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Foodborne & Waterborne
Disease Viruses
2. Norovirus & Rotavirus
Suphachai Nuanualsuwan
DVM, MPVM, PhD
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Noroviruses
1. Virus particle
• formerly Norwalk-like viruses since first
outbreak in Norwalk, Ohio, U.S.A.
• gastroenteritis virus
• one of 2 human Calicivirus genera
• small round, structured viruses (SRSV)
• ~ 30-38 nm
• single structural protein
• ssRNA(+) of 7,500 bases
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Suphachai
DVM, MPVM, PhD
Electronmicrographs and model of Caliciviruses
50 nm
Calicivirus
Norovirus
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Suphachai
DVM, MPVM, PhD
Noroviruses
2. Disease
• gastroenteritis
• mild and self-limiting
• “winter vomiting disease”
• projectile vomiting
• incubation period is dose-dependent
• incubation period & illness duration 24-48 hr.
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Suphachai
DVM, MPVM, PhD
Noroviruses
3. Transmission and Control
• major virus shedding in 1.vomitus and 2.stool
• infection
• primary infection : food or water
• secondary infection : infected patients
• aerosol droplet can shed virus on the fomite
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Suphachai
DVM, MPVM, PhD
6
Suphachai
DVM, MPVM, PhD
Noroviruses
4. Epidemiology
• person-to-person by fecal-oral is main route
through food handlers
• institutional outbreak : the poor sanitation
• food & water contaminated with virus particles
• shellfish e.g. oyster
• recreational water
• no age specific
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Suphachai
DVM, MPVM, PhD
Noroviruses
5. Stability
• in case of prevention broke
• need to inactivate virus in food or water
• nature of FB-WB disease viruses are resistant
to the environment
• inactivation (data usually from epidemics)
• drying on the fomite surface
• pH
• heating
• Ultraviolet(UV) and chlorine
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Suphachai
DVM, MPVM, PhD
Noroviruses
6. Food and Risk factors
A safe food handler
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Suphachai
DVM, MPVM, PhD
Shellfish
• bivalve mollusk
• found in shallow coastal, estuarine water
• feeding by filtration
• accumulate virus particles
• eating raw or undercooked shellfish?
oyster
mussel
clam
cockle
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Suphachai
DVM, MPVM, PhD
Shellfish
• thoroughly cooking to inactivate viruses
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Suphachai
DVM, MPVM, PhD
Shellfish
• Relaying and Depuration
• not standard for viruses
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Suphachai
DVM, MPVM, PhD
Personal sanitation of food handlers
A safe food handler
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Suphachai
DVM, MPVM, PhD
Noroviruses
• formerly Norwalk-like viruses
• Caliciviridae family
• incubation and illness ~ 24-48 Hr.
• gastroenteritis virus
• distinctive symptom: vomiting
• virus shedding in vomitus and stool
• transmission: fecal-oral route
• diagnosis: epidemiology, symptom, RT-PCR
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Rotavirus infection
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Suphachai
DVM, MPVM, PhD
Rotavirus
1. Virus particles
• Reoviridae family
• double coat protein & icosahedral symmetry
• diameter of 70-80 nm
• 11 dsRNAs -> re-assortment
• diverse serotypes
• Group A rotaviruses (7 serotypes)
• mostly found in children < 5 years
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Suphachai
DVM, MPVM, PhD
Rotavirus
2. Implicated food
• Shellfish
• food and water contaminated with viruses
• pre-harvest and post-harvest
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Suphachai
DVM, MPVM, PhD
Rotavirus
3. Disease
• gastroenteritis -> acute diarrhea
• vomiting, fever, and respiratory illness
• water and electrolyte loss
• malnutrition as aggravating factor
• serious in children, mild for adult
• incubation period ~ 1-3 days
• illness duration ~ 4-6 days
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Suphachai
DVM, MPVM, PhD
Rotavirus
4. Epidemiology
• shedding virus ~ 8 days after disease onset
• institutional outbreak
• very low infective dose
• children < 5 years ~ 6-24 %
• diverse serotypes -> re-infection
• short-term IgG(<2 wk) -> re-infection
• non-seasonal
• associated with sanitation
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Suphachai
DVM, MPVM, PhD
Rotavirus
5. Transmission/Control
• food & water
• fertilizer, sewage
• water treatment, supplies, distribution
• fomites and environmental surface
• relative humidity, porous surface
• sediment
• hands and fingers
• 63 % of transmission
• polyvalent vaccine
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Rotavirus
• fecal-oral route <- sanitation
• gastroenteritis, vomiting, fever
• children < 5 years got serious illness
• short-term immunity 2-4 weeks
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Suphachai
DVM, MPVM, PhD
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