Rotavirus, Norovirus, and Enteroviruses Flashcards
Rotavirus is the single most important etiologic agent of severe diarrheal illness in what age group, worldwide?
Infants and young children
Rotavirus is a Reoviridae, what does Reo mean?
Resipiratory, enteric, orphan
Describe the structure of Rotavirus.
Non-enveloped (2-3 concentric icosahedral capsids), segmented, dsRNA genome with high antigenic diversity
Describe the antigenic diversity of rotavirus and why it is important.
It is divided into 11G (VP7) and 12P (VP4) serotypes; However only 4 G-P combinations cause about 90% of disease in humans = the reason we can have a vaccine!
The rotavirus is taken in by endocytosis and delivered to late endosomes or lysosomes, what happens here?
Capsid proteins are proteolytically processed –> generates infectious sub viral particle (this can occur outside cells or following endocytosis in late endosomes/lysosomes
After rotavirus penetrates, what happens?
Enzymes within the core begin synthesizing mRNA’s; transcription is asymmetric so only individual + strands mRNAs are made
After + strands of mRNA are made what happens?
Some of the capped mRNAs are assembled into assortment complexes, the capped + strands also serve as templates for synthesis of the complementary - strands –> produces dsRNA
Assembly of the rotavirus occurs where?
Within the cytoplasm; released by lysis of the cell
Noroviruses (Calciviridae) cause what?
Major cause of food borne epidemic acute gastroenteritis in older children and adults
What is the replication scheme for Noroviruses hypothesized to be similar to? What is their structure?
Picornavirus; Nonenveloped, non segmented, + strand RNA
True or False: Rotavirus causes diarrhea primarily in the elderly and is responsible for 35-50% of diarrheal hospitalization during the last two years of life.
False; in the young and first two years of life
True or False: Norovirus are responsible for 50% of community-based outbreaks of nonbacterial gastroenteritis in school aged children and adults.
True - known as “winter vomiting disease”
How are rotavirus and norovirus transmitted?
Fecal-Oral route
Why are rota and noro stable in the environment?
No envelopes!
Norovirus outbreaks are often linked to what?
A single source; contaminated food or water (think raw or steamed shellfish, cake frosting, and salads or cruise ship outbreaks)
What do the clinical symptoms for rota and noro consist of?
N/V, diarrhea, fever, dehydration
What do both rota and noro initially infect? How do they differ from V. Cholera?
Initially infect villous epithelium of SI which leads to functional alteration in the SI. Glucose-coupled sodium transept is impaired but adenylate cyclase and cAMP are NOT stimulated
Why are deaths from rota and noro so rare in the US?
Availability of effective fluid and electrolyte replacements
What is most important for protection of reinfection by rota and noro?
Local (intestinal) immunity
Describe how antibodies to rota and noro are formed.
Ab to rota are obtained relatively early in life; ab to noro are acquired gradually and increase steadily over a person’s lifetime
Why is there a vaccine for rota and not for noro?
There are only 4 major serotypes of rota that cause the disease which makes a disease practical even in the face of antigenic shift and drift; noro immunity is not long lasting and diversity is generated via antigenic drift like other ssRNA viruses
What is Rotateq?
A pentavalent bovine-human reassortant virus covering G1-G4 and P8 (live attenuated and orally in 3 doses at 2, 4, 6 mo.)
What is Rotarix?
Human derived monovalent (G1, P8) live attenuated vaccine (given orally in 2 doses starting at 6 weeks)
How do you prevent norovirus?
Careful hand washing, effective disinfection of contaminated surfaces, proper food prep
What are the general characteristics of Enteroviruses?
Small, non enveloped, + strand RNA
What does Picorna mean and what should it help you remember?
pica + RNA (Small RNA); picor = polio, insensitive to ether (non enveloped), coxsackie, orphan virus, rhinovirus
What does poliovirus cause?
flaccid paralysis
What does Coxsackie cause?
various illnesses including meningoencephalitis, diarrhea, muscle pain, inflammation of myocardium and pericardium
What do echoviruses and other viruses cause?
Mild gastroenteritis (echo = enteric cytopathic human orphan)
What is hepatitis A?
An enterovirus-like picornavirus
How are enteroviruses distinguished from rhinovirus?
Acid stable and replicate at 37 C
How are enteroviruses spread?
Fecal oral route
Where to enteroviruses replicate?
Incubate for 7-14 days and replicate in lymphoid tissue of the URT and gut
Is asymptomatic infection common with enteroviruses?
Yes
What is meningitis caused by? What are the symptoms of it?
Poliovirus, coxsackie, and echo; fever, malaise, headache, nausea, and abdominal pain –> 1-2 days later w/ meningeal irritation and vomiting.
What is pleurodynia (epidemic myalgia) caused by? What are the symptoms?
group B coxsackie; abrupt fever and chest/abdominal pain; chest pain can be on either side or substernal and is spasmodic; lasts 2 days to 2 weeks, self limiting
What is hand, foot, and mouth disease caused by? symptoms?
Coxsackie A16; universal symptom is enanthema (ulcers in the mouth) followed by lesions on hand and feet
What is myocarditis associated with?
Group b Coxsackie
What are eye diseases associated with?
Coxsackie and echo
Can enteroviruses cause GI and skin disease?
Yes, a lot of them do
Is there a vaccine for enteroviruses?
Besides polio there are no vaccines; large number of serotypes and many are asymptomatic so it is impractical for all of them
