by Jennifer P. Collins, M.D., FAAP, and
Larry K. Pickering, M.D., FIDSA, FPIDS, FAAP
• Shah MP, Wikswo ME, Barclay L, et al.
“Near Real-Time Surveillance of U.S. Norovirus Outbreaks by the Norovirus Sentinel Testing and Tracking Network – United
States, August 2009–July 2015.” MMWR
Morb Mortal Wkly Rep. 2017;66:185-
Noroviruses are the predominant cause of
foodborne illness in the United States. Since
Food and Drug Administration licensure of
the two currently available rotavirus vaccines
in the U.S. in 2006 and 2008, noroviruses
have become the leading cause of pediatric
Noroviruses are genetically diverse and are
classified into at least six known genogroups
and are further subdivided into at least 38
genetic clusters (genotypes). Worldwide,
genogroup II genotype 4 has been the predominant virus for the past decade. However, new variant
strains emerge within this genotype every two to four
years and frequently are associated with increased
Norovirus gastroenteritis is characterized by sudden onset of nausea, vomiting, watery diarrhea and
abdominal cramps that develop following a 12- to 48-hour
incubation period. Systemic
symptoms such as fever, malaise,
myalgia and headache also may
occur. Symptoms typically last 24
to 60 hours, but longer courses
can occur in young children and the elderly in whom
dehydration can be a major problem.
Reverse-transcriptase polymerase chain reaction
or enzyme immunoassay testing of stool specimens
can confirm the diagnosis. Treatment of norovirus
gastroenteritis is supportive, including oral or intravenous hydration.
Noroviruses are environmentally stable and can
be transmitted from person-to-person, through
consumption of contaminated food or water and
through contact with contaminated environmental
surfaces. Several factors promote spread of noroviruses, including a low infectious dose, large numbers
of viral particles in stool and vomitus, and prolonged
viral shedding. Additionally, asymptomatic excretion
is common in all age groups,
especially young children.
Hand hygiene is the most
important method for preventing transmission of noroviruses. Washing hands with
soap and water has been shown
to be more e;ective than use of
Since 2009, the Centers for Disease Control and
Prevention (CDC) has performed an enhanced na-
tionwide surveillance of norovirus outbreaks.
;e CDC began obtaining epidemiologic data on
norovirus outbreaks through the National Outbreak
Reporting System (NORS) and CaliciNet in 2009.
NORS is a web-based platform for health departments to report waterborne, foodborne and enteric
disease outbreaks of all etiologies, including norovirus. CaliciNet is a nationwide electronic surveillance
system of local and state public health and regulatory
agency laboratories that collects genetic sequences
of norovirus strains associated with gastroenteritis
In 2012, the NoroSTAT surveillance system was
implemented in five states (Minnesota, Ohio, Oregon, Tennessee and Wisconsin). NoroSTAT was designed to integrate the NORS and CaliciNet systems
and thereby reduce reporting lags and incomplete
reporting of norovirus cases. ;e referenced MMWR
article reports data collected
between the three-year periods before and after introduction of the NoroSTAT
NoroSTAT was associated
with a significant decrease in
reporting time — from a median of 21 days to three days
— resulting in near real-time
monitoring of outbreaks in
these five states. NoroSTAT
states also demonstrated a
significant increase in linkage of outbreak data between
the NORS and CaliciNet
systems from 86% to 95%.
More modest improvements
were seen in non-NoroSTAT
states, which was attributed
to improvements in the reporting interface and increased engagement among
reporting agencies. Nationwide, the most common
mode of transmission was person-to-person, and
outbreaks occurred most frequently in long-term
As of August 2016, NoroSTAT was expanded to
include nine states (Massachusetts, Michigan, South
Carolina and Virginia were added to the initial five
sentinel sites). Data collected are representative of
national trends, which can help inform public health
response. ;e NoroSTAT network has demonstrated
a key advancement in norovirus outbreak surveillance by providing near real-time monitoring of norovirus outbreak activity and emerging new strains.
Dr. Collins is a post-residency training fellow in
pediatric infectious diseases at Emory University
School of Medicine. Dr.
Pickering was editor of
the AAP Red Book from
2000-’ 12. He is adjunct professor of pediatrics at Em-
ory University School of Medicine.
More information on noroviruses can
be found in the AAP Red Book, https://
MMWR in Review
Norovirus surveillance system provides near real-time tracking of cases
Which of the following statements are true?
A. The NoroSTAT network has reduced the median interval for reporting of norovirus outbreak data from
21 days to three days.
B. Norovirus is the most common cause of pediatric viral
gastroenteritis in the United States.
C. The most frequent norovirus transmission mode is
D. States in the NoroSTAT network had more complete
reports that better linked epidemiologic and laboratory data.
E. All of the above
Ans w er: E
Courtesy of the Centers for Disease Control and Prevention
The morphology of norovirus virions is demonstrated in this digitally colorized transmission electron microscope image.
Dr. Collins Dr. Pickering
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