Diebel: Viral Gastroenteritis

Question 1

What is the most common route of transmission for viral gastroenteritis?

Answer 1

fecal oral

Question 2

How does viral gastroenteritis cause secretory diarrhea?

Answer 2

infection and damage to the proximal bowel

Question 3

If you have viral gastroenteritis, does your stool contain leukocytes?

Answer 3

NO (usually bacterial)

Question 4

What are common sxs of gastroenteritis?

Answer 4

nausea
vomiting
abdominal pain

Question 5

What viruses tend to cause more severe vomiting?

Answer 5

noroviruses (less common for rotavirus)

Question 6

Do you treat viral gastroenteritis?

Answer 6

No, it’s self limiting, but w/out supportive care can lead to death in hard to reach areas of the world.

Question 7

What are the major causes of viral gastroenteritis?

Answer 7

rotavirus (winter, young children <5)

norovirus- norwalk virus (outbreaks of food borne illness, adults, year round)

Question 8

What are the minor causes of viral gastroenteritis?

Answer 8

adenovirus

astrovirus

Question 9

Rotavirus

Answer 9

RNA virus
icosahedral
nonenveloped (but it's double shelled!)
class III- DS, segmented
Reoviridae

REO- respiratory enteric orphan

*related to coltivirus

Question 10

What is unique about the capsid of the rotavirus?

The segmented genome of the rotavirus is significant b/c…

Answer 10

Double shelled *very stable

You can get reassortment of the genes to create new strains.

Question 11

What are the natural hosts for rotavirus?

Answer 11

humans
vertebrates

*host-range restricted

Question 12

What is the tropism for rotavirus?

Answer 12

Mature absorptive villous epithelium of the upper 1/2 of the SI.

Question 13

What happens to Rotavirus after replication in the SI? What is the virus confined to?

Answer 13

infectious particles are released into the intestinal lumen> undergo further replication in the distal areas of the small intestine.

Infection is generally confined to the intestinal mucosa

Question 14

How does Rotavirus replicate w/in the cell?

Answer 14

RNA particle brings everything it needs for trxn. As the virus particle is released from the infected cell it dies through lysis and death causes diarrhea symptoms. When the virus is immediately released, the second core needs to go through maturation in the SI, and then it will be infectious.

Question 15

What is the only example of a viral toxin protein?

Answer 15

NSP4 (enterotoxin)

Viral protein that has a cytotoxic affect in the SI. NSP4 can lodge in the lumen and disrupt Ca stores in the cells which contributes to cell death and the secretion of ions into the small intestine further exacerbating diarrhea.

Question 16

How does rotavirus attack and wreak havoc in your body?

Answer 16

1. Affects epithelial cells of SI
2. 8 hrs post infection> begin to see cytoplasmic inclusions where replication is taking place
3. At height of infection you can get 10 billion viral particles/ g of stool

Question 17

What is the global distribution of deaths from rotavirus?

Answer 17

More common in parts of the world where malnourishment is more common.

Almost every child under 5 will have a rotavirus infection, but if you have vit A def it can exacerbate the infection.

Question 18

What vaccines are used to treat rotavirus?

Answer 18

Rotarix

Rotateq

Question 19

Rotarix

Answer 19

Live attenuated

Made of human strain of virus that’s been attenuated

Question 20

Rotateq

Answer 20

Live attenuated

hybrid between human and cow strain of rotovirus. Hybridization of virus particle allows it to be attenuated

Question 21

Norwalkvirus-Norovirus

Answer 21

RNA
icosahedral
non-enveloped
IV SS+ non-segmeneted
calciviridae
calcivirus

*adults, all year around, cruise ships, accounts for 50% of all foodborne gastroenteritis

Question 22

What sxs are associated w/ norovirus?

What is a distinguishing feature of fevers in norovirus?

Answer 22

diarrhea
vomiting
abdominal cramps
nausea
HA
anorexia
Fever

no higher than 101 F

*High mutation rate and high number of strains means that immunity is short lived.

Question 23

What is GII.4 Syndney?

Answer 23

New strain of norovirus

Strain emerged in March 2012 in Australia. Has quickly become the predominate strain causing both cruise ship and land-based outbreaks worldwide.

Norovirus can mutate quickly (causing DRIFT). Results in new strains every few years.

Norovirus infections are the leading cause of gastroenteritis in the US causing about 21 million infections each year and 800 deaths

Question 24

Adenovirus (40-42)

Answer 24

DNA
icosahedral
nonenveloped
I- DS DNA linear
Adenoviridae
Mastadenovirus

*Tissue tropism for Sml Intestine (40-42)

Question 25

How do you diagnose adenovirus 40-42 in a lab?

Answer 25

Direct analysis of the clinical sample without virus isolation is possible.

Rarely used except for epidemiological purposes.

1. Immunoassays (either fluorescent antibody or ELISA)
2. PCR / DNA probe analysis

Hard to differentiate from noro and roto.

Question 26

How do you prevent adenovirus?

Answer 26

careful hand washing
chlorination of swimming pools

live oral vaccines for types 4 and 6

Question 27

How do you treat adenovirus?

Answer 27

No approved txs

supportive care

Question 28

A 10-month-old baby (roto) girl brought to ER in winter (roto). Vomiting, watery diarrhea, fever (sxs of gastroenteritis) w/ acute onset (roto and noro). Attends a day care (roto). Now WBCs in stool (viral infection).

Vitals: Fever (above 101–> ROTO), elevated RR, hypotensive

PE: dry mucous membranes, listless, febrile.

Blood: Elevated BUN and creatinine–> dehydration (worse SE from roto infection)

Most likely causative organism?

Answer 28

Possible organisms should include:
ETEC E. coli, Vibrio cholera, C. difficle, C. perfringens, Giardia, Cryptosporidium (immunocompromised), rotavirus, norovirus

High fever, above 102, in 30% of cases (rotavirus)

Question 29

How could you confirm a diagnosis of rotavirus?

Answer 29

Stool viral antigen test.

Failed investigations – electron microscope examination> double capsid.

Question 30

How should you tx rotavirus? Prevent?

Answer 30

rehydration, supportive care

vaccine available

Question 31

Within 42 hours (rapid onset) after a college basketball game in Indianapolis, 94 students (adults- noro) with symptoms of gastrointestinal disease (large group w/ sxs at same time) visited the university clinic. The predominant symptoms included nausea, vomiting (severe in some cases- NORO), diarrhea, fever, headache, and myalgias.

Vital Signs: Temp = 38.5C (101 F- above 101 is max for noro), Pulse = 98/min, Respiratory Rate = 17 breaths/min, Blood Pressure = 105/61 mmHg

Physical Exam: patient showing mild distress due to abdominal pain and nausea, abdominal exam showed mild tenderness, rectal exam revealed no blood.

Most likely causative organism?

Answer 31

Likely acute nonbacterial gastroenteritis caused by NOROvirus.

Explosive nature of cases, high rate of nausea, vomiting, and diarrhea, coupled with low incidence of fever. Enteric virus most likely in adult cases.

Question 32

What do you do next to confirm acute nonbacterial gastroenteritis?

Answer 32

Stool viral antigen test. RT-PCR.
Electron microscope examination.

No leukocytes and no blood in the stool.

Question 33

How do you treat acute nonbacterial gastroenteritis?

Answer 33

rehydration and supportive care

Question 34

How do you diagnose norovirus in the lab?

Answer 34

RT-PCR
EM
ELISA assays to viral Ags themselves or to Ab response

Question 35

What are tx for norovirus?

Answer 35

peptobismal

*combat by minimizing outbreaks (food handling safety and pure water supply)