Transcript Norovirus Update-NHICEP March 13th, 2007

Norovirus Activity
New Hampshire, 2006-2007
Beth Daly, MPH
Communicable Disease Epidemiologist
Communicable Disease Surveillance Section
NHICEP Meeting
March 13, 2007
NH Department of Health and Human Services
Division of Public Health Services
Viral Gastroenteritis
• Several viruses cause gastroenteritis
– rotavirus, noroviruses, adenoviruses, sapoviruses, and
astroviruses
• Symptoms are often similar among etiologies,
often unable to distinguish clinically
• CDC: each year 23 million cases of acute
gastroenteritis are due to norovirus infection
• At least 50% of all foodborne outbreaks of
gastroenteritis can be attributed to noroviruses
NH Department of Health and Human Services
Division of Public Health Services
Norovirus
• Genus name of a group of of related, singlestranded RNA, nonenveloped viruses
• Member of the Caliciviridae family which includes
four viral genera:
– Lagovirus, Vesivirus, Sapovirus, Norovirus
• Only sapovirus and norovirus can infect humans
• Previously known as “Norwalk-like Viruses”
• Norwalk virus is just one type of virus in the
Norovirus genus
• Norwalk virus named for original strain which
caused an outbreak in Norwalk, Ohio in 1968
NH Department of Health and Human Services
Division of Public Health Services
Norovirus Genogroups
• There are five norovirus genogroups
(divided into at least 31 genetic clusters)
– Only 3 of these genogroups can infect humans
(GI, GII, GIV)
– Genogroup GI: Norwalk virus, Southampton
virus, Desert Shield virus
– Genogroup GII: Hawaii virus, Snow Mountain
agent, Toronto virus (GII/3)
– Genogroup GIV: Ft. Lauderdale virus
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Clinical Presentation
• Incubation period: 24-48 hours
– median in outbreaks 36 hours
• Acute-onset:
– vomiting, watery non-bloody diarrhea, abdominal
cramps, nausea
• Symptoms may vary based on genogroup
• Dehydration most common complication
• Results in reversible lesions in jejunum
– precise mechanism diarrhea and vomiting unknown
• Symptoms last 24 to 60 hours
• Recovery is complete and no evidence of serious longterm effects
• Asymptomatic in 30% of infections
– role in transmission unknown
NH Department of Health and Human Services
Division of Public Health Services
Transmission
HANDS FOOD
ES
AIR
• Humans only known reservoir
– Some noroviruses present in swine, cattle, and
mice, but these genogroups do not infect
humans
• Transmitted primarily fecal-oral
– consumption of contaminated food/water
– direct person-to-person spread
– Environmental/fomite contamination
• Good evidence exists for transmission due to
aerosolization of vomitus
– droplets contaminating surfaces or entering
oral mucosa and swallowed
• Multiple routes seen in outbreaks
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H2O
Transmission
• Highly infectious
– As few as 10 viral particles may be
sufficient for infection
• Viral shedding usually begins with onset
of symptoms
– Presymptomatic shedding may occur
• Shedding may continue for 2 weeks after
recovery
– Unclear to what extent viral shedding
72 hours after recovery signifies
continued infectivity
NH Department of Health and Human Services
Division of Public Health Services
MMWR 2001; 50: RR-9
NH Department of Health and Human Services
Division of Public Health Services
Immunity
• Immunity may be strain-specific
• lasts only a few months
• individuals are likely to be repeatedly
infected throughout their lifetimes.
• Antibodies to the virus are noted
initially in young children ages 3 to 4
• Antibody prevalence exceeds 50% by
age 50
NH Department of Health and Human Services
Division of Public Health Services
Immunity and Blood Type
• Susceptibility to infection may be
genetically determined
• People with blood group O at greatest risk
for severe infection
• Noroviruses bind to several histo-blood
group antigens and different genogroups
have differing affinity for ABO antigens
• GI noroviruses preferentially recognize blood group
antigens A and O
• GII noroviruses preferentially recognize blood group
antigens A and B
NH Department of Health and Human Services
Division of Public Health Services
Diagnosis
• RT-PCR detects norovirus RNA
– can be used to test stool and emesis samples
• NH PHL requests stool
– Identification of virus can be best made from
stool taken within 48 to 72 hours after onset
• good results can be obtained on samples
taken as long as 5 days after onset
• Virus can sometimes be found in stool
samples taken 2 weeks after recovery
NH Department of Health and Human Services
Division of Public Health Services
Epidemiology
• CDC estimates 23 million cases of
norovirus each year in US
• In NH, norovirus is not reportable
• Outbreaks are reportable
• What defines an outbreak?
– Transmission within the facility?
– Higher than normal number of cases?
NH Department of Health and Human Services
Division of Public Health Services
Reported Outbreaks of Viral
Gastroenteritis, 2002-2007
Year
Foodborne
Person-to-person
Total
2002
2
33
35
2003
1
29
30
2004
4
17
21
2005
3
16
19
2006
3
31
34
2007 YTD
0
46
46
Total
13
172
185
Note: Number of outbreaks includes all outbreaks with a
suspect or confirmed viral etiology
YTD: as of 3/1/2007
NH Department of Health and Human Services
Division of Public Health Services
Reported Outbreaks of Viral
Gastroenteritis, 2002-2007
50
45
40
35
30
25
20
15
10
5
0
2002
2003
2004
2005
2006
NH Department of Health and Human Services
Division of Public Health Services
2007 YTD
2006-2007 Norovirus Season
• Between December 1st-March 1st
– 64 outbreaks of norovirus/norovirus-like illness in
institutional settings
• 55 (86%) in longterm care facilities
• 4 (6%) in acute care hospitals
• 5 (8%) in schools
– 50 (78%) outbreaks submitted stool specimens
• 25 (39%) met CDC criteria for a confirmed norovirus
outbreak (≥ 2 positive specimens)
• 18 (28%) had one positive stool specimen
• Increase seen across the United States
• CDC believes increase due to new strain
NH Department of Health and Human Services
Division of Public Health Services
Control- Public Health
• Notify the NH DHHS Disease Control
Section immediately if you suspect an
outbreak in your facility
• Follow NH DHHS Guidelines for Control of
GI Outbreaks in Institutional Settings
• Collect stool specimens
– Be sure to label lab requisition form with the
word “OUTBREAK” and your Facility Name
– Also helpful if you could write name of NH
DHHS public health nurse you’re working with
NH Department of Health and Human Services
Division of Public Health Services
Control- Patient/Resident
• Stop all group activities
• Consider alternate ways of feeding the ill
to prevent them from dining in common
areas
• Restrict/defer admission to affected areas
for two incubation periods after last case
• Notify visitors and encourage
handwashing during/after visits
NH Department of Health and Human Services
Division of Public Health Services
Control- Staffing Issues
• Staff with GI symptoms should remain out of
work until 48 hours after symptom resolution
• Exclude non-essential staff from affected areas
• Interrupt movement of inter-department staff if
possible
• Staff should frequently wash hands using soap
and water during suspect norovirus outbreaks
• Use gloves and aprons whenever contacting an
affected individual or contaminated environment
NH Department of Health and Human Services
Division of Public Health Services
Control- Environmental
• Noroviruses 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
– can survive in up to 10 ppm chlorine well in excess of
levels routinely present in public water systems
• CDC recommends cleaning surfaces with 1000
ppm household bleach
– equivalent to 5 tablespoons per gallon
– Can other cleaners be used?
NH Department of Health and Human Services
Division of Public Health Services
What about Alcohol Based
Hand Sanitizers?
• Attacks protein envelope of the virus
• Noroviruses are non-enveloped!
Nucleic acid genome
(DNA or RNA)
Lipid-protein envelope
Protein shell
(capsid)
20-300 nanometers diameter
NH Department of Health and Human Services
Division of Public Health Services
Thank you!
Questions/Comments?
Contact NH DHHS to report suspect
outbreaks and to receive disease
control recommendations and support
Office: 271-4496
After Hours: 800-852-3345 ext. 5300
NH Department of Health and Human Services
Division of Public Health Services