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 Norovirus aka Norwalk

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Libelle
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PostSubject: Norovirus aka Norwalk   Sun 26 Feb 2012, 6:32 am

Sooooo...yeah. Hubby and I have been sick this week with norovirus. we weren't on a cruise, anywhere deemed 'risky' or eating poo (well, I wasn't, anyway) Razz

Apparently our town is having an outbreak, and the bordering city Fredericton is now experiencing it as well. The only 'out of the norm' things we did in the days preceding his infection were sit in damn H&R Block for 3 hours and go shopping in Presque Isle, ME for a day (Monday). I got home at 1am tuesday and he was sick as I have ever seen him. 15 hrs later I was sick.

Seriously people, if you think you have a stomach bug, stay home!! Stay hydrated!!! It hits fast and moves out fast but you shed the virus for 3-4 days after the symptoms stop. Just a friendly whiny PSA Embarassed

From the CDC, since I can't post links yet...lol


Norovirus: Technical Fact Sheet
Viral Gastroenteritis > Norovirus > Technical Fact Sheet
Noroviruses are a group of related, single-stranded RNA, non-enveloped viruses that cause acute gastroenteritis in humans. Norovirus is the official genus name for the group of viruses previously described as “Norwalk-like viruses” (NLV) or small round structured viruses (SRSVs) because of their morphologic features. Noroviruses are part of the larger Caliciviridae family, which also includes the genus Sapovirus, formerly described as “Sapporo-like viruses” (SLV) and sometimes referred to as classic or typical caliciviruses, which also cause gastroenteritis in humans.

Noroviruses are named after the original strain “Norwalk virus,” which caused an outbreak of gastroenteritis in a school in Norwalk, Ohio, in 1968. Currently, there are five recognized norovirus genogroups, of which three (GI, GII, and GIV) are known to affect humans. More than 25 different genotypes have been identified within these genogroups. And since 2002, variants of the GII.4 genotype have been the most common cause of norovirus outbreaks.

Clinical Presentation

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 diarrhea is more common than vomiting in children. Dehydration is the most common complication, especially among the young and elderly, and may require medical attention. Symptoms usually last 24 to 72 hours. Recovery is usually complete and there is no evidence of any serious long-term sequelae. Studies with volunteers given the virus 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.



Virus Transmission

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.

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 pre-symptomatic viral shedding may occur, shedding usually begins with onset of symptoms and may continue for 2 weeks or more after recovery. It is unclear to what extent viral shedding over 72 hours after recovery signifies continued infectivity.

Immunity to Norovirus

Mechanisms of immunity to norovirus are unclear. It appears that immunity may be strain-specific and lasts only a few months; therefore, given the genetic variability of noroviruses, individuals are likely to be repeatedly infected throughout their lifetimes. This may explain the high attack rates in all ages reported in outbreaks. Recent evidence also suggests that susceptibility to infection may be genetically determined.

Disease burden of Norovirus Gastroenteritis

In the United States, CDC estimates that more than 21 million cases of acute gastroenteritis each year are due to norovirus infection, and more than 50% of all foodborne disease outbreaks can be attributed to noroviruses.

Among the 232 outbreaks of norovirus illness reported to CDC from July 1997 to June 2000, 57% were foodborne, 16% were due to person-to-person spread, and 3% were waterborne; in 23% of outbreaks, the cause of transmission was not determined. Among these outbreaks, common settings included restaurants and catered meals (36%), nursing homes (23%), schools (13%), and vacation settings or cruise ships (10%).

Most foodborne outbreaks of norovirus illness are likely to arise though direct contamination of food by a food handler immediately before its consumption. Outbreaks have frequently been associated with consumption of cold foods, including various salads, sandwiches, and bakery products. Liquid items (e.g., salad dressing or cake icing) that allow virus to mix evenly are often implicated as a cause of outbreaks. Food can also be contaminated at its source, and oysters from contaminated waters have been associated with widespread outbreaks of gastroenteritis. Other foods, including raspberries and salads, have been contaminated before widespread distribution and subsequently caused extensive outbreaks.

Waterborne outbreaks of norovirus disease in community settings have often been caused by sewage contamination of wells and recreational water.



Diagnosis of Norovirus

Clinical diagnosis of norovirus in humans. Since 1990, diagnosis of norovirus as a 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 in all 50 states have the capability to test for noroviruses by (real-time) 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 obtained during the acute phase of illness (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, particularly with the increased sensitivity afforded by real-time RT-PCR assays.

Other 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. Commercial enzyme-linked immunosorbent assays for detection of virus in stools have been developed, although these tests currently exhibit inadequate sensitivity (<50%) to be useful for diagnosis of sporadic cases. However, in outbreak settings, these tests may be useful to rapidly identify norovirus as the likely etiology.

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 national network of public health laboratories that tracks the different sequences of norovirus that cause disease. This system allows rapid assessment of the relationships between strains and identification of new strains as they emerge.

Application of “Kaplan Criteria” in outbreaks. When microbiological confirmation of a suspected norovirus outbreak is not possible, the Kaplan Criteria may be applied to determine the likelihood that the outbreak is of viral origin. These criteria 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 found. The criteria are very specific—when all four criteria are present, there is a high likelihood that the outbreak is attributable to norovirus. However, the criteria lack sensitivity—about 30% of norovirus outbreaks do not meet these criteria. Therefore the possibility of a viral etiology should not be discarded if these criteria are not met.



Detection of norovirus in food and water. Methods to recover and detect norovirus 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.

Management of Norovirus Infection

No specific therapy exists for norovirus gastroenteritis. Symptomatic therapy consists of replacing fluid losses and correcting electrolyte disturbances through oral and intravenous fluid administration.

Prevention

The most important means of preventing norovirus transmission and infection is exercising frequent and appropriate hand washing. Alcohol-based hand sanitizers (≥62% ethanol) may be helpful as an adjunct method of hand hygiene, but should not replace washing with soap and water.

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.

Despite these features, it is likely that relatively simple measures, such as correct handling of cold foods, frequent hand washing and paid sick leave, may substantially reduce foodborne transmission of noroviruses.

Environmental surfaces that may be contaminated by norovirus should be disinfected using a chlorine bleach solution with a concentration of 1000-5000 ppm (5-25 tablespoons of household bleach [5.25%] per gallon of water) or other disinfectant registered as effective against norovirus by the Environmental Protection Agency (exit) [84 KB/11 pages]. Evidence for efficacy against norovirus is usually based on studies using feline calicivirus (FCV) as a surrogate. However, FCV and norovirus exhibit different physiochemical properties and it is unclear whether inactivation of FCV reflects efficacy against norovirus.
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PostSubject: Re: Norovirus aka Norwalk   Sun 26 Feb 2012, 9:47 am

Anywhere there are large groups of people you are going to get sick. It's because of the things we touch, doorknobs, shopping carts etc. The best remedy is wash your hands constantly or use hand sanitizers. I work at a kids camp and after the kids leave we wipe everything down with virox wipes, kills everything even the aids virus.

Then again there are the viruses that are airborne not much you can do about those ones, someone sneezes and lookout it's spread to everyone around you.

Hope you're feeling better soon!!!
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Libelle
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PostSubject: Re: Norovirus aka Norwalk   Mon 27 Feb 2012, 12:30 pm

We're all better now! I hope when I go back to work tonight I'm not the pariah Embarassed we shall see. Eric & I travel a lot and both work & play in public places etc. Neither of us has ever picked up something like this. I might wish this on my worst enemy
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PostSubject: Re: Norovirus aka Norwalk   Mon 27 Feb 2012, 6:58 pm

Good to hear you're feeling better. Last Friday, almost the whole office at work left home sick. I was one of the very few who didn't end up sick in an office of 400 people. :o
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PostSubject: Re: Norovirus aka Norwalk   Tue 28 Feb 2012, 12:14 am

Ewwwwww...good you are getting better. I am a germophobe...gloves are my friend. Smile Smile Smile
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