T4 - Gastrointestinal Virus

What are the two main groups of viruses classified as gastrointestinal infection viruses?

Picornaviridae and gastroenteritis viruses

Which viral family includes the RNA viruses Rotavirus, Norovirus, and Astrovirus?

Gastroenteritis viruses

What is the only DNA virus commonly classified as a gastroenteritis virus?

Adenovirus

Which virus is the single most important cause of severe diarrheal illness requiring hospitalization in infants globally?

Rotavirus

To which viral family does Rotavirus belong?

Reoviridae

What is the typical incubation period for Rotavirus infection?

1 to 3 days

Which species of Rotavirus is the most common cause of infections in humans?

Group A

What type of genome does Rotavirus possess?

11 segments of double-stranded RNA

Where in the host cell does Rotavirus replication occur?

Cytoplasm

What is the structure of the Rotavirus capsid?

100-nm icosahedral with a triple-layered protein capsid

Which Rotavirus protein forms the spikes extending from the outer shell?

VP4

Which Rotavirus protein forms the outer layer of the triple-layered capsid?

VP7

Which Rotavirus protein forms the intermediate layer of the triple-layered capsid?

VP6

Which Rotavirus protein forms the inner core layer of the triple-layered capsid?

VP2

Which ion is required to maintain the integrity of the Rotavirus outer capsid?

Calcium

Which Rotavirus proteins function as the RNA-dependent RNA polymerase?

VP1 and VP3

What mechanism allows different strains of Rotavirus to undergo antigenic shift?

Genetic reassortment

During Rotavirus replication, where do the transiently enveloped virus particles form?

Endoplasmic reticulum

Which Rotavirus non-structural protein acts as a viral enterotoxin?

NSP4

Which specific cells are targeted and infected by Rotavirus in the gastrointestinal tract?

Mature absorptive villous epithelium of the upper small intestine

Which viral enterotoxin induces secretory diarrhea by evoking intestinal chloride secretion?

NSP4

How does Rotavirus infection lead to the symptom of vomiting?

NSP4 induces serotonin release which stimulates the enteric nervous system

Through which two mechanisms does Rotavirus induce diarrhea?

Secretory diarrhea and osmotic diarrhea

What is the typical clinical duration of vomiting and watery diarrhea caused by Rotavirus?

3 to 8 days

A 1-year-old presents with vomiting, watery diarrhea, and sunken eyes with no tears; which virus is the most likely cause?

Rotavirus

During which season do epidemic peaks of Rotavirus typically occur in temperate climates?

Cooler months (winter)

Which age group is most frequently affected by Rotavirus infections?

Infants and young children 6 months to 2 years of age

What is the cornerstone of treatment for Rotavirus gastroenteritis?

Supportive fluid and electrolyte replacement

What type of vaccine is used to prevent Rotavirus infection in infants?

Oral live attenuated vaccine

Which molecular technique is commonly used for genotyping Rotavirus nucleic acid from stool specimens?

Real-time RT-PCR

To which viral family does Norovirus belong?

Caliciviridae

To which viral family does Sapovirus belong?

Caliciviridae

What are the two primary typing methods used in the Norovirus classification system?

VP1 genotyping and RdRp P-typing

Which Norovirus genogroup is responsible for the majority of viral gastroenteritis outbreaks worldwide?

Genogroup II (GII)

What is the characteristic electron microscopic appearance of Caliciviruses?

Icosahedral with cup-like depressions on the capsid surface

What type of genome do Caliciviruses possess?

Single-stranded, positive-sense, nonsegmented RNA

What protein is uniquely linked to the viral genome of Caliciviruses instead of a 5' cap?

VPg protein

How are the structural and nonstructural polypeptides of Caliciviruses produced during translation?

Cleaved from a precursor polyprotein

Where does replication of Caliciviruses occur within the host cell?

Cytoplasm

Which Norovirus protein acts as an NTPase and targets host mitochondrial membranes?

NS3 protein

To which host cell surface antigens does the Norovirus VP1 protein attach during infection?

Histo-blood group antigens (HBGA)

How does Norovirus infection lead to the symptom of vomiting?

By causing delayed gastric emptying (gastroparesis)

What is the typical incubation period for Norovirus gastroenteritis?

12 to 48 hours

How long does it typically take for a person to recover from Norovirus illness?

1 to 3 days

Why are antibiotics ineffective in treating Norovirus illness?

Norovirus is a viral pathogen

Which gastroenteritis virus is frequently associated with outbreaks on recreational cruise ships and airplanes?

Norovirus

Which group of patients is particularly at risk for prolonged Norovirus infection?

Immunocompromised patients

What are the two main sources of transmission for Norovirus in the global community?

Foodborne and waterborne transmission

What is the most common method used for rapid stool screening of Norovirus antigen at the point-of-care?

Rapid immunochromatographic assays

To which viral family do the astroviruses that infect humans belong?

Astroviridae

To which genus do the astroviruses that infect humans belong?

Mammastrovirus

What type of genome does Astrovirus have?

Positive-sense single-stranded RNA

How many open-reading frames does the Astrovirus genome contain?

Three open-reading frames

What is the characteristic electron microscopic appearance of Astrovirus?

Icosahedral symmetry with a star-like form

What is the primary cellular tropism for human Astrovirus?

Enterocytes

How does human Astrovirus evade the host's adaptive immune response?

By inhibiting host complement factors

Which host cell process is required for the maturation of human Astrovirus particles?

Host cell apoptosis and caspase activation

What is the typical duration of diarrhea caused by human Astrovirus infection?

2 to 3 days

A 3-year-old child presents with mild watery diarrhea lasting 2 days without bloody stools; which star-shaped virus is a likely cause?

Astrovirus

What percentage of patients with human Astrovirus infection experience severe dehydration?

0 to 5%

Which human Astrovirus serotype is the most prevalent cause of diarrhea in children?

Serotype 1

What is the main source of transmission for human Astrovirus infection?

Contaminated food and water

Does Astrovirus gastroenteritis typically require specific antiviral therapy?

No, it is generally a mild, self-limiting illness

What is the structural composition of the Adenovirus virion?

Naked icosahedral capsid with a fiber projecting from each vertex

What type of genome does Adenovirus possess?

Linear double-stranded DNA

Where does Adenovirus replication occur within the host cell?

Nucleus

Which viral structures determine the tissue tropism and serotype of Adenovirus?

Penton base and fiber protein

How does Adenovirus promote its own DNA synthesis without relying entirely on host enzymes?

It encodes its own viral DNA polymerase

Which group of human Adenoviruses is etiologically associated with infantile gastroenteritis?

Group F

Which two human Adenovirus serotypes are the most common causes of viral gastroenteritis?

Serotypes 40 and 41

In which specific tissues do Group C Adenoviruses persist as latent infections for years?

Adenoids and tonsils

Which host cell receptors are utilized by Adenovirus for attachment?

CAR receptor and integrin

Which early viral gene product of Adenovirus modulates the cell cycle to transition the host cell into the S phase?

E1A

Which Adenovirus proteins are responsible for downregulating host TNF receptors to evade immune detection?

E3 RID alpha and beta

Which Adenovirus protein modulates apoptosis by acting as a viral BCL2 homolog?

E1B 19k

Why are enteric adenoviruses difficult to identify via standard viral culture?

They are very difficult to cultivate in vitro

Which viral agent is the second most important cause of endemic diarrheal illness in infants and young children worldwide?

Enteric adenovirus

How long does viral gastroenteritis caused by Adenovirus typically last?

5 to 12 days

Which virus family includes the genera Enterovirus, Hepatovirus, and Parechovirus?

Picornaviridae

Which three major virus types are classified under the Enterovirus genus?

Polioviruses, Coxsackieviruses, and Echoviruses

How do human Enteroviruses differ from Rhinoviruses regarding pH stability?

Enteroviruses are stable at acidic pH, while Rhinoviruses are labile

What is the optimal growth temperature for human Enteroviruses?

37 degrees Celsius

What are the two common sites of isolation for human Enteroviruses from humans?

Nose/throat and lower intestine

Which host cell receptors are used for the uptake of Enterovirus 71 and Coxsackievirus A16?

SCARB2 and PSGL1

What is the initial translation product of the Picornavirus positive-sense RNA genome?

A single polyprotein

Which viral proteins make up the encapsidation structure of Picornaviruses?

VP1, VP3, and VP0

Which subgroup of Enteroviruses is the primary cause of Herpangina and Hand-foot-and-mouth disease?

Coxsackievirus A

A 4-year-old presents with fever and vesicular ulcers confined to the posterior oral cavity; what is the most likely diagnosis?

Herpangina

Which clinical feature distinguishes Hand-foot-and-mouth disease from Herpangina?

The presence of a papulovesicular rash on palms and soles

Which Enterovirus subgroup is a well-known cause of Epidemic myalgia and viral Myocarditis?

Coxsackievirus B

Which Enterovirus is strongly associated with acute hemorrhagic conjunctivitis?

Enterovirus 70

Which Enterovirus is associated with Hand-foot-and-mouth disease complicated by severe meningitis, encephalitis, and paralysis?

Enterovirus 71

By which route does Enterovirus 71 typically enter the human body?

Fecal-oral route

Where does the initial viral replication of Enterovirus 71 occur before causing viremia?

Tonsillar crypts or Peyer's patches

Which severe complication of Enterovirus 71 infection results from damage to the medulla oblongata and autonomic nervous system dysregulation?

Cardiopulmonary failure

What triggers the large release of catecholamines leading to cardiopulmonary failure in severe EV71 infection?

A cytokine storm and brainstem encephalitis

What are the sequential phases of severe Enterovirus 71 pathogenesis?

Viral response phase, CNS involvement, ANS dysregulation, Cardiopulmonary failure

A 3-year-old with HFMD suddenly develops myoclonic jerks, ataxia, and limb weakness; which phase of EV71 illness does this represent?

CNS involvement

Which cell lines are traditionally used for the laboratory isolation of Enteroviruses?

RD and Vero cells

During which seasons do Coxsackievirus infections typically peak?

Summer and early fall