Studies of Norovirus Infectivity and Persistence: Why the Food Service Industry should be Vigilant

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Studies of Norovirus Infectivity and Persistence
Why the Food Service Industry should be Vigilant

• Christine L. Moe
• Hubert Dept of Global Health
• Rollins School of Public Health

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Overview

• Background
• Norovirus human challenge studies of infectivity
• Studies of Norovirus Persistence
• Water
• Environmental Surfaces
• Human Hands
• Efficacy of various of handwash agents against
  Noroviruses

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Noroviruses

• Group of small round structured viruses 27-33
  nm diameter
• Single strand, plus-sense RNA, 7.5 kb genome with
  three open reading frames
• Classified as Caliciviridae
• Two human genera noroviruses and sapoviruses

Norwalk virus S. Miller, Duke Univ
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Norovirus Phylogenetic Tree
Kageyama et al., 2004
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Norovirus Background

• Most common cause of epidemic acute
  gastroenteritis
• Estimated 23 million cases in US annually
• Paradigm since 1972
• Can not be cultured in vitro
• Culture in 3-D rotating cell system reported by
  Straub et al., 2007
• No animal model
• Infection of gnotobiotic piglets reported
  by Cheetham et al., 2006

B.V. Prasad
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Clinical Presentation

• Acute gastroenteritis with predominant vomiting,
  nausea, abdominal cramps, diarrhea
• Incubation period 24 - 72 hours
• Duration 12 - 72 hours
• High attack rates ave 45

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Norovirus Outbreaks
Port Everglades, Florida, November 2006
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Virus sickens nearly 700 aboard cruise
ship POSTED 1252 GMT (2052 HKT), November 20,
2006 FORT LAUDERDALE, Florida (AP) -- A thorough
scrubbing of the Carnival Liberty began Sunday as
the ship docked after a virus sickened nearly 700
passengers on a trans-Atlantic cruise. Fourteen
guests and five crew remained ill and in
isolation when the ship arrived at Port
Everglades, according to a statement released by
Carnival Cruise Lines, a brand of Carnival Corp.
Some passengers were escorted off the ship in
wheelchairs by crew wearing blue
gloves. Preliminary tests identified the source
of the outbreak as the highly contagious
norovirus, which had struck several guests just
before they boarded the cruise November 3 in
Rome, Carnival officials said. More than 530
guests and 140 crew reported to the ship's
infirmary with similar symptoms during the 16-day
voyage.
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Transmission Mode and Settings of 348 Norovirus
Outbreaks USA,1996-2000
MMWR, 2001
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Norwalk-Like VirusCrosses the Scrimmage
LineTransmission During a Football Game

• KM Becker, CL Moe, KL Southwick and JN
  MacCormack. (2000) Transmission of Norwalk Virus
  During a Football Game. N Engl J Med
  343(17)1223-1227.

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Foods implicated in outbreaks of viral
gastroenteritis or hepatitis

• Salads
• Fruit salad and cut fruits
• Produce (green onions)
• Raspberries, strawberries (fresh and frozen)
• Shellfish
• Deli meats
• Sandwiches
• Cake icing

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How do foods become contaminated with Noroviruses?
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Opportunities for Food Contamination during
Growth and Harvest

• Soil
• Irrigation water
• Hands
• Equipment

Susan Lance-Parker, GA Dept of Health D Bacon,
1996. http//dbacon.igc.org/Mexico/border00.htm
http//www.roncastle.com/images/new-orleans-pictur
es/oysters.jpg
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Opportunities for Food Contamination during
Processing and Preparation

• Processing water/ice
• Hands
• Equipment/surfaces

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Unpublished data slides have been deleted
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What do we know about Noroviruses?

• Our data from human challenge studies confirm
  that noroviruses are highly infectious
• Some norovirus infections are asymptomatic
• Infected people can shed very high numbers of
  norovirus in their stool
• Viral shedding can sometimes occur for 3 weeks
  after symptoms have resolved.
• Majority of reported norovirus outbreaks are
  associated with food service settings or events
• Our data indicates that norovirus RNA can persist
  on common kitchen surfaces for at least 3-6 weeks
• Need EFFECTIVE cleaning and disinfection agents
  and protocols to remove norovirus contamination

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What do we know about Noroviruses?

• Our data show that norovirus RNA is very stable
  on human hands for at least two hours
• Our data indicate that some hand sanitizers are
  not effective at reducing norovirus RNA on hands
• Our data suggest that some new products we
  evaluated, used alone or in combination, appear
  to be very effective at reducing norovirus RNA on
  hands
• Need to continue to develop more effective
  products for reducing noroviruses on hands to
  reduce risks of foodborne and person-to-person
  transmission

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What do we know about Noroviruses?

• Our RT-PCR data indicate that Norwalk virus RNA
  is stable in groundwater for more than two
  months.
• Our human challenge study indicates that Norwalk
  virus remains infectious in water for at least 61
  days.
• Need to examine persistence of infectivity in
  water at longer time points.
• Development of norovirus vaccines is in very
  early research stages. Food service workers are
  an important target group for norovirus vaccines.