Food and Water borne Viruses Flashcards
Where do viruses transmitted in food and water originate
Human GI tract, contaminate food/water and are transmitted via faecal oral route due to poor hygiene ect.
What are the characteristics of viruses transmitted in food and water
- no envelope (resistant to low pH, heat ect)
- can remain infectious for over a month in contaminated food and water
- highly contagious as very few virus particles needed to establish an infection (high viral load excreted)
Which 3 food and water borne viruses are responsible for the vast majority of gastroenteritis caused by viruses
Norovirus, Hepatitis A and Hepatitis E
Describe Norovirus
Non-enveloped, +ve ss RNA genome, Infects immune cells and Intestinal epithelial cells, member of caliciviridae family
What is the Norovirus structure
Naked virus, icosahedral capsid composed of VP1 capsid protein with 19 dimmers of this protein that make up capsid. VP2 is minor capsid protein which enables stability of virus. Single stranded RNA and VPg involved in translation and a poly a tail involved in stability and translation
How many different genotypes does the Norovirus have
50 different genotypes (high mutation rate)
What factors likely contribute to the increase of Norovirus cases in winter
-Post-pandemic changes in population immunity
-Changes in diagnostic testing capabilities
-Changes in reporting to national surveillance
-A true rise in norovirus transmission due to the emergence of GII.17 genotype (mutation)
Describe the Hepatitis A virus (HAV)
Non enveloped (excreted in stool); quasi-enveloped (eHAV) found in blood
+ve sense ssRNA genome
Picornaviridae family
Primarily affects hepatocytes (liver epithelial cells),
leading to inflammation.
How many genotypes does HAV have
6 genotypes ( low mutation rate)
Which HAV genotypes infect humans
Genotypes I-III
Which is the most prevalent Norovirus genotype
GII.4
Capsid made up of 4 different proteins (VP1,2,3 and 4), single stranded RNA genome, 5VPg protein linked to stability and translation and 3’poly A tail linked to stability and translation
What are the sources of viruses in food and water
- ready to eat foods handled by infected individuals
- raw or uncooked shellfish from contaminated water
- contaminated water sources
- uncooked foods e.g. fruits,vegetables and salads
- direct contact with infected individuals e.g vomit, faeces entering mouth
What are the symptoms of Norovirus
High temperature, flu- like symptoms (tiredness, headache, muscle pain), nausea, vomiting, abdominal pain, diarrhoea
What are the symptoms of HAV
High temperature, flu like symptoms, nausea, vomiting, upper abdominal pain, diarrhoea, constipation, pale yellow or grey faeces, dark brown urine, pruritis ( itchy skin), yellowing of skin and whites of eyes
What is the incubation period for HAV
14-28 days
How is is HAV diagnosed
Clinically indistinguishable from other acute viral hepatitis – HBV, HCV
Blood test
Specific diagnosis by detection of anti-HAV IgM antibodies, or HAV RNA genome by RT-PCR
How is Norovirus diagnosed
Usually diagnosed only on symptoms
Stool sample – RT-PCR or antigen detection
What is the difference between Norovirus and HAV
HAV is acute, self-limited (immune recovery by itself) gastroenteritis, with jaundice while Norovirus is acute, self-limited gastroenteritis
What is the recovery time for Norovirus
Most patients recover in 1-3 days
What is the recovery time for HAV
Most patients 3-6 months and then have lifelong immunity
What can you develop from HAV, particularly in elderly patients or patients with pre existing liver disease
Fulminant hepatitis (acute liver failure)
How do we vaccinate HAV
multiple vaccines available – most are inactivated virus vaccines, e.g. Avaxim, Havrix, Vaqta
Offered to high risk individuals, including international travellers; in USA recommended for all children ages 1-2 years.
Two doses, 6 months apart (over 1 year of age)
