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72 Cards in this Set
- Front
- Back
for what does arbovirus stand?
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arthropod-borne virus
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are arboviruses normally enveloped or not?
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yes
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typically, what type of nucleocapsid do arboviruses possess? What type of genome?
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icosahedral; +ssRNA
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are all togaviruses and flaviviruses arboviruses?
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no, some are not such as rubella and Hepatitis C
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what is the intrinsic incubation period of the arbovirus? How long is it?
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the human incubation period; usually a week or longer
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what is the extrinsic incubation period of the arbovirus? How long is it?
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the mosquito incubation period; 14 days
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is the mosquito ever harmed by the arbovirus?
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no
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can an arthropod transmit an arbovirus to its progeny? Via which route?
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often, but not always; transovarian
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where are most arboviruses located?
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in the tropics
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what is the only serious arbovirus disease in the USA? Which 5 viruses are responsible?
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encephalitis; Eastern equine encephalitis, Western equine encephalitis, St. Louis encephalitis, West Nile virus, and the California group of encephalitis viruses
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from what does the iniitial viremia in arboviral encephalitis stem?
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multiplication in vascular endothelium
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what is the disease progression of arborviral encephalitis? What is the treatment?
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brief febrile malaise followed by encephalitis with paralysis, coma, and death; no specific treatment available.
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which of the encephalitic arboviruses causes the most severe arboviral encephalitis?
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Eastern equine encephalitis
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does Eastern equine encephalitis affect adults or children more? In addition to humans, which animal is also targeted by the virus?
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children; horses
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which species are dead-end hosts for Eastern and Western equine encephalitis viruses? In addition to mosquitos, which animal is crucial for the propogation of the virus?
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horses and humans; wild birds
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what are 2 good hints of impending Eastern equine encephaitis epidemic?
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excessive rainfall and abnormally high mosquito populations
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what are the 2 standard control measures against Eastern equine encephalitis?
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reduction of mosquito population and avoidance of mosquitoes during epidemic
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St. Louis encephalitis virus and West Nile virus are both members of which virus family? Are they antigenically similar?
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flavivirus; yes
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in which population are SLE and WN viral infections mostly fatal?
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elderly
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why are humans considered dead-end hosts for SLE and WN viral infections?
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they rarely have viremia high enough to infect mosquitos
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how are SLE and WN viral epidemics maintained?
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via bird->mosquito->bird cycles
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to which region of the world is SLE indigenous? WN virus?
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North America; North Africa and Middle East
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of Eastern encephalitis, Western encephalitis, WN virus, SLE, and LaCrosse virus, which is the most fatal?
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Eastern equine encephalitis
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what kind of birds are responsible for maintaining an epidemic of Eastern and Western equine encephalitis? SLE and WN virus?
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wild birds; domestic and wild birds
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Eastern and Western equine encephalitis are both members of which viral family?
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togavirus
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are arboviral epidemics in the temperate regions of longer or shorter duration than those in the tropics?
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shorter
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what are 2 diseases, other than encephalitis, that are attributed to arboviral infections?
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yellow fever and dengue fever
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is dengue fever usually life-threatening? What are the symptoms?
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no; fever, severe headache, muscle and joint pain, rash
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what is the incubation period for dengue fever? Where is it most commonly found?
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1 week; in the tropics and subtropics, especially SE Asia and Caribbean islands
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how many different antigenic types of dengue virus exist? Do they cross-react?
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4; yes
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are humans dead-end hosts for dengue viral infections?
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no
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what symptoms characterize dengue hemorrhagic fever? Is this seen more in the native or visiting population?
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hemorrhage, vomiting blood, and shock; native
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what is the underlying mechanism behind hemmorhage in dengue hemorrhagic viral infections?
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macrophage infection causes increase in lymphokines and cytokines which causes hemorrhage
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how long is the incubation period for yellow fever?
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5 days
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where does yellow fever virus first multiply in the host? Where does it spread from there?
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vascular endothelium; liver and other organs
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what symptoms characterize yellow fever?
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fever, nausea, jaundice
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in addition to the liver, where does yellow fever viral multiplication occur?
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in spleen and kidney
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are there subclinical infections of yellow fever? Is the mortality for yellow fever high?
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yes; high
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where is yellow fever found now?
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in rural tropical Africa and South America
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which species of mosquito is the arthropod host for dengue and yellow fever?
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Aedes Aegypti
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other than mosquitoes, which animal is responsible for the spread of jungle yellow fever?
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monkey
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Is there a vaccine available for yellow fever? What type of vaccine is it?
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yes, D17; live-attenuated
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what is the risk of an unvaccinated person entering during a yellow fever incubation period? Where is this a problem right now?
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the virus may spread to the mosquitoes then to the susceptible population; in the southeastern US
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what are vertical infections? Horizontal infections?
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infections transmitted from mother to progeny; all other infections
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what are the 2 pathways that lead to vertical infections?
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perinatal and transplacental
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which viruses are perinatally acquired?
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HBV, HIV, herpes simplex type 2
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what are the implications of transplacental infections? What are 4 examples of viruses transmitted in this manner?
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they can result in congenital abnormalities due to interference with normal development; parvovirus B19, rubella, cytomegalovirus, and lymphocytic choriomeningitis
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are embryonic cells and embryos good hosts for viral growth?
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yes, but this is prevented by the placenta
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how do transplacental infections cross the placenta?
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by replicating in placental tissue
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what are fetal defense mechanisms against viral infections?
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maternal IgG, fetal Ab after 4th month, inteferon, and cell-mediated immunity
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are parvovirus virions enveloped? What is their capsid symmetry? Their genome?
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no; icosahedral; linear ssDNA
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what is the route of infection of parvovirus B19?
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inhalation of a respiratory aerosol from the resp tract of an infected person
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what are the symptoms of a parvoviral infection?
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atymptomatic or fever, malaise, rash called erythema infectiosum
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what is the likely cause of the rash which presents in parvoviral infections?
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deposition of immune complexes in capillaries
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for which cell type does parvovirus B19 have a tropism? What impact does the initial infection have on the host?
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erythroid precursors; inhibition of RBC production for about a week
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how well do normal people tolerate the cessation of RBC production in parvoviral infections?
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just fine
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what occurs during the beginning of a parvoviral infection in hosts with a pre-existing deficit in red blood cell production or a pre-existing abnormally high rate of red cell destruction?
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they will have a transient aplastic crisis which can be fatal without transfusions
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what chronic condition can result in patients that are unable to fight the parvoviral infection? What treatment is used for these patients?
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prolonged anemia; immunization with pooled IgG
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what is the most common symptom in primary parvoviral infection?
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acute arthritis
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what symptom is unique to first- and second-trimester parvoviral infections in developing fetuses?
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hyrops fetalis
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to what family of viruses does rubella belong? It is transmitted via arthropod infection?
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togavirus; no
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how is rubella virus transmitted?
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by respiratory aerosols from the resp tract of an infected person. Local multiplication in the resp epithelium is followed by viremia
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which is more contagious, rubella or measles virus?
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measles virus
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how long is the incubation period for rubella virus? Is rubella ever subclinical?
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18 days; yes
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how long does the rubella rash last? What other symptoms are present at this time?
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3 days; fever and lymphadenopathy
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when, in relation to the rash, is rubella virus excreted from the respiratory tract?
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one week before and after the rash
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what symptom of severe rubella viral infections is seen in adults?
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transient arthritis
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what congenital anomalies can result from a transplacental rubella infection?
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cataracts, heart defects (patent ductus arteriosus), deafness, retardation
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does deafness associated with congenital rubella worsen during life?
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yes, it may not be obvious at birth but becomes progressively worse in early years of life
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what is the main purpose of the live rubella vaccine?
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to prevent congenital rubella
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in addition to children, who else should receive the rubella vaccine?
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seronegative women of child-bearing age
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is rubella still a public health problem in developing countries?
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yes
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