NORWALK VIRUS
Presented by:
Andrea Riley
Sharon Widjaja
Jessica Bell
Introduction
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First discovered in diarrheal stool specimens
from school children in Norwalk, Ohio in
1968 during an epidemic of gastroenteritis
Renamed Norovirus in 2002 by the
International Committee on Taxonomy of
Viruses
Family: Caliciviridae
Genus: Norovirus
Symptoms: acute gastroenteritis
Classification
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Baltimore classification: Class IV
(+) ssRNA
Non-enveloped
40 different strains within the genus
5 genogroups based on sequence similarity
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human pathogens in genogroups I, II and IV
Tropism - Small intestines
Structure
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27-35 nm in diameter
Icosahedral symmetry
composed of 90 dimers of
the capsid protein
3 ORFs
- 1st encodes polyprotein
- 2nd encodes capsid
proteins
- 3rd encodes other
proteins of unknown fxns
Pathogenesis
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Entry - oral ingestion
Multiplication - small intestine (can cause transient lesions of intestinal
mucosa)
o damage of microvilli (blunted villi with intact mucosa and epithelial)
o damaged epithelial cells causes malabsorption and enzymatic disorder lead to diarrhea
o "virus-mediated changes in gastric motility and delayed gastric emptying" leads to vomiting
Exit - shed in feces (up to 3 weeks)
Pathogenesis cont'd
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Binds to histo-blood group antigens
o HBGAs are complex carbohydrates on RBCs,
mucosal epithelia, saliva, milk and other body
fluids
o Polymorphism of HGBAs are defined by their
Lewis, secretor, and ABO types
o Norovirus targets gastrointestinal epithelial
cells
o Three distinct antigens - A, B, and O
P2 domain of viral capsid recognizes these antigens
at their terminal furose
Different strains of noroviruses are likely to
recognize different antigens
o Genogroup I noroviruses preferentially
recognize blood group antigens A and O.
o Genogroup II noroviruses preferentially
recognize blood group antigens A and B.
Transmission
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Fecal-oral route
Contaminated food and water consumption
Body fluid of infected person:
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Vomitus
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aerosolization
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one single vomiting incident may
produce an estimated 30 million viral
particles
Feces (found in stool up to 3 weeks
after recovery from symptoms)
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at the peak of an enteric virus infection,
more than 1011 virions per gram may be
excreted in the stool
Highly contagious - as few as 10 fomites can cause
infection
Non-enveloped viruses remain viable longer on
surfaces than enveloped viruses
Epidemiology
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Accounts for more than 96% of viral gastroenteritis
cases in the U.S alone.
Nearly 50% of all acute, infectious nonbacterial
gastroenteritis cases in the United States
Usually lasted for 24-72 hours.
All ages
Rare deaths
o immunocompromised, infants
elderly
Higher rate of transmissibility
in populations in close contact
Norwalk Virus vs Rotavirus
Norwalk virus
+ssRNA of Caliciviridae family, nonenveloped
All ages
Nausea and vomiting
Diarrhea
Abdominal cramps
Rotavirus
dsRNA of Reoviridae family, nonenveloped
Mostly in young infants, rarely in
adults
Excess dehydration
Diarrhea + dry/ sticky mucosa
present
Weight loss
Norwalk Virus vs Rotavirus
Norwalk Virus
Rotavirus
Virus shedding up to 3 weeks postrecovery
Virus shedding up to 10 days since
onset of symptoms
Rare deaths
(immunocompromised, infants)
Deaths due to dehydration
Symptoms develops within 24-48
hrs from ingestion.
No vaccines
Symptoms develops within 2 days of
exposure
Vaccines available
Case Study
Several adults complained of
serious diarrhea, nausea,
vomiting, and a mild fever
2 days after visiting Le Cafe'
Grease. The symptoms
were too severe to result
from food poisoning or a
routine gastroenteritis, but
lasted only 24 hours.
Diagnosis
DDx: staph aureus, campylobacter, shigella, salmonella, escherichia coli,
clostridium difficile, enterovirus, norovirus
Check for virus in stool samples and vomitus
Antibodies detection in serum samples by immune electron
microscope and immunoassay techniques
Real-time PCR on stool or vomitus samples
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Treatment and Medication
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Usually runs its course in 1-2 days
Stay hydrated with water and electrolytes
Avoid sugary beverages (worsen diarrhea)
Intravenous fluids and electrolyte resuscitation if
nausea is too severe.
Antiperistaltic agents for
patients with severe
diarrhea, but not
recommended for infectious
diarrhea.
Symptoms usually resolves
by itself within 24- 48 hours.
Prevention
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No vaccine at this time, but active
field of research!
WASH HANDS! Especially after
bathroom usaged
Identification of contaminated
sources
Sanitization and disinfection of
contaminated sites
Strict hygiene monitoring of food
handlers
Water supplies should be
protected from the risk of
contamination from sewage
Education
References
Blacklow NR. Norwalk Virus and Other Caliciviruses. In: Baron S, editor. Medical Microbiology. 4th edition.
Galveston (TX): University of Texas Medical Branch at Galveston; 1996. Chapter 65. Available from:
http://www.ncbi.nlm.nih.gov/books/NBK8545/
Boone SA, Gerba CP. 2007. Significance of fomites in the spread of respiratory and enteric viral disease. Appl.
Environ. Microbiol. 73: 1687–1696
Huang P, Farkas TM, Marionneau S, et al. Noroviruses bind to human ABO, Lewis, and secretor histo-blood
group antigens: identification of 4 distinct strain-specific patterns. J Infect Dis 2003 Jul 1;188(1):19-31
Khan, Zartash Zafar, MD, Mark Martin Huycke, MD, Todd S. Wills, MD, and Michelle A. Jaworski, MD. "Norwalk
Virus." Medscape.com. WebMD Health Professional Network, 11 Jan. 2012. Web. 18 Oct. 2012.
<http://emedicine.medscape.com/article/224225-overview>.
Nguyen, David D., Sally Henin Awad, and Brent R. King. "Rotavirus." Medscape.com. WebMD Health
Professional Network, 2012. Web. 18 Oct. 2012. <http://emedicine.medscape.com/article/803885overview>.
"Norovirus." Centers for Disease Control and Prevention. Centers for Disease Control and Prevention, 12 Apr.
2012. Web. 18 Oct. 2012. <http://www.cdc.gov/norovirus/about/index.html>.
Prasad B. V., Rothnagel R, Jiang X, Estes M.K. (1994). Three-dimensional structure of baculovirus-expressed
Norwalk virus capsids. J. Virol 68, 5117-5125. Website:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC236455/
"Viral Gastroenteritis." Viral Gastroenteritis. Ed. A.D.A.M. U.S. National Library of Medicine, 18 Nov. 0000. Web.
18 Oct. 2012. <http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001298/>.