Micro Enteric Viruses 1

Question 1

rotavirus virology

Answer 1

double layered naked icosahedral capsid, segmented RNA genome (allows for reassortment) double stranded; environmentally rugged

Question 2

rotavirus pathogenesis

Answer 2

fecal-oral, mostly peds (contaminated toys). attach, replicate in cell, epithelial cells die and fluids exit body as self limiting diarrhea with risk of dehydration

Question 3

how does rotavirus attach to epithelial cell lining?

Answer 3

VP4 spikes

Question 4

what does rotavirus primarily infect? what does this cause?

Answer 4

cells of the small intestinal villi - impaired villus function leads to impaired hydrolysis of carbs (malabsorption)

Question 5

what causes the profuse watery diarrhea associated with rotavirus?

Answer 5

rotavirus nonstructural protein 4 (NSP4) that acts like an enterotoxin interfering with sodium transport pumps

Question 6

who does rotavirus infect?

Answer 6

children 4-24 months. adults have a few days of nausea, anorexia, and cramping pain - newborn infants seem more resistant

Question 7

exam for rotavirus

Answer 7

history of exposure; bloodless diarrhea young children with vomiting, anorexia, low fever, cramps, dehydration

Question 8

rotavirus treatment

Answer 8

most cases - no treatment. oral rehydration (pedialyte and rice-lyte)

• RotaTeq and Rotarix vaccines help reduce severity
• NO antiemetic or antidiarrheal

Question 9

norovirus virology

Answer 9

+ ssRNA, naked icosahedral capside, environmentall rugged, extremely contagious, low ID

Question 10

norovirus clinical disease - symptoms and patients

Answer 10

gastroenteritis - older age cohort than rotavirus, fecal-oral (contaminated food), more vomiting

Question 11

norovirus pathogenesis

Answer 11

• infection damages microvilli in small intesting (malabsorption)
• vomiting caused by change in gastric motility and delayed gastric emptying
• typically lasts 24-48 hr

Question 12

what are the implications of a short course with norovirus?

Answer 12

less dehydration (that combined with the older population of patients as compared to rotavirus)

Question 13

norovirus exam

Answer 13

profuse, non bloody vomiting; nausea, cramps, headache, low fever (mostly stay in gut), muscle aches, chance of dehydration

Question 14

norovirus treatment

Answer 14

rest, rehydration, antidiarrheas in adults

Question 15

what are the picornaviruses that cause enteric disease?

Answer 15

poliovirus, coxsackievirus, hepA

Question 16

picornavirus virology

Answer 16

+ ssRNA genome; environmentally rugged

-includes both rhinoviruses (resp) and enteroviruses (polio, coxsackie, hepA)

Question 17

biphasic infection

Answer 17

PICORNAVIRUS ENTEROVIRUSES
primary replication in gut with viremia and spread to regional lymph nodes leading to febrile illness and occasional CNS involvement
-may have DUAL TROPISMS replicating in both epithelium and lymphoid cells

Question 18

what are the two poliovirus vaccines?

Answer 18

inactivated: must be injected, used in first world where already irradicated
attenuated: weakened, taken orally, used in eradication effeorts

Question 19

poliovirus pathogenesis

Answer 19

fecal-oral enteric infection using CD155 receptor to enter - infects epithelial/lymphoid cells in gut

Question 20

CD155 and polio

Answer 20

how polio enters cells - present on both epithelial/lymph cells in gut AND on gray matter CNS cells

Question 21

where does polio MC infect the CNS?

Answer 21

anterior horn motor neurons of spinal cord (muscle symptoms) and brain stem (respiratory symptoms)

Question 22

signs of CNS involvement with polio

Answer 22

flaccid asymmetric weakness and muscle atrophy due to loss of motor neurons and denervation of associated skeletal muscle

Question 23

risk factors for CNS progression with polio

Answer 23

young age, advanced age, recent hard exercise, tonsillectomy, pregnancy, immunosuppression

Question 24

poliovirus diagnosis on exam:

Answer 24

nonparalytic poliomyelitis or -preparalytic: generalized nonthrobbing headache, fever, sore throat, anorexia, n/v, muscle aches - symptoms subside in 1-2 weeks
-progression to CNS involvement: headache and fever, irritability, restlessness, apprehensiveness, emotional instability, stiffness of neck and back

Question 25

polio diagnosis: tests

Answer 25

lumbar puncture: fluid pressure increased, pleocytosis, elevated protein, virus culture
MRI: anterior horn inflammation

Question 26

polio treatment

Answer 26

no specific treatment exisits - supportive care

• positive pressure ventilation for those with respiratory failure
• physical therapy

Question 27

postpolio syndrome

Answer 27

• new history of decreased muscle strength, weakness, and atrophy
• decades after polio
• fatigue, muscle and joint pain, cold intolerance
• NOT infectious: increasing dysfunction of surviving neurons

Question 28

similarities between picornaviruses, noroviruses, and rotaviruses

Answer 28

small, naked, icosahedral RNA viruses; widespread worldwide, environmentally rugged, fecal-ral transmission

• all can cause self-limited GI illness, usually resolves with no med intervention - dehydration MC complication
• pediatric - younger the worse (coxsackie B 10% lethal)