Block 3 MICRO Exam -- Positive Strand RNA viruses (#6)
Terms
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- Viruses with subgenomic RNA
-
Alphaviruses (toga)
Coronaviruses - What is different about subgenomic RNA?
- Allows production of viral proteins at DISSIMILAR levels
- Sylvatic cycle
-
"Jungle" cycle
Can include monkeys - Urban cycle is due to what
-
High density living
Humans can participate in transmission cycle significantly - How do flaviviruses enter cells?
- Endocytosis
- What do flaviviruses bud through?
- Cell envelope
- What flavivirus is NOT an arbovirus?
- Hepatitis C
- Diseases caused by flaviviruses
-
Yellow Fever
Dengue
St Louis Encephalitis
Japanese B Encephalitis
West Nile Encephalitis
Hepatitis C
Other Encephalitides - Why is yellow fever an atypical flavivirus?
- NOT an encephalitis
- Type of vaccine for yellow fever
- Live attenuated
- Symptoms of yellow fever
-
Acute febrile illness
Jaundice, hemorrhage, proteinuria - How does yellow fever spread within body?
- Hematogenously
- Where does initial growth of yellow fever occur?
- Draining lymph node nearest bite
- How is yellow fever transmitted?
- Mosquito bites
- Where is yellow fever endemic?
-
Central America
South America
Africa - Signs of Dengue Fever (DF)
-
Pain for 5-6 days
High, BIPHASIC fever - Dengue Hemorrhagic Fever
-
DF with:
Hepatomegaly
Hemorrhage
Shock
10% mortality (due to Ab to other type) - Where is Dengue fever widespread?
-
India, SE Asia, China
Japan, South America, Africa
Middle East -
Which is more severe?
Jap B or St. Louis encephalitis - Japanese B
- How many serotypes of Dengue are there?
- 4 serotypes
- How long is incubation period for Hep C?
- 8 - 10 weeks
- What is the rate of chronic infection in Hep C?
- 80%
- How is Hep C transmitted?
-
Parenterally
Infected blood, mother-child, sexually - Togavirus that is NOT an arbovirus
- Rubella (rubivirus)
- What are "spikes" on togaviruses made of?
- Surface glycoproteins E1 and E2
-
Which is larger?
Togaviruses, or Flaviviruses - Togaviruses
- Structural genes are at what end of the togavirus RNA?
-
3' end
This is reverse of picorna, flavi, etc.
Requires SUBGENOMIC EXPRESSION - How are togaviruses taken up by cells?
- Endocytosis
- What do togaviruses bud through?
- Host cell plasma membrane
- Only alphavirus that is NOT cytolytic
-
Rubella
(Exhibits limited CPE) - Rubella key points
-
Acute febrile illness w/ rash and lymphadenopathy
Respiratory transmission
Incubation ("prodrome") of 2-3 weeks
Ab appears at time of rash (lifelong immunity)
Live attenuated vaccine - Common manifestations of Congenital Rubella Syndrome
-
Congenital Heart Disease
Blindness/Cataracts
Enlarged liver/spleen
Retardation - Diagnostic sign for CRS
- Rubella virus-specific IgM in infant
- Timing breakdown for CRS pathogenesis
-
50% of abnormalities, infected during 1st month
20% during 2nd month
4% during third month
SO, timing is very important w/ regards to abnormalities developing - What virus family entails the encephalitides (WEE, VEE, EEE)?
- Togaviridae
- EEE/WEE/VEE
-
Range from mild flu-like illness to encephalitis/coma/death
Neurologic sequelae in 30%
Fatality in 35%
WEE and EEE are maintined in wild birds
Killed vaccines available - Chikungunya
-
Febrile illness found in Asia & Africa
Caused by togaviridae
Vector is same as YF and Dengue - What is the largest RNA virus genome?
- That of Coronaviruses
- Coronavirus membrane contains what three proteins?
-
E1, E2
Hemagglutinin - Where do coronaviruses bud into?
- Golgi
- How are coronaviruses released from cells?
- Exocytosis
- What are the two group names of coronaviruses?
-
229E
OC43 - Most likely source of coronavirus transmission
-
Respiratory droplets
BUT, blood and fecal/oral has been shown - Receptors for 229E coronaviruses
- Aminopeptidase N
- Receptors for OC43 coronaviruses
- Sialic Acid
- What types of cells in particular do coronaviruses destruct?
- Ciliated epithelial cells
- Characteristic shared between coronaviruses and rhinoviruses
- Poor growth in cell culture
- Seasonality of coronavirus colds
-
Winter months
Highest incidence when rhinovirus colds are lowest - Abs to coronavirus are directed against what?
- E2
- What are the incubation and symptom periods of coronavirus colds?
-
Incubation -- 2-3 days
Symptoms -- 5-7 days - Animal reservoir for SARS
- Palm civet
- Where does coronavirus replication occur?
- All throughout the body
- Incubation period for SARS
- 5 - 15 days
- Diagnostic criteria for SARS
-
Mild -- Asymptomatic
Moderate -- >100.4 F w/ cough, or SOB, or hypoxia
Severe -- above symptoms PLUS radiographic evidence - Current treatment for SARS
-
Mostly supportive
Correct hypoxia
Treat for community acquired pneumonia - Virus family of Norwalk virus (from Clin Corr)
- Caliciviridae
- Characteristic of coronas in common with NEG. strand viruses?
- Genome is coated with N protein