What it is
How it is identified
How to control it
• Norovirus, Norwalk-like viruses and calicivirus are all
linked with patients who are diagnosed with acute
enteritis. This virus will start to show signs as early as
12 hours after exposure, but usually is seen 24-48 hours
after ingestion of the virus.
• Norovirus is a member of small round structured virus of the
• There are 27-30 nm viral particles and contain a single stranded
• The virus is genetically diverse which are further associated with
2 genotypes (GI and GII). These genotypes are identifies by
sequence analysis which is done in investigations.
• Immunity is complicated and yet not fully understood but
protection is usually short lived and strand specific.
• The inability to culture slows the process of diagnostic tests.
• Has been associated with outbreaks of gastroenteritis
among adults and with sporadic cases occurring among
children. These viruses account for 40-80 percent of
• Outbreaks have been reported in various settings
including hospitals, nursing homes, communities, cruise
ships, schools and restaurants.
• Health acquired infections may be common, however
limitations in the availability of diagnosis assays have
made determination of hospital acquired disease
• Transmission has been documented through
direct person-to-person contact, as well as
through contaminated food, water, ice, and
• Winter are most common for outbreaks but can
be year round.
• No commercial diagnosis is currently available.
• Diagnosis is usually made via electron microscopy (EM)
of stool specimens as virus is present in modest
quantities during acute infection.
• After the first 48 hours of infection the yield of EM in
detecting norovirus rapidly declines.
• Molecular diagnostics use a process of Reverse
transciptase-polymerase chain (RT-PCR)which are
more sensitive and specific. This type of diagnostic test
can provide important epidemiologic information on
genogroup clusters and identification of individual
• Serological assays can be used to detect
norovirus infection as serum IgG in acute phase
and convalescent phase samples. These are
mostly done in an outbreak investigation if
• Antigen based tests on stool samples can
simplify and speed diagnostics.
• Viruses are very different from bacteria and
parasites, some of which can cause illnesses
similar to norovirus infection.
• Viruses are much smaller and are not affected
with antibiotics or cannot grow outside of a
• Some patients will experience low grade fever,
chills, headaches, muscle aches and general sense
• The illness begins suddenly and usually includes
nausea, vomiting, diarrhea and some stomach
• The illness happens suddenly and the people
affected may feel very sick.
• Stomach flu not related to the respiratory flu or
• Viral gastroenteritis
• Non-bacterial gastroenteritis
• Food poisoning
• Norovirus is usually not serious as the virus will run it
course in 1-2 days and have no long-term health effects.
• People affected may feel very sick and have multi
episodes of the symptoms throughout the course.
• As people are unable to drink a lot of liquids to
replenish the fluids and electrolytes lost might need
• The most severe dehydration cases are seen in the very
young, the elderly and those with weakened immune
• Dehydration with hemodynamic collapse and
life threatening electrolyte imbalances are the
most severe consequences of the virus.
• Small children and the elderly are the higher risk
population for rapid dehydration.
• Elderly people with comorbidities such as renal
dysfunction or cardiac issues may reequire closer
attention to fluid status during this viral
• Norovirus is very contagious and difficult to
control once it takes hold. Anyone that is
infected with norovirus are contagious from the
moment they fall ill to at least three days after
recovery. Cases have shown that sometimes
people can be infectious for up to two weeks
• Particular care should be taken in young
children in diapers who have diarrhea.
• Norovirus is found to be transmitted via the fecal-oral
• Transmission of this virus is also from contaminated
food, water and ice.
• Touching environmental surfaces or objects
contaminated with the virus and then placing their
hands in their mouth.
• Having direct contact with another person who is
infected and showing symptoms.
• Virus is shed in stool in highest concentrations during
• Good personal hygiene and adherence to
Standard or Contact precautions should
minimize the risk of transmission.
• Restriction of employees with symptoms from
patient care and patient environments as well as
food handling should be enforced.
• Contact isolation is recommended if an outbreak
• Patients should remain in their room limiting possibility
• Staff who have symptoms should not come back to
work until 3 days after recovery of no further
• Adequate disinfection of the infected rooms should be
• Bleach solution is recommended as a disinfectant.
• Improvements in sanitation and increased use of oral
rehydration have led to significant reductions in this
• Currently there is no specific therapy available
for norovirus. It is a self-limited condition and
supportive care and fluid and electrolyte
replacement is the best treatment plan for this
• In most cases people that are at risk for
dehydration can be managed with careful
attention to fluid status and oral rehydration
avoiding the need for intravenous fluids.
Exercise: Outbreak process
• Scenario: Small inpatient hospital setting
• Day 1- patient presenting with complaints of
• 4 hours later same patient having active diarrhea
and vomiting and the roommate also reports
having diarrhea. Caregivers state stool foul
smelling. Physician orders stool cultures to rule
• 2 hours later you have 2 staff members calling in sick
for GI symptoms. 1 hour later you find out that 2
other patients are having GI symptoms.
• Recap: Started with 1 patient then within 8 hours you
have total of 4 patients and 2 staff members that are
presenting with GI symptoms.
10 hours from first case:
• Another patient starts with nausea and diarrhea
• Cultures are negative for C-Diff all patients still
• Early on in day; 3 more patients are having GI
Called State Health Department
• Informed Health Department of possible
outbreak as multi cases in last 24 hours. Health
Department states no cases being identified in
area. Health Department comes to help identify
problem. Tests for stool cultures obtained to
rule out certain bacteria and viruses.
End of day 2
• Total of 8 patients and 2 staff presenting with
• No more cases of symptomatic patients but 1 staff has
symptoms. Some of the patients and staff from Day
one are feeling better and 1 staff is back to work.
• Tracking and surveillance are well underway and
contact precautions are instituted to any patient who
has symptoms. All patients with symptoms are now in
isolated area away from compromised patients. Strict
hand hygiene is being monitored more aggressively and
• Education given to staff on possible problem
and control measures to be taken.
• Had a staff meetings to inform of infection and
opportunity to ask questions and inform of extra
precautions being taken to prevent transmission.
• Health Department confirms that Norovirus was found in two
of the cultures and no more cultures needed to be taken as virus
is now identified and steps need to be taken to contain the virus.
• As virus is now confirmed control is now in maintaining the
spreading of the virus.
• Also more patients and staff now showing symptoms. Visitors
were informed of the a gastrointestinal virus in the building and
visiting discouraged. Education given to visitors that chose to
• As virus was identified staff now restricted from returning back
to work until 3 days after symptoms are resolved.
End of week 1
• Recap: By the end of the week you have a total
of 9 patients and 13 staff that were affected by
• Less cases are being seen on patients but continue with
staff. Day 8-14 total of 9 staff and 4 patients.
• As staff were not returning to work at least 3 days after
symptoms resolved the following week showed
• 20 days from onset now have no more new cases this
week with the precautions being taken we had 2 staff
and no more patients this last week.
What to Do
• Before outbreak identified follow procedures of
your facility on infection control.
• After outbreak is identified initiate the extra
• Once source of outbreak is identified follow
recommendations to control transmission.
• Active surveillance on both staff and patients that are
• Hand hygiene well enforced
• Surveillance of compliance of precautions being taken.
• Contact isolation
• Staff compliance to not returning to work until the 3
• Most important active teamwork by all involved
whether it be staff, patients, and visitors.
• Enforce and monitor environmental disinfection.