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9.19 Acute RNA Viruses
by Dr. Amedee at 8am
146
Microbiology
Professional
09/20/2011

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Term
What enzyme must a negative RNA virus have?
Definition
virion transcriptase
Term
Name the naked RNA viruses.
Definition
picornaviridae, caliciviridae, astroviridae, reoviridae
Term
T/F Astrovirus contains ds RNA.
Definition
false, ss rna
Term
What are the only two examples of diseases in humans caused by reoviruses?
Definition
colorado tick fever and rotavirus
Term
Enteroviruses, hepatoviruses, and rhinoviruses are all types of ____ viruses.
Definition
picornaviruses
Term
Name the different types of enteroviruses.
Definition
poliovirus (3), coxsackie A (1-22 & 24), coxsackie B (1-6), echovirus (1-9, 11-27, 29-34), parechovirus (1-4), kobuvirus (aichi prototype), enterovirus (68-71)
Term
Name the picornovirus that is also a hepatovirus.
Definition
hepatitis a
Term
How many different types of rhinoviruses are there?
Definition
1-100+
Term
Describe picornavirus virions.
Definition
small icosahedral, naked virions with + ss RNA. Capsid formed from 60 copies of nonglycosylated proteins
Term
How long does it take for one cycle of replication of a picornavirus?
Definition
6-7 hours
Term
How do picornaviruses leave the host cell?
Definition
cell lysis
Term
How do picornaviruses enter the host cell?
Definition
attachment then entry via receptor-mediated endocytosis. Receptors are members of the immunoglobulin superfamily
Term
What receptor does polio use?
Definition
PVR/CD155
Term
Of the picornaviruses, most rhinoviruses and several coxsackie viruses use which receptor?
Definition
ICAM-1
Term
Describe the translation of picornoviruses.
Definition
proteins translated at one polyprotein and initated at internal ribosome entry site. Polyprotein cleaved by a viral protease. Viral RNA synthesis through "-" strand intermediate with VPg at 5' end. Terminal cleavage of VPO into VP2 and 4 matures particle
Term
Describe the poliovirus polyprotein.
Definition
first capsid (P1) then noncapsid genes (p2 and 3)
Term
Describe the characteristics of enteroviruses and Hep A relevant to transmission.
Definition
resistant to pH between 3-9, detergents, heat, mild sewage tx
Term
Describe the characteristics of a rhinovirus (picornovirus) relevant to transmission.
Definition
labile at acidic pH; optimum gorwth at 33 degrees C
Term
About how many symptomatic infections do enteroviruses cause each year?
Definition
10-15 million
Term
How do enteroviruses get from where they entered the body to where they cause the disease?
Definition
intestines-> lymhphoid -> target tissue
Term
There have been no cases of wild poliovirus in the US since ___.
Definition
1979
Term
IPV (instead of OPV) has been used in the US since ____.
Definition
1999
Term
What is bulbar paralysis caused by paralytic polio?
Definition
when CNs and respiratory center in teh medulla are affected leading to paralysis of neck and respiratory muscles
Term
What are the symptoms of a mild case of polio?
Definition
mild fever with diarrhea
Term
T/F Most polio infections are asymptomatic.
Definition
true
Term
In what percent of patients is poliovirus replication limited to the GI tract?
Definition
90%
Term
T/F Polio can cause an aseptic meningitis.
Definition
true, occurs in about 2% of patients
Term
What parts of the CNS are infected by polio?
Definition
anterior horn cells of the spinal cord and motor cortex of the brain
Term
Nuerons can continue to recover from polio infections for how long?
Definition
up to 6 months
Term
What are the target tissues of coxsackie A?
Definition
herpangina and hand, foot and mouth disease, aseptic meningitis
Term
What are the target tissues of coxsackie B?
Definition
myocardial and pericardial infections, pleurodynia, and aseptic meningitis
Term
What are the target tissues of parechovirus?
Definition
respiratory and GI, rare encephalitis and myocarditis
Term
What is the target tissue of kobuvirus?
Definition
gastrointestinal
Term
What is the target tissue of echovirus?
Definition
aseptic meningitis, usually during the summer
Term
Which enterovirus infect the meninges?
Definition
echo, polio and cox
Term
Which enteroviruses infect muscle?
Definition
echo and cox a and b
Term
Which enteroviruses go on to infect the skin and cause hand, foot, and mouth disease as well as rash herpangina?
Definition
echo and cox a
Term
How do you diagnose and treat enteroviruses?
Definition
RT-PCR or viral isolation and culture. However, viremia may be undetectable at time of symptoms. CSF specimens during acute phase are positive in 10-85% of samples
treatment is supportive care
Term
What is the principle agent of the common cold?
Definition
rhinovirus (restricted to upper respiratory tract, causes mild URI in all age groups)
Term
What is the time course of rhinoviruses?
Definition
1-2 day incubation period; acute symptoms last 3-7 days
Term
How do you treat rhinovirus infection?
Definition
no specific tx or vaccine (possible block of receptor attachment)
Term
What type of virus is a norovirus?
Definition
calcivirus
Term
What are the characteristics of gastroenteritis caused by calciviruses?
Definition
family/community-wide
Term
WHat are the characteristics of gastroenteritis caused by astrovirus?
Definition
mild, self-limiting, in children
Term
What two factors contribute to a high transmission risk in viruses that cause gastroenteritis?
Definition
large quantities of virus in the stool and the virus is resistant to the environment
Term
Describe the calcivirus virion.
Definition
naked, icosahedral, positive ssRNA. Contain a single large capsid protein. Viral surface has 32 cup-shaped depressions (calici)
Term
What are the caliciviruses are medical importance?
Definition
norwalk and "norwalk like" viruses (NLV)
"sapporo-like" viruses (SLV)
Term
What is the primary agent responsible for most acute diarrheal diseasein adults and children?
Definition
norovirus (90% of all viral diarrheal disease)
Term
T/F Norovirus is considered ubiquitous.
Definition
true, 70% of people have had it by age 7
Term
What are the different genogroups of norovirus?
Definition
GI-V, which are each divided into at least 31 genetic clusters
Term
Which is the most dominant type of norovirus over the last several years?
Definition
GII.4
Term
How many particles of norovirus are needed to cause infection?
Definition
10
Term
Name the norwalk and norwalk like viruses.
Definition
norwalk, hawaii, snow mountain, montgomery county, taunton (england)
Term
What is the time frame of norovirus?
Definition
incubation period of 24-48 hours. abrupt onset with watery diarrhea, N/V, lasting 24-60 hours
Term
T/F Most norovirus infections are asymptomatic.
Definition
false, around 30% of norovirus infections are asymptomatic
Term
What percent of diarrheal cases in infants does astrovirus account for?
Definition
2-8%
Term
T/F Astrovirus cannot be grown in cell culture.
Definition
true
Term
Astrovirus particles are resistant to...
Definition
acid stable and heat resistant
Term
Describe Reovirus genome and virion.
Definition
ds RNA, segmented genome, icosahedral capsid, naked
Term
What is the leading cause of severe acute gastroenteritis among children worldwide?
Definition
rotavirus
Term
Describe the viral nucleocapsid of rotavirus?
Definition
composed of three concentric shells that enclose 11 segments of ds RNA
Term
How many serotypes are there of rotavirus?
Definition
5. the outermost layer contains two structural proteins: VP4 (protease cleaved protein, P protein) and glycloprotein (G protein) which dfined the serotype of the virus. Also targets for neutralizing antibodies
Term
T/F Rotavirus is highly contagious.
Definition
true
Term
When does rotavirus infection usually occur?
Definition
late fall, winter and early spring
Term
What is the disease course of rotavirus?
Definition
1-3 day incubation, followed by abrupt onset of vomiting, abdominal cramps, low-grade fever with frequent copious watery stools
Term
T/F Most children are seropositive for rotavirus by age 3
Definition
true
Term
How do you diagnose rotavirus?
Definition
detection of virus particles or viral antigens in the stool
Term
T/F Both rotavirus vaccines are orally administered, non-living virus vaccines.
Definition
false they are live virus vaccines
Term
How was Rotateq developed?
Definition
contains 5 reassortant rotaviruses developed from human and bovine parent rotavirus strains
Term
RotaTeq contians which antigen?
Definition
RV5 pentavalent human-bovine reassortant rotavirus vaccine
Term
What are the doses of rotarix?
Definition
2 doses at 2,4 months of age
Term
What is the antigen used in rotarix?
Definition
RV1 (monovalent human rotavirus vaccine)
Term
When were the two rotavirus vaccines liscensed?
Definition
rotateq in 2006, rotarix in 2008
Term
How was rotarix vaccine created?
Definition
contains a human rotavirus strain isolated from a child; was first attenuated by passaging 33 times in African green monkey kidney cells, then cloned and further passaged in vero cells
Term
T/F The second infection with rotavirus tends to be less severe than the first infection.
Definition
true however niether vaccine nor natural infection will provide full immunity from future infections
Term
What is a possible complication of RotaShield?
Definition
intussusception, taken off the market in 1999
Term
What are the symptoms of colorodo tick fever?
Definition
acute disease with fever headache and severe myalgia
Term
Characterize the genome of the virus that causes colorado tick fever.
Definition
12 double stranded RNA genomic segments
Term
Where is reovirus that causes colorado tick fever found?
Definition
western and northwestern US, western canada; host is the dermacentor andersoni wood tick; natural host are mammals (squirrel, rabbits and deer)
Term
What are the most prevalent and/or significant enveloped RNA viruses?
Definition
influenza, paramyxo, and retroviruses
Term
Name the enveloped RNA viruses that cause CNS disease and hemorrhagic fevers?
Definition
togaviruses (alpha viruses), flavivirus, and bunyaviruses
Term
Name the togaviruses.
Definition
equine encephalitis viruses (EEE, VEE, WEE) chickungunya fever (asia) and rubella (rubi viruses)
Term
Name the flaviviruses.
Definition
yellow fever, dengue, st louis encephalitis, west nile, and hep C
Term
Name the bunya viruses.
Definition
california encephalitis, LaCrosse encephalitis, Rift valley fever, hantavirus
Term
Where are california and laCrosse encephalitis found and what are they transmitted by?
Definition
found in US, transmitted by mosquitoes and chipmunk is a reservoir host
Term
Where is rift valley fever found and what transmits it?
Definition
sandflies in Africa
Term
What are the symptoms of hantavirus infection.
Definition
hemorrhagic fever and pulmonary syndrome
Term
What population does california encephalitis affect most?
Definition
highest rates of disease in children
Term
What time of year is california encephalitis at its peak?
Definition
summer
Term
Does california encephalitis predominantly affect suburban or rural environments?
Definition
vector is found in both places (aedes triseriatus)
Term
Describe the virion of a togavirus.
Definition
SS RNA + enveloped with icosahedral symmetry
Term
How does a togavirus enter a cell?
Definition
via receptor-mediated endocytosis
Term
What is alphavirus?
Definition
insect borne encephalitis
Term
What causes rubella?
Definition
rubivirus
Term
T/F Rubella is insect borne.
Definition
FALSE!
Term
What is the natural host of an alphavirus and how is it transmitted?
Definition
mammal or bird with no apparent disease; transmitted by mosquitoes
Term
Why is is alphavirus only trandmitted by mosquitoes?
Definition
viral replication in gut of vector is essential
Term
Describe the pathogenesis of alpha virus.
Definition
infected arthropod bites and injects virus from salivary glands to capillary bed. Then the virus replicates in the reticuloendothelial system. The systemic phase with symptoms of viremia and fever. Then there is active infection of target tissue (CNS or skin and blood vessels, or viscera and muscle)
Term
What organisms are infected by alphaviral encephalitides?
Definition
found principally in horses (and humans) as accidental dead-end hosts from enzootic transmission from birds or rodents
Term
What are the different types of alphaviral encephalitides?
Definition
EEE (eastern equine encephalitis), WEE (western), VEE (Venezuelan)
Term
Which is the most severe of the alphaviral encephalitides? What's the mortality?
Definition
EEE, 33% mortality with severe neurological sequelae
Term
Where is EEE found?
Definition
EE is very rare but it is found in atlantic and southern coastal states
Term
Where does EEE come from?
Definition
reservoir in birds, possibly pheasants, bird-bird transmission
Term
T/F Most people recover completely from WEE.
Definition
true, there is a 2-3% mortality
Term
What are the symptoms of WEE?
Definition
more frequently symptomatic in children and range from mild flu-like to encephalitis
Term
How is WEE transmitted?
Definition
bird-mosquito-bird
Term
Where is WEE found?
Definition
mostly in western and mid-western states but range of bird and vector rules, so not restricted there
Term
What is the mortality rate of VEE?
Definition
very low (0.5%) in humans but devastating for horses
Term
How is VEE transmitted?
Definition
reservoirs in rodents rather than birds
Term
Where is VEE found?
Definition
chiefly south america and southern US
Term
Where is chickungunya fever found?
Definition
asia, thailand, maylasia, india
Term
What are the symptoms of chickungunya fever?
Definition
debilitating illness with fever, h/a, fatigue, N/V, muscle pain and joint pain
Term
What is the treatment for Chickungunya fever?
Definition
there is no tx or vaccine
Term
What is the viral vector of chickungunya fever virus?
Definition
aedes albopictus
Term
What are the flaviviruses?
Definition
yellow fever, denque, st. louis encephalitis, west nile and hepatitis C
Term
Describe the virion of flaviviruses.
Definition
SSRNA +, enveloped, and icosahedral
Term
What type of virus is yellow fever?
Definition
flavivirus
Term
Which virus type cause encephalitis and hemorrhagic fever?
Definition
encephalitis hemorrhagic fevers
Term
What are the encephalitides of the flavivirus?
Definition
st. louis encephalitis (US-Canada), Japanese B encephalitis (Asia, pigs, and birds) murray valley fever (australia), west nile fever (widespread), powassan virus (North America-tickborne)
Term
Which flaviviruses cause hemorrhagic fevers?
Definition
yellow fever and dengue
Term
What are the symptoms of flaviviral encephalitis?
Definition
fever, h/a, chills, vomiting; drowsiness and nuchal rigidity 1-2 days later. May progress to confusion, convulsion, coma and death
Term
What are the symptoms of yellow fever?
Definition
chills and fever followed by visceral infection of liver and/or kidneys. GI hemorrhage and characteristic black vomit
Term
What is the mortality of yellow fever?
Definition
10%
Term
How can you prevent yellow fever?
Definition
live, attenuated 17D vaccine
Term
What are the natural host of yellow fever?
Definition
monkeys and man
Term
How is yellow fever transmitted?
Definition
sylvatic cycle and urban cycle (human-mosquito-human) cycle; man not necessarily dead-end
Term
Where is Yellow Fever found?
Definition
sporadically in the forested areas of south america and in afra during the rainy season
Term
What is the most widespread arbovirus in the world?
Definition
dengue fever
Term
How many cases of dengue fever are there per year?
Definition
100 million cases/year
Term
Where in the US is Dengue fever found?
Definition
texas and florida keys
Term
Can you be infected with Dengue fever multiple times?
Definition
yes, there are 4 serotypes
Term
How is Dengue fever transmitted?
Definition
between mosquitoes and humans (aedes aegypti). Transmission occurs when mosquito feeds on a person during a 5 day period when large amounts of virus are in the blood
Term
What has caused Dengue to disseminate around the world?
Definition
transport of aedes mosquitoes around the world (WWII)
Term
Where is denque fever found?
Definition
endemic in asia, the pacific, the americas, africa, and the caribbean
Term
What is the time course of the symptoms of Dengue fever?
Definition
begin 4-7 days after the mosquito bite and typically last 3-10 days. Causes severe headache and severe pains in muscle and joints ("breakbone fever") rapidly fading maculopapular rash; hematuria, leukopenia, thrombocytopenia. Convalescence slow but certain
Term
What is Dengue hemorrhagic fever?
Definition
aka dengue shock syndrome. Occurs upon re-infection with another serotype, immune complex type of disease, circulatory shock and hemorrhage, high mortality, esp in children
Term
What is the time course/symptoms of dengue hemorrhagic fever/dengue shock syndrome?
Definition
fever lasts from 2 to 7 days. As fever declines symptoms including persistent vomiting, severe abdominal pain, and difficulty breathing may develop. Capillaries become permeable causing ascites and pleural effusions, leading to shock and death
Term
Dengue epidemics require..
Definition
large number of vector, large numbers of people with no immunity to dengue, the opportunity for contact between the two
Term
How do you tx dengue HF?
Definition
treat symptoms 1) blood/platelet transfusion 2) IV fluids/electrolytes 3) oxygen therapy
Term
What is the prognosis for dengue HF?
Definition
most pts recover with early and aggressive care. Half of untreated pts who go into shock don't survive
Term
Where/when was west nile fever virus found in the US?
Definition
1999, NY metro area
Term
T/F Most humans develop no clinical signs of disease when infected with west nile.
Definition
true (only 20% develop disease of west nile fever)
Term
Which populations have the most severe cases of west nile?
Definition
the elderly
Term
How do you prevent west nile fever?
Definition
aggressive mosquito control (birds are now uniformly infected)
Term
What test is used by blood banks to determine that donated blood does not contain west nile virus?
Definition
nucleic acid amplification test (NAAT)
Term
When are levels of WN virus highest? when are IG levels highest?
Definition
about 3 days before symptom onset
2-3 days post onset
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