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Emilio DeBess DVM, MPH
Epidemiologist
Acute and Communicable Disease Prevention
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The Historical Norovirus
Caliciviruses: Norovirus & Sapovirus
Norovirus Outbreaks in Oregon Long Term
Care Facilities
Questions?
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Norovirus is a genus of genetically
diverse single-stranded RNA, non-
enveloped viruses in the Caliciviridae
family.
The known viruses in the genus are all
considered to be the variant strains of a
single species called Norwalk virus.
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The viruses are transmitted by fecally
contaminated food or water; by person-
to-person contact; and via aerosolization
of the virus and subsequent
contamination of surfaces.
Noroviruses are the most common cause
of viral gastroenteritis in humans, and
affect people of all ages.
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Norwalk, Ohio: the Outbreak
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Bronson-Norwalk Township School
Halloween 1968
In October 1968, an outbreak of acute
gastroenteritis among students and teachers in
an elementary school in Norwalk, Ohio was
investigated by the Centers for Disease Control
and Prevention.
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During a two-day period, 50% of the students
and teachers (116 of 232) developed a
gastrointestinal illness with a secondary attack
rate of 32% among contacts of primary cases.
Vomiting in 90% of cases and diarrhea in 38%
of affected individuals, and the duration of
illness was typically 12 to 24 h.
Lab tests did not reveal an etiological agent.
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1969-1972:
The Laboratory of Infectious Diseases (LID) at
the National Institutes of Health (NIH) embarks
on an intense search for a non-bacterial (viral)
etiological agent of acute gastroenteritis.
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June 1972:
The 27-nm virus-like particle is
discovered by the use of immune
electron microscopy, from an infectious
stool filtrate derived from an outbreak of
gastroenteritis in an elementary school in
Norwalk, Ohio. It is described as a “small
round-structured virus” (SRSV).
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1975: CDC creates the Vessel Sanitation Program
(VSP) to minimize the risk for gastrointestinal disease among passengers and crew aboard ships by assisting the cruise ship industry in developing and implementing comprehensive environmental health programs.
Today, the VSP is an important organization in the surveillance and prevention of norovirus outbreaks.
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October 1977:
Sapporo virus is first detected during a
gastroenteritis outbreak in a home for
infants in Sapporo, Japan. It is
distinguished by its typical surface
morphology.
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1990:
The norovirus genome is finally cloned
and sequenced, allowing its classification
in the Caliciviridae family.
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1992:
Sapoviruses are officially identified as
genetically distinct from noroviruses. This is
accomplished through the cloning and initial
genetic characterization of a genome of human
calicivirus with “classical” morphology and
comparison with the cloned genome of
Sapporo/82/Japan.
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1995-1996:
“95/96-US” strain of ‘Norwalk-like viruses”
cause 60 outbreaks in geographically distant
locations within the US and are identified in an
additional 7 countries on 5 continents during
the same period.
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November 2003:
Spanish authorities close the border with the
British colony of Gibraltar before the arrival of
a virus-stricken cruise ship carrying some
2,000 passengers. More than 400 passengers
on the ship fell ill with a norovirus after the ship
left Southampton, England, for a Mediterranean
voyage on Oct. 20.
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Virus has been known since 1968
Picturesque names
Small round structured virus
Winter vomiting disease
Norwalk virus
Epidemiology has changed dramatically since 2002
Wrecks havoc in long term care facilities
non-enveloped SS-RNA viruses
Vesivirus
Group 1
Norwalk
Desert Shield
more
Caliciviruses
Lagovirus Sapovirus Norovirus
Group 2
Farmington Hills
Hunter
Minerva
New Orleans
Sydney**
Other Group 1
Houston
Manchester
more
Group 2
Cruise Ship
London
Bristol
more
Group 3
poultry Group 4
Osaka
Angelholm
more
Why are we suddenly having so many gastro
outbreaks?
Norovirus strain replacement
GII.4 Sydney
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waterborne outbreaks: Arizona, Lawson et al., 1988
foodborne outbreaks: Louisiana, Kohn et al., 1995
military outbreaks: Iraq, Bailey et al., 2005
maritime outbreaks
naval: Persian Gulf, Sharpe et al., 1995
cruise ships: United States, Widdowson et al., 2004
long term care facility outbreaks
Oregon, 2003-2012
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Characteristics of caliciviruses:
Very low infectious dose
Stable in the environment
High percentage of “vomitters” leads to
widespread environmental contamination
Easy transmission from person-to-person
Caliciviruses: Norovirus & Sapovirus
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Classic profile of signs and symptoms
Signs (residents and staff, 03-12)
Diarrhea 86%
Vomiting 72%
Fever 16%
Symptoms (staff only, 2003 data only)
Cramps 67%
Nausea 78%
Myalgia 42%
Fatigue 80%
pathognomonic
Ohio
Oregon
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Norovirus a chronic problem in nursing homes, long-
term care facilities in Oregon.
Acute gastroenteritis (AGE): acute-onset vomiting, diarrhea, or both
without another apparent cause.
AGE outbreaks in LTCFs and hospitals:
• General definition: an "unusual" number of patients, residents or
employees with AGE clustered by time and place
• Working definition: two or more patients, residents or employees in
the same LTCF or on the same hospital unit with AGE onset dates
within 96 hours of each other (two incubation periods of most
gastroenteritis agents) of each other
• Lab-confirmed AGE outbreak: 2+ stool samples that test positive for
the same pathogen
• "Unexplained" AGE outbreak: 4+ stool samples that test negative for
any pathogen (all unexplained AGE outbreaks will now be tested for
sapovirus, a Calicivirus similar to norovirus)
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Farmington Hills
strain emerges
2002
Sakai &
Minerva
strains emerge
2006
Sydney
strain emerges
2012
New Orleans
strain emerges
2009
0
20
40
60
80
100
120
140
160
180
200
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013
All noro outbreaks
LTCF noro outbreaks
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0
10
20
30
40
50
60
70
80
90
100
August, 2012 September,2012
October, 2012 November,2012
December,2012
January, 2013 February,2013
March, 2013 April, 2013 May, 2013
long term care retirement school restaurant/deli other
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0
5
10
15
20
25
30
August,2012
September,2012
October,2012
November,2012
December,2012
January,2013
February,2013
March,2013
April,2013
May, 2013
GI GII.6 GII.4 New Orleans GII.4 Sydney other GII
Long term care facilities Organizational chart w/ numbers & percentages of residents
Department of Human Services
Office of Licensing & Regulatory Oversight
Community-based
Care (CBC)
Nursing Facilities
(NF)
Assisted Living
Facilities (ALF)
Residential Care
Facilities (RCF)
14,275 (40%)
36,081 residents
9,601 (26%)
12,205 (34%)
Long term care facilities Organizational chart w/ numbers & percentages of residents &
outbreaks*
Department of Human Services
Office of Licensing & Regulatory Oversight
Community-based
Care (CBC)
Nursing Facilities
(NF)
Assisted Living
Facilities (ALF)
Residential Care
Facilities (RCF)
14,275 (40%)
36,081 residents
9,601 (26%)
12,205 (34%)
917 outbreaks*
*2000-2013 (YTD)
338 (37%)
365 (39%) 202 (22%)
Norovirus cases, norovirus incidence rates,
October 13, 2011 thru May 20, 2013
DATA & STATS DETAILS
Cases (numerator): collected by LTCFs on the Gastroenteritis Case Log;
entered in Case Log Database
Case definition: resident or staff w/ vomiting, diarrhea or both from
10-13-2011 thru 05-20-2013; lab-confirmed, epi-linked to lab-confirmed case,
or case in a norovirus-like outbreak
Population (denominator): number of beds as a proxy for the number of
residents adjusted for partial years
Caveat lector: incidence rates are underestimated (too low)
Case counts incomplete
Occupancy of beds < 100%
“Oregon Norovirus Watch”: Norovirus cases organizational chart w/ numbers &
percentages of facilities & outbreaks
Lab-confirmed and presumptive (epi-linked) norovirus cases
October 13, 2011 thru May 20, 2013
Residents Staff Total Cases
Frequency Rate per 100
residents Frequency
Assisted Living Facilities 1831 7% 593 2227
Residential Care Facilities 1268 5% 682 1174
Nursing Facilities 870 6% 304 1950
Total 3772 7% 1579 5351
Comparison
Campylobacteriosis (Oregon, 2011): 25.6/100,000 or .025% of Oregonians
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Up-to-date info about Calicivirus outbreaks in Oregon https://public.health.oregon.gov/DiseasesConditions/
DiseasesAZ/Pages/disease.aspx?did=110 Investigative guidelines for local health
https://public.health.oregon.gov/DISEASESCONDITIONS/COMMUNICABLEDISEASE/OUTBREAKS/Pages/gastro.aspx
CDC norovirus page http://www.cdc.gov/norovirus/index.html
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Emilio DeBess –DVM, MPH Epidemiologist 971-673-11111 , emilio.e.debess@state.or.us Local Health Department Contact information at: http://www.oregon.gov/DHS/ph/lhd/lhd.shtml
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