Viral gastroenteritis

Question 1

are all viruses obligate intracellular parasites

Answer 1

yes

• reproduce in living cells only
• no independent metabolism

Question 2

do viruses replicate via binary fision?

Answer 2

no, progeny are created in an assembly line fashion

Question 3

central goal of virtually all viruses

Answer 3

rapidly replicate new virions at the expense of the host cell

Question 4

Lytic interactions

Answer 4

are those that cause the death and lysis of the host cell

Question 5

Stages of Lytic Viral Replication

Answer 5

1. Attachment Specific receptors arrayed at cell surface - determines host and tissue specificity (trophism) and mode of spread in host
2. Penetration/entry
3. Uncoating
4. Synthesis of virion components
5. Maturation/Release

Question 6

when virus is added to a host, there is one step sudden upsurge that different than other organisms. describe it

Answer 6

• latent period: relative virus count is 0
• assembly and release: viral count increases sharply

Question 7

what are non lytic host interactions

Answer 7

• viruses may produce long-term associations with host cells that are not lethal to the host.
• The virus remains associated with the host cell, but the virus genes are largely unexpressed
• association is stable and long-term, but may be terminated under environmental conditions.

Question 8

Persistent infections

Answer 8

• Infection without cell death; unusual virus-host interaction in which the virus is found in a long-term association with the host.

Question 9

what are the three subclasses of persistent infections

Answer 9

• latent infection
• chronic infection
• transforming infection

Question 10

what are Latent Infections; give an example

Answer 10

• intermittent acute episodes of virus production between which there is an almost complete absence of virus particles and very limited viral macromolecular synthesis
• Herpes simplex, Varicella-zoster

Question 11

what are chronic infections. Give an example

Answer 11

• nonlytic production of virus, continued presence of high numbers of virus particles during periods in which clinical disease is absent
• Hepatitis B virus

Question 12

what are transforming infections. Give an example

Answer 12

• infected cells are immortalized and properties altered (transformed) to those of cancer cells.
• human papilloma virus

Question 13

gastroenteritis

Answer 13

• inflammation of stomach and intestine
• one of the most common diseases of humans
• frequent cause of mortality in children in developing nations

Question 14

gastroenteritis symptoms

Answer 14

• acute watery diarrhea is main feature of viral disease
• nausea, vomiting, cramps, malaise, anorexia, myalgia, headache

Question 15

in gastroenteritis, viral replication occurs where

Answer 15

Viral replication occurs in small intestine epithelial cells

Question 16

gastroenteritis

• length of incubation period
• length of disease

Answer 16

• 15-48 hrs incubation period
• Disease duration is typically short (3-5 days)
• Virus may be shed at low levels for days to weeks after illness

Question 17

tests for diagnose viral infections

Answer 17

Virus protein antigen detection

• enzyme immunoassay (rotazyme)
• latex agglutination screen test
• Assays are best described as generally insensitive

Question 18

treatment of gastroenteritis

Answer 18

• Primary therapy is oral re-hydration
  
  • Solutions of electrolytes plus sugar
  • ***There is no role for antibiotics in uncomplicated viral disease

Question 19

etiology of infant diarrhea (gastroenteritis)

Answer 19

Rotavirus and enteric adenoviruses

• The most frequent cause of infantile gastroenteritis is rotavirus, the most frequent US strain is G1
• First two years of life
• Disease transmission even in locations in which clean water and food are available

Question 20

etiology of gastroenteritis caused by outbreaks (fecally-contaminated food)

Answer 20

the Noroviruses - Norwalk, SRSV

• seen commonly in raw shellfish

Question 21

prevention strategies for rotavirus

Answer 21

• vaccines are now available for dominant rotavirus strains G1-G4, G9
  
  • Rotateq
    
    • 3 doses beginning at 6-12 weeks with a 4-10 week interval between doses
  • Rotarix
    
    • 2 doses

Question 22

Rotavirus: pathophysiology and course of illness

Answer 22

• Infection of small intestine villi enterocytes, disrupt osmotic function
• 5-7 day course of fever, vomiting, diarrhea

Question 23

which bacteria causes “winter vomiting disease”

Answer 23

Rotavirus causes predictable, annual epidemics during each winter season leading to the name ‘winter vomiting disease.’

Question 24

structure of enteric adenovirus

Answer 24

Double stranded DNA virus

Question 25

length of sickness caused by enteric adenovirus

Answer 25

• endemic diarrhea in infants
• Extended period: 5-12 days of diarrhea, fever, and vomiting

Question 26

length of illness caused by the caliciviruses (now referred to as Norovirus)

Answer 26

24-48 hours

• typically mild and self-limited

Question 27

caliciviruses (now referred to as Norovirus) primarily infects what age group

Answer 27

older children and adults

Question 28

caliciviruses (now referred to as Norovirus) is associated with what

Answer 28

associated with food (shellfish)

Question 29

distinguishing feature of caliciviruses (now referred to as Norovirus)

Answer 29

extraordinarily resistant to inactivation

Question 30

name the caliciviruses

Answer 30

Norwalk and SRSV’s (SRSV = small round shaped viruses) - now grouped under Norovirus