In select populations, severe gastroenteritis can lead to hospitalization. Name these populations.
-very young, elderly, immunocompromised
Acute infectious gastroenteritis (AIG) is especially a concern in which environment?
- hospitals
- especially viruses
AIG accounts for ______ of deaths among children < 5 y.o. worldwide.
- 15%
- one of the leading causes of early childhood death in resource-poor countries
Describe the common infectious causes of AIG between developed and developing countries.
- developed: mainly due to viruses
- developing: mainly due to parasites and bacteria**
For AIG, diarrhea is always a symptom. T/F.
- False; variety of signs and symptoms
- diarrhea, vomiting, fever, cramps, irritability, headache, anorexia, malaise, etc…
Differential diagnosis of AIG is broad. List some epidemiological clues that can help.
- time of year
- age of patient
- travel history
- careful exposure history
- vaccination history
Enteric pathogens are classically divided into 3 categories based on how they effect host GI physiology. Name these 3 categories.
- minimally invasive or enterotoxin-secreting causing watery diarrhea
- Inflammatory or cytotoxic destruction of mucosa of small bowel or collow leading to diarrhea with leukocytes and blood in stool
- penetrate through intact mucosa and access reticuloendothelial system leading to systemic illness (enteric fever syndrome)
Viral GE is caused by many viruses and all present with a similar disease or suddent onset and short duration (1-10 days). Describe the stools.
- water stools without mucous or blood
- fecal leukocytes absent of minimal
- often called stomach flu
Viral GE is self-limited in healthy, well-nourished persons with normal immune systems. But what 3 characteristics are seen in the immunocompromised?
- chronic diarrhea
- increased mortality
- prolonged fecal shedding
* *also serious illness in those unable to rehydrate**
List the 5 viruses covered, their families, and their genomes, if they are enveloped or not.
- Rotavirus; reoviridae; segments dsRNA
- Adenovirus; adenoviridae; linear ds DNA
- Norovirus; caliciviridae; +ssRNA
- Sapovirus; caliciviridae; +ssRNA
- Astrovirus; astroviridae; +ssRNA
*ALL NON-ENVELOPED Fecal oral is possibility!!
When does viral GE hit? What age is its peak incidence?
- 70% of admissions occur in winter
- viruses account for 50-90% of acute GE requiring hospitalization
- peak incidence in 6-24 months, but can affect all ages and classes worldwide
List the 5 viruses discusses, their peak age of incidence, and when they occur.
- Rotavirus; 6 months-2 yr. old; Winter in temperate places or year round in tropical
- Adenovirus; infants and young children; year round-epidemics
- Norovirus; children AND adults; winter peak with year round occurrence
- Sapovirus; children (infants and toddlers) mainly and adults; year round
- Astrovirus; mainly young children; year round
With the exception of ________, the incubation period is very short for most of these viruses. Vomiting and diarrhea usually lasts for several days or more, with prolonged diarrhea being observed for the ____________ vomiting and diarrhea being of very short duration for _________. Shedding of the virus in stools in affected individual last for 8-10 days for most viruses, with what exception?
- adenovirus
- adenovirus (12 days) and noro (4-6)
- norovirus
- norovirus
Transmission of viruses causing gastroenteritis
- fecal oral route from person to person
- contaminated fomites
- contaminated food or water
- possible respiratory secretions
Heathcare-associated spread is common with viral GE, particularly for which ones?
- rotavirus
- norovirus
What is viral GE transmission so efficient? What is an efficient way to kill these viruses?
- physical hardiness of GI viruses due to no envelope
- high virus concentration in stools
- highly contagious; will only 10-20 particles needed for infection
- resistant to inactivation by various standard cleaning solutions
- can be inactivated by antiseptic agents that have high concentrations (>40%) of alcohols and by bleach
Pathological changes associated with Viral GE
- usually patchy with intervening areas of apparently normal mucosa
- shortening of villi, exfoliation, elongation of crypts, increase in mononuclear cells in lamina propria
- virus multiplies in enterocytes at tips of villi
What has been the leading cause of severe dehydrating diarrhea necessitating hospitalization in infants and young children worldwide?
-rotavirus
Describe the structure of rotavirus
- family reoviridae (respiratory enteric orphan)
- naked
- triple-layered icosahedral capsid
- double stranded segmented RNA
- particles resemble wheels
Rotavirus is composed of 11 RNA segments. What do they encode?
- 6 structural proteins (VP1-VP4, VP6, VP7)
- 6 nonstructural proteins (NSP1-6) involved in genome replication
How are rotaviruses seriologically classified?
-classified into 7 serogroups (A-G) based on VP6 properties
Severe GE caused by rotavirus commonly affects what age group?
-infants and children 6 months-2 years old
Marked seasonality to rotavirus in temperate climates with what conditions promoting spread? Where will outbreaks occur?
- cool, dry weather
- readily spread in day-care centers, neonatal units, and families
Why does rotavirus not infect infants right after birth?
-infants less than 3 months old are protected by passive maternal antibody
