Viruses causing GE Flashcards
what is the worldwide mortality from GE?
4-10 million p/a
what is the 2nd most common cause of child death globally?
GE
what is viral GE?
inflammation of the lining of the stomach, small and large intestine
what causes complications in GE?
dehydration: fluid intake needs to be higher than that lost through vomiting and diarrhoea
how contagious is GE? how common?
Highly contagious and extremely common
what is necessary for a virus to be cause GE?
- the gut has to be both the portal of entry and the target tissue
(ie must replicate in gut and induce symptoms in gut)
how is GE spread?
oral-faecal route
- enter via food–> food poisoning
- excreted in faeces (poor hygiene, sanitation, clean water availability)
why are GE causing conditions poorly characterised?
- don’t grow well/ at all in tissue culture
do GE viruses infect at low or high doses?
low (10-100vp)
are GE viruses detectable in food?
rarely, only in Bivalbia shellfish
why is routine food screening is not feasible?
most food contamination is identified RETROSPECTIVELY
how are GE viruses detected/diagnosed?
1) electron microscopy
2) genomic tests (RT-PCR)
3) immunological tests (antigenic detection, ELISA)
what method CANNOT be used to detect viral GE causing viruses?
CELL CULTURE
what are the problems with the methods of detecting GE viruses?
- don’t tell us about infectivity
- lead to underestimation of GE infection
how can GE be prevented?
follow HACCP guidelines for food handling and safety management
what are the general features of Rotavirus?
spokes radiate from the central hub
which of the GE causing viruses are the largest?
what do their genomes have in common?
Rotavirus and Adenovirus
- both have double stranded genetic info (Adeno has DNA, Rota has RNA)
which of the GE causing viruses are the smallest? what do their genomes have in common?
Caliciviruses and Astroviruses
- both are positive sense RNA
what are the general features of Adenoviruses?
- icosahedral
- may have long fibres extending from the apices
what are the general features of Caliciviruses?
32 ‘cup-like’ indentations on the surface
what are the general features of Astroviruses?
arrangements of capsomeres gives the appearance of 5/6 pointed STAR on surface
describe Astroviruses? which group of baltimore transmission route what does it infect what does it cause
- non enveloped
- 30nm icosahedral virus
- 5-6 pointed star like appearance
- group 4 Baltimore
- worldwide distribution
- transmitted through oral-faecal route
- infects epithelial cells of intestinal tract
- cuases diarrhoea
who does Astrovirus mostly affect?
how is it diagnosed?
- young children and elderly & instituionalised patients
- diagnosed using EM, ELISA, NAAT
describe Rotavirus which family genome what type of virus what does it infect
- members of Reoviridae
- non-enveloped, 70nm icosahedral w/ spikes from central hub
- double stranded RNA divided into 11 segments, codes for 12 proteins( 1 in each segment and 2 in segment 11)
- genome protected by 3 protein shells
- hit and run virus
- infects TIPS OF MICROVILLI in intestine
what is the major cause of viral GE in infants & young children?
Rota
- 1 million deaths pa
how does Rotavirus have high transmission?
- high stability to inactivation
- quick infection (2-4 days)
- high prod of viral particles in stools
what is the target of Rota?
children
what is the treatment for Rota?
children: fluid therapy
adults: rehydration
why is Rota a hit and run virus?
poor immunity that does not protect against future infections
how are neonates protected from Rota?
Maternal passive immunity can protect for few months
are vaccines available for Rota?
now live attenuated vaccines approved for use in the US: routine vaccination with 3 doses at ages of 2, 4 and 6 months
what is the single major cause of non bacterial GE?
Noro
why is Noro so common?
v. high transmissibility
(guidelines state that those working with food (or nurseries) should not return to work for 48h after symptoms disappear)
can Noro reinfect?
yes, there is no lasting immunity
Noro is part of which family?
which genera infect humans?
Caliciviridae (consists of Vesivirus, Lagovirus, Sapovirus and Norovirus)
- Sapovirus and Norovirus infect humans causing winter vomiting disease
describe the genome of Noro? which Baltimore group
- non enveloped
- positive sense RNA genome
- Baltimore group 4
what is the function of VPg protein in Noro?
works as primer, so protein can be made from the genome
in Noro, what is the role of the SUBGENOMIC RNA?
produce only structural proteins
how quickly do symptoms appear for Noro? how long do they last?
- appear 12-48 hrs after infection
- lasts 2-3 days
how is Noro transmitted?
Transmitted via oral-faecal route:
- consumption of contaminated food
- person/fomite-to-person contact- airborne droplets (vomit)
what are the symptoms of Noro?
nausea, vomiting, diarrhoea, abdominal cramps and pain
how do the drugs used for Noro work?
Drugs against protein synthesis, protease and polymerase
is there a vaccine for Noro?
difficult because there are many serotypes and antigenic drift
VLPs (virus like particles) are under development
describe the genome of Adenovirus?
Baltimore group
- non enveloped
- icosahedral
- double stranded DNA
- Baltimore group 1
how is Adeno diagnosed?
electron microscopy
other than GE, what can Adeno cause?
- resp and eye inf
serotypes 40&41 specialise in infecting cells in the intestine
how does Adeno replicate
- enter cell
- deliver its DNA into nucleus
- make structural and non structural proteins
LONG PROCESS (~2 days)
what is defining about Adeno?
unlike the others, it is transmitted not by FOODBORNE, but by WATERBORNE
who does Adeno mostly affect?
children <2 years
what symptoms does Adeno cause?
WATERY diarrhoea
