for identification of a Norovirus outbreak, but are not recommended for diagnosis of individuals (3). Although the Norovirus can be confirmed via test, diagnosis is generally made solely on symptoms (5).
Control/ Treatment and Prevention:
Like other viruses, the Norovirus cannot be treated with antibiotics and there is currently no antiviral drug that is effective (5) however, there is an antiviral medicine in early development (4). Likewise, there is no vaccine against the Norovirus currently on the market (3). LigoCyte Pharmaceuticals in Montana is actively testing a nasal spray vaccine in human volunteers. There is also a second research group being conducted through ASU, which is moving toward human trials with a nasal vaccine that is slightly different. There are hopes that the vaccine will be ready in a few years (4).
Due to a lack of treatment options, patients are instructed to drink plenty of fluid such as water, Gatorade, and for children Pedialyte. Drinks with high sugar content, alcohol, and caffeinated drinks are to be avoided because they can cause diarrhea to worsen (5).The use of intravenous fluids may be used but only in cases of severe dehydration (3).
An infected person can remain contagious from the moment they begin to feel ill to anywhere from 3 days to 2weeks- after they recover (4). Because of the lengthy contagious period and the ease of transmission prevention is vital. Good hygiene will greatly help lower your risk of infection, especially when you are in tight quarters with other people. It is important to wash your hands after using the restroom, changing a baby’s diaper, or before preparing food. Using warm water and soap for 15 seconds (minimum) or use of an alcohol based-hand sanitizer is effective in preventing illness. Wash thoroughly any raw fruit and vegetables before eating, also when eating shellfish it is vital to cook the shellfish to a proper temperature. If someone has been ill due to the Norovirus, they should not prepare food for at least two to three days after they have no more signs or symptoms. It is important to disinfect all surfaces with a mixture of chlorine bleach and after an illness in your household (5).
Current information local and global:
In October 2011, Williamson County had several confirmed cases of Norovirus which greatly affected Georgetown ISD who urged parents to keep their children home if they felt they may have the virus (2). In February 2012, the Northeast was hit hard by the Norovirus. Eighty-five students fell ill at George Washington University, 186 at Rider University, and 100 at Princeton University. Hundreds of elementary, middle and high schools students were victims of the Norovirus, along with passengers from 3 different cruise ships (4).
Currently more than 20 million Americans every year are affected by the Norovirus, causing 800 deaths due to dehydration (4). Worldwide, recent estimates of more than 1 million people have been hospitalized and 200,000 deaths (mostly of children under the age of 5) due to the Norovirus. In Beijing, China, infants had a seroprevalence rate of 41% at 7 months of age, 65% at 1 year, 85% at 3 years, and 100% at 8-9 years of age. The role that the Norovirus plays in developing countries has yet to be firmly established. However, in many Asian and African countries, most children appear to acquire serum antibodies to the virus early in life, which suggest that the virus probably plays a pre-eminent role in pediatric diarrheal diseases seen in developing countries (6).
1. Auwaerter, Paul G. and Pham, Paul A. Johns Hopkins ABX Guide: Diagnosis and Treatment of Infectious Diseases. Jones and Bartlett Publishers. 2010.eBook (EBSCO host). 2nd ed. 869p.Web. 27 Apr. 2012.http://search.ebscohost.com/login.aspx?direct=true&db=nlebk&AN=337343&site=ehost-live
2. Case of the Norovirus Confirmed in Williamson County. Fox 7 News Austin. 04 Oct 2011. Web. 05 May 2012. http://www.myfoxaustin.com/dpp/news/local/Norovirus-Confirmed-in-Williamson-Co.20111004-ktbcw#axzz1uDFzsPMp.
3. CDC: “Norovirus in Healthcare Facilities Fact Sheet”. CDC. (2011). Web. 27 Apr. 2012. www.cdc.gov/hai/pdfs/norovirus/229110-ANoroCaseFactSheet508.pdf
4. Manning, Annita. “Nasty, Contagious Norovirus is Now ‘Everywhere’ ”. USA Today. 22 Feb. 2012. Web. 4 May 2012. http://www.usatoday.com/news/health/story/health/story/2012-02-22/Nasty-contagious-norovirus-is-everywhere-now/53211908/1
5. Norovirus: Symptoms and Treatment. Children’s Health Web MD. WebMD.com. 02 Apr. 2010. Web. 28 Apr. 2012. http://children.webmd.com/norovirus-symptoms-and-treatment?page=2&print=true
6. Diarrhoel Diseases. Initiative for Vaccine Research. WHO.(2009).Web. 27 Apr. 2012.http://www.who.int/vaccine_research/diseases/diarrhoeal/en/index1.html