Viral gastroenteritis Flashcards Preview

Infectious Disease Unit 1 > Viral gastroenteritis > Flashcards

Flashcards in Viral gastroenteritis Deck (26)
Loading flashcards...
1

Signs and symptoms of viral gastroenteritis

Acute onset watery diarrhea (no mucus or blood) +/- vomiting

Short incubation period

Short duration

Highly transmissible

2

Acute gastroenteritis in the US compared to world

US:
2nd only to common cold in frequency
1-2 episodes/year

Worldwide:
6-7 episodes/year
Lots of deaths

3

Pathophysiology of viral gastroenteritis

Local infection of intestinal epithelial cells

Malabsorption due to virus killing mature enterocytes

Local villus ischemia leading to diarrhea

Viral enterotoxin changing the transepithelial fluid balance

4

How do diagnose viral gastroenteritis

Usually clinical

PCR (mutiplex Stool real time PCR)

5

Treatment for viral gastroenteritis

Oral rehydration

6

Prevention of viral gastroenteritis

Hygiene: handwashing, food preparation

Sanitation: toilets, water supply, diaper changing

Environmental cleaning

Isolation of patients

Vaccines: rotavirus available, norovirus in development

7

Caliciviruses: Phylogeny

Sapovirus (humans)
Norovirus

Many human serotypes:
GII.4 Sydney: first detected 2012 in Australia
Principal cause of outbreaks in US

Variants arise by mutation or recombination

8

Norovirus structure

Small round ssRNA virus, 27nm in diameter, with cup shaped indentations

Naked, non-enveloped

Viral-encoded protease cleaves viral polyproteins:

Difficult to grow in culture

9

Symptoms of norovirus

1/3 asymptomatic but shedding virus
Vomiting, watery diarrhea, nausea, cramping
Malaise, headache, myalgia, low-grade fever
Occasionally dehydration

10

Spread of norovirus

Person-to-person (fecal-oral spread)
Contaminated surfaces
Foodborne (esp shellfish)
Waterborne

Shedding after symptoms resolve

11

Incubation and duration of norovirus infection

FAST!

Incubation: 15 hrs to 2 days
Duration of symptoms: 1-2 days

12

Epidemiology of norovirus

"Cruiseship virus"

Has replaced rotavirus as #1 in areas where rotavirus vaccine in use

Most common cause of diarrheal outbreaks in older children and adults

13

Rotavirus

Huge problem in developing world

Vaccine avaialble

14

Rotavirus structure

11 double stranded RNA genome segments

Each segment encodes one viral protein (VP)

Non-enveloped, but three protein shells

Outer capsid layer: acid stability
Composed of VP7 with VP4 spikes: induce neutralizing antibody

Inner capsid layer
Contains VP6: major rotavirus group antigen

Innermost core: VP2

15

Reassortment

Reassortment allows introduction of segments from animal
rotavirus into human rotavirus, causing epidemics

16

Rotavirus Pathogenesis

Affects small intestine

Replicates in villus epithelial cells

Mononuclear inflammation

Villus shortening, stunting

Mechanism causing diarrhea is unclear
? Decreased absorptive properties of denuded villi
? NSP4 enterotoxin

High viral titers shed in stool (>10¹¹ viral particles/mL)

17

Rotavirus Enterotoxin: NSP4

Maybe neurotoxin?
Causes diarrhea in animal studies

18

Clinical manifestations of rotavirus

Up to 50% infections are asymptomatic

Symptomatic infection: abrupt onset fever and vomiting, followed by diarrhea

Stools are explosive, watery, nonbloody

Frequently leads to dehydration in children

19

Incubation and Duration of rotavirus

Symptoms last 4-8 days, self-limited

Incubation period: 1-3 days

Peak viral shedding on day 3, can be prolonged (> 3 weeks)

20

Rotavirus: Burden of Disease and epidemiology

Rotavirus is the single most important cause of severe infantile gastroenteritis worldwide

Before rotavirus vaccines in US:
Up to 180,000 hospitalization/yr
20-40 deaths/yr
In developing countries:
500,000 deaths/yr

Common disease of infants and young children

21

Treatment and prevention of rotavirus

Treatable by oral/IV rehdration

Preventable by available rotavirus vaccines

22

Spread of rotavirus

Fecal-oral
Remain infective for long periods on surfaces
Water, food, respiratory transmission less frequent

SEASONAL

23

Rotavirus: Current Vaccines

RotaTeq (RV5): Pentavalent live bovine rotavirus vaccine
Contains outer capsid proteins of 5 human RV strains made by reassortment with bovine RV genome segments
75% protective against disease, 98% protective against severe disease

Oral, 3 doses (2, 4, 6 months)
Rotarix (RV1): Monovalent live human rotavirus vaccine
Provides cross-protection against other strains
85% protective against severe disease
Oral, 2 doses (2, 4 months)

Interesting that the monovalent still offers good protection

US: # children hospitalized for rotavirus reduced by ~85%

24

What are the adenovirus serotypes that can cause gastroenteritis

40 and 41
In immunocompromised pts we think about it

25

Duration of adenovirus

5-12 days

26

Astroviruses

Small non-enveloped single stranded RNA virus, star-shaped capsomers

Trypsin necessary to activate infectivity

2-8% of diarrheal ds in children

Excreted for prolonged periods in immunocompromised

Person-to-person and foodborne spread

Outbreaks in daycares, nursing homes, school cafeterias, nursing homes