enteric viruses Flashcards
Most common viral agent of severe diarrhea in infants and young children worldwide?
rotavirus
Info on rotaviruses
- non-enveloped particles - segmented, ds RNA genome - high antigenic diversity with lots of G and P serotypes BUT only 4-G-P combos cause most of the disease in humans!
Rotavirus/reovirus replication?
1) taken up by endocytosis and delivered to late endosomes or lysosomes where capsid proteins are proteolytically processed –> infectious sub viral particles.
**processing of capsid proteins can occur outside cell (when passing through gut) or after endocytosis in the late endosomes or lysosomes
2) **after penetration, enzymes in the core start making mRNA. **
\*\* assymetric transcription 3) some capped mRNA are assembled into assortment complexes. capped + strand serve as template for synthesizing complementary - strand
4) Assembly of virus particles occur in cytoplasm in cytoplasmic viroplasms
5) progeny released via lysis of host cell
Major cause of foodborne EPIDEMIC acute gastroenteritis in older children and adults?
- Norovirus/caliciviridae
Info on norovirus
- nonenveloped, nonsegmented, + strand RNA virus
Norovirus/caliciviridae replication?
not yet determined but similar to picornovirus replication cycle.
How are rota and noroviruses transmitted?
via fecal-oral route aka contamination
- they are also both extremely stable in the environment
Which virus is often linked to a single source? aka contaminated food (raw or steamed shellfish, cake frosting, salads) or contaminated water (cruise ship outbreaks)?
norovirus
how do rota- and norovirus infections usually present?
These viruses in patients present with nausea, vomiting, diarrhea, fever, and dehydration
Pathophysiology of rota- and norovirus
- they both initially infect villous epithelium of small intestine.
- virus replication and cell lysis cause LOSS OF CELLS IN LINING the SMALL AND LARGE intestine.
- Loss of cells cause FUNCTIONAL ALTERATION in SI villous epi cells
- glucose coupled Na transport IS IMPAIRED, BUT AC and cAMP are NOT stimulated like in cholera.
Epidemiology of rotavirus?
- before 2007 lots of rotavirus diarrhea per year in US but very few deaths in US d/t to othis bc of availability of effective fluid and electrolyte replacement.
- worldwide though many children/infants die from rotavirus diarrhea each year. ~600k
what is the difference between how antibody to rotavirus is obtained vs antibody to norovirus?
- antibody to rotavirus is obtained early in life
- ab to norovirus is acquired gradually in childhood and increase steadily over person’s lifetime!
vaccines for rotavirus?
1) rotateq- pentavelnt bovine-human reassortment virus (serotypes g1-g4 and p8)
*rotateq is life, attenuated vax given oral at 2, 4, & 6 mo of age
2) rotarix- human derived monovalent (G1, p8) live attenuated vax
*rotarix is admin orally in 2 doses started @ 6 weeks of age
vaccines for norovirus?
- no approved vax available yet
most important preventitive measures for norovirus is?
1) careful handwash
2) effective disinfection of contaminated surfaces
3) proper food prep
Info on astroviruses
nonenveloped, icosahedral, single stranded, + sense RNA virus
**characteristic star like appearance on EM
What is the second most common cause of childhood diarrhea?
second to rotavirus is the astrovirus
How is astrovirus transmitted?
-oral fecal route
what is the vax for astrovirus?
no vax available yet
describe astrovirus illness
- self limiting illness with short duration with a peak in winter months
info on enteroviruses/picornoviridae
small, isosahedral, nonenveloped, + sense RNA virus
*picorna- small rna
name 4 enteroviruses
poliovirus, coxsackievirus (group a and b), echovirus, and enterovirus
**echovirus followed by coxsackievirus group a has the most number of serotypes
clinical manifestation of poliovirus?
flaccid paralysis (poliomyelitis)
clinical manifestation of coxsakieviruses?
various illnesses such as hand food mouth disease, menangiocephhalitis, diarrhea, muscle pain, inflammation of myocardium and pericarium
clinical manifestation of echoviruses and other enteroviruses?
mild gastroenteritis
**echo = enteric, cytopathic, human, orphan
what is another enterovirus-like picornavirus?
hep A!
how do you differentiate rhinoviruses from enteroviruses?
1) acid stabilty and
2) replication @ 37 degrees Celsius
Transmission of enterovirus?
fecal-oral route
enterovirus reservoir
humans are the only known reservoir
vax for enterovirus
no vax except for polio
Incubation time of enteroviruses?
short (7-14 days)
**initially enteroviruses replicate in lymphoid tissue of the URT and the gut so these are often isolated and cultred for diagnoses via throat swab
clinical manifestation of enteroviruses?
asymptomatic infection is common
- can have malaise, fever, sore throat, headache, stiff neck
**viremia results in infection of target organs like spinal cord and brain, meninges, myocardium, and skin
info on adenovirus/picornaviridae
large, nonenveloped, linear ds DNA virus
what serotypes of adenovirus are associated with gastroenteritis?
- serotypes 40 and 41
how is adenovirus transmitted?
via fecally contaminated water.
* foodborne transmission has not yet been documented
epidemiology of adenovirus?
- generally seen in young children and infants like rotavirus and astrovirus
**most ppl have antibodies vs enteric adenovirus by the age of 3
