Foodborne Dz: Viral Flashcards
T/F: Viruses are the most common cause of foodborne illness
TRUE
T/F: Testing for viral etiologies of diarrheal dz is routinely done
FALSE
Hepatitis __ virus accounts for about 90% of viral hepatitis infections worldwide
A
T/F: Majority of Hepatitis A infections are asymptomatic
TRUE
**infection in infancy or childhood is asymptomatic
Where does hepatitis A replicate? How is it shed?
replicates in the liver and causes hepatitis
then the virus is shed into bile and is excreted in the feces
Many cases of hepatitis A are acquired when _______
Traveling
Who is the most important reservoir of Hepatitis A?
Humans
via feces
The virus is shed 1-3 weeks before illness and up to several weeks after recovery ***long shedding period
T/F: In areas with high endemicity of Hepatitis A there are numerous clinical cases reported
FALSE
- in these areas the majority of the population are infected as children - therefore there is minimal clinical dz
- occurs in least developed countries with poor socioeconomic status
In more developed countries where there is a low endemicity of Hepatitis A, is there a high or low clinical disease?
There are more outbreaks of clinical disease
In these countries, the average age of infection goes up. More adults are susceptible
*remember in children/young people - they tend to be asymptomatic
What are the modes of transmission of Hepatitis A and which is most important?
Direct: Fecal-oral = most important (close personal contact, poor personal hygiene, infected food handlers)
Vehicle: food, water contaminated with feces (improper sewage tx)
*associated foods = shellfish from contaminated waters, raw produce, Contaminated drinking water, Uncooked foods and cooked foods that are not reheated after contact with an infected handler
What is the incubation period of hepatitis A?
average is 28 days
Can range from 15-50 days
What is the duration of illness associated with Hepatitis A?
varies from 2 weeks to 3 months
What clinical signs will be associated with a Hepatitis A infection?
fatigue, dark urine, jaundice, flu-like symptoms
Nausea/vomiting, anorexia, fever, malaise, or abdominal pain
What is described as a positive case definition of hepatitis A according to the CDC?
- discrete onset of clinical signs: nausea, anorexia, fever, malaise, or abd pain
- Jaundice or elevated serum aminotransferase
AND
Either positive serologicatl test for IgM to Hep A
OR
An epidemiological link to a lab confirmed case (within the household/sexual partner)
How can Hep A be prevented?
- Target the host: Vaccination (this will reduce the reservoir)
- Target the vehicle: proper sewage/water tx, proper preparation, cooking, and handling of food - wash veggies and fruit, ***good sanitation
- Block transmission: personal hygiene and hand washing
What is the group of related single stranded RNA, non-enveloped viruses, that cause acute gastroenteritis in humans, and are also known as “winter vomiting disease”?
Noroviruses
(family- calicivirues)
6 recognized groups
What is the most common cause of foorborne illness around the world?
noroviruses
Noroviruses account for ____% of all KNOWN foorborne illnesses in the US
58%
only 20% of all domestically acquired foodborne illness
Who is the reservoir of Noroviruses?
How is it shed?
PEOPLE
Feces** and vomit
Shedding begins 18 hours post infection - usually lasts for about 28 days (ranges from 13-56d)
**95 billion viral particles per gram of feces
T/F: Once infected with a norovirus, you will gain immunity and likely not be infected again
FALSE
*there are multiple strains with little cross protection
What are the modes of transmission of noroviruses?
- Direct: fecal oral route (close personal contact, poor personal hygiene)
- Vehicle:
a- food/water contamination with feces (Infected food handlers = MOST IMPORTANT) Also improper sewage tx
–> associated foods: shellfish harvest from contaminated waters, raw produce, uncooked or cooked foods that are not reheated after contact with infected handler
b- FOMITES: surfaces contaminated with fecal material (virus can survive at least one week on counters/surfaces)
What is the incubation period and duration of illness of noroviruses?
Incubation= 12 to 48 hours
Duration of illness = 24 - 72 hours
What clinical signs are associated with noroviruses?
Nausea, acute onset of vomiting, watery non-bloody dhr with abdominal cramping
What are the Kaplan Criteria used to determine if an outbreak was caused by a norovirus? (there are four requirements)
- Mean (median) illness duration = 12-60 hours
- Mean (median) incubation period = 24-48 hours
- More than 50% of people affected –> vomiting
- No bacterial agent found
(other diagnosis done by Real time PCR of stool/vomit/environmental samples)
Who is norovirus treatment most important for?
Children
Supportive care: fluids/electrolytes
How can norovirus be prevented?
- Target vehicle: proper preparation, cooking, handling of food (MOST IMPORTANT), good sanitation
- Block transmission: personal hygiene, and hand washing
T/F: Outbreaks of norovirus are often smaller scale
FALSE
Often larger due to: multiple potential modes of transmission, prolonged asymptomatic shedding, virus stability in environment, lack of cross protective immunity
The increase in gastroenteritis on cruise ships is primarily attributed to ______
Noroviruses
What shellfish has norovirus been known to be transmitted through?
Raw oysters
T/F: Strains of rotavirus in animals and people are distinct
TRUE
The most common cause of severe diarrhea in children around the world is ______
Rotavirus
most (95%) of children infected by 5 years of age in the US
When do seasonal outbreaks of rotavirus tend to occur?
In the winter
November to April
Who is the reservoir for rotavirus? How is it shed?
People are the reservoir
shed through feces 2-10 days after onset of dhr
T/F: Subsequent infections with rotavirus have mild or no diarrhea
True
First infection provides partial immunity
What is the mode of transmission of rotavirus?
- Direct: fecal-oral route (close contact with infected person/poor personal hygiene)
- Vehicle - food/water contaminated with feces (contaminated by infected food handlers - salad, fruit)
FOMITES: contaminated with feces - virus lasts for weeks in the environment
Where are rotavirus transmission risks the highest for children?
Day care centers
Hospitals
Parents who work in day cares or hospitals
*immunodeficient people also have high infection risk
What is the incubation period of rotatvirus? How long is the typical duration of illness?
Incubation is less than 48 hours
Duration of illness = 3-7 days
What clinical signs are associated with rotavirus infection?
Diarrhea - in most cases is self limiting
May see temporary lactose intolerance
Dehydration, electrolyte imbalances
*infections in children 3-36 months are most severe
What are the definitive case definitions for rotavirus infection?
None: just acute dhr in children under 36 months that are not vaccinated - outbreaks are usually in the winter
and
Rotavirus antigen in stool detected with enzyme immunoassay
How are rotavirus outbreaks prevented?
- target the host = vaccination
- Target the vehicle: Proper preparation, cooking, and handling of food. Good sanitation
- Block transmission: personal hygiene, hand washing, diapers etc
What is the rotavirus vaccination strategy?
Vaccinate at a very young age to delay age of infection
What are other viral agents that can cause GI signs in humans and are transmitted via contaminated food?
Astroviruses
Adenoviruses
Parvoviruses
- usually self limiting infections
- prevention via targeting vehicle (food prep sanitation) and blocking transmission (hand washing)
T/F: Foodborne viral illnesses typically have longer incubation periods than bacterial pathogens
FALSE
Typically shorter **Hep A is the exception
T/F: Foodborne viral illnesses tend to cause more vomiting and less diarrhea than bacterial foodborne illnesses
TRUE
virus = vomit
Which foodborne illnesses tend to have a longer duration of symptoms, viral or bacterial?
Bacterial have longer duration
