Download norovirus: the stomach bug

NOROVIRUS: THE STOMACH BUG
Noroviruses are a highly contagious type of virus that
are the most common cause of foodborne illness and
acute gastroenteritis (swelling of the stomach or
intestines) around the world. Often called food poisoning, the stomach flu, or a
stomach bug, norovirus infection causes stomach
pain, vomiting, and diarrhea that usually lasts 1-3
days in adults. In children, the elderly, or people
with compromised immune systems due to chronic
conditions such as HIV, or from chemotherapy,
norovirus infection can be devastating and symptoms
can last as long as 4-6 days.
Anyone can become infected with
norovirus
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Norovirus infection is the leading cause of acute
gastroenteritis in adults and the second leading
cause in children worldwide.
Norovirus causes approximately one in five cases
of acute gastroenteritis in developed countries.
In developing countries, where other bacterial,
parasitic, and viral causes of gastroenteritis are
more prevalent, norovirus is responsible for
approximately one in six cases of acute
gastroenteritis and between 50,000 and 200,000
child deaths annually.
Noroviruses are extremely contagious
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Noroviruses spread easily and quickly through
direct contact with an infected person, or
through contact with contaminated food, water,
objects or surfaces.
It takes very few virus particles (fewer than 100)
to become infected.
Once infected, people shed the virus in vast
quantities in their stool and vomit.
While symptoms generally start 12-48 hours after
infection, a person can be contagious before
Electron micrograph of norovirus in stool
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There are many strains of norovirus and
new strains evolve constantly
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GVN Norovirus Experts:
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Cristiane Wobus, PhD. GVN Affiliate and
Associate Professor, Department of
Microbiology and Immunology, University of
Michigan Medical School
John Treanor, MD. GVN Center of Excellence
Director and Chief of the Department of
Medicine, Infectious Diseases, University of
Rochester Medical Center
Heinz Ellerbrok, PhD. Deputy Head, Center
for Biological Safety, Robert Koch Institute,
Berlin, Germany
symptoms begin and for days after symptoms
resolve.
Because they are so contagious, noroviruses
spread particularly rapidly wherever people are
in close contact.
Outbreaks often occur in settings such as schools,
hospitals, workplaces, restaurants, cruise ships,
airplanes, and other mass transportation.
Noroviruses are a group single stranded, nonenveloped RNA viruses. Human noroviruses can
be divided into three distinct genetic groups (GI,
GII, and GIV), which can be further subdivided
into at least 25 genotypes.
The genetic diversity of noroviruses is due to the
error prone nature of RNA replication, where
mutations are relatively common, drive the
evolution of new strains of norovirus, and in turn
drive new outbreaks.
While people can develop immunity to particular
strains of norovirus that they have been exposed
to, this immunity does not protect against
infection from other norovirus strains and it
diminishes over time.
There is no vaccine or drugs to prevent
or treat norovirus
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If infection occurs, drink plenty of fluids to
prevent dehydration. Hospitalization may be
necessary in cases of
severe dehydration.
Hand washing, washing food, and
regularly disinfecting surfaces helps
prevent the spread of norovirus
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Hands should be washed with soap and water for
at least 20 seconds after using the toilet;
changing diapers; or preparing, handling, or
serving food.
Fruits and vegetables should be carefully washed
and shellfish thoroughly cooked before serving.
Throw away any food suspected of being
contaminated with norovirus.
Anyone who is sick should not prepare food or
care for others and should refrain from doing so
until at least 2-3 days after they recover.
Clean and disinfect all surfaces that come into
contact with someone sick with vomiting or
diarrhea with a 5-25% chlorine bleach solution.
Clothes or linens that come into contact with
vomit or stool should immediately be washed
thoroughly.
More research is necessary to answer
key questions, develop drugs and
vaccines
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Many important research questions remain
unanswered including:
o What are the molecular markers that
signify that someone has developed
immunity to a strain of norovirus?
o How long does immunity to a particular
norovirus strain last?
o How long after a person recovers from
norovirus infection are they still able to
transmit the virus?
Although no antiviral drugs exist to treat
norovirus infection, researchers—including GVN
Board of Directors member Dr. Raymond Schinazi
and colleagues at Emory University—are
investigating compounds and approaches that
could lead to a safe and effective therapeutic.
However, no candidates have been developed far
enough to begin clinical trials in humans.
Several experimental norovirus vaccines have
entered early stage clinical trials in humans and
have shown promise at reducing the incidence
and severity of disease. However, concerns
remain about these candidates’ abilities to
confer long lasting immune protection across
multiple norovirus strains.
Work on mice noroviruses by researchers in Dr.
Christiane Wobus’ lab at the GVN Center of
Excellence at the University of Michigan
contributed to the development of a new way
to grow human noroviruses in the laboratory by
researchers in Dr. Stephanie Karst's lab at the
University of Florida. The new approach uses a
type of immune cells called b cells to grow
human norovirus and depends on the presence
of particular bacterium, Enterobacter cloacae.
This is a major discovery that could allow
researchers to study noroviruses in the lab in
ways that were previously not possible.
References:
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Jones MK, Watanabe M, Zhu S, Graves CL, Keyes LR,
Grau KR, et al. Enteric bacteria promote human and
mouse norovirus infection of B cells. Science. 2014;
346(6210), 755-759.
Ahmed SM, Hall AJ, Robinson AE, Verhoef L,
Premkumar P, Parashar UD, et al. Global
prevalence of norovirus in cases of gastroenteritis:
a systematic review and meta-analysis. The Lancet
Infectious Diseases. 2014;14(8):725-30.
MM Patel, MA Widdowson, RI Glass, K Akazawa, J
Vinjé, UD Parashar. Systematic literature review of
role of noroviruses in sporadic gastroenteritis
Emerging Infectious Diseases, 2008; 14: 1224–1231
Costantini VP, Whitaker T, Barclay L, Lee D,
McBrayer TR, Schinazi RF, and Vinjé J. Antiviral
activity of nucleoside analogues against norovirus.
Antiviral therapy. 2012; 17(6), 981.
Glass RI, Parashar UD, and Estes MK. Norovirus
gastroenteritis. New England Journal of Medicine.
2009; 361(18), 1776-1785.
Centers for Disease Control and Prevention Division
of Viral Diseases. Updated norovirus outbreak
management and disease prevention guidelines.
MMWR. 60, no. RR-3 (2011): 1.
Robinson CM, and Pfeiffer JK. Leaping the norovirus
hurdle. Science. 2014; 346(6210), 700-701.
Karst SM, Wobus CE, Goodfellow IG, Green KY, &
Virgin HW. Advances in norovirus biology. Cell host
& microbe. 2014; 15(6), 668-680.
US FDA. The Bad Bug Book (Second Edition). 2012.
Available at:
http://www.fda.gov/Food/FoodborneIllnessContam
inants/CausesOfIllnessBadBugBook
Web Resources:
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WHO World Health Day 2015 Page:
http://www.who.int/campaigns/world-healthday/2015/event/en/
WHO Food Safety Fact Sheet:
http://who.int/mediacentre/factsheets/fs399/en
US CDC Norovirus page:
http://www.cdc.gov/norovirus/index.html