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77 Cards in this Set
- Front
- Back
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What does arbovirus stand for?
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Anthropod-borne virus
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Give three examples of arbovirus groups.
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Togaviruses (equine encephalitis)
Flavivirus (St. Louis encephalitis and west nile virus) Bunyaviruses (do not need to know any detail) |
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Togaviruses and flaviviruses share which of the following characteristics: (one or more answers)
a. large b. unenveloped c. icosahedral nucleocapsid d. single molecule of (-)stranded RNA e. most toga-and flavi-viruses are arboviruses |
a. No- small
b. No c. Yes d. No- single (+)stranded RNA e. Yes |
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Define intrinsic and extrinsic incubation periods.
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Transmission of arboviruses requires multiplication in the arthropod host. Thus, there are two incubation periods:
a. Intrinsic incubation period in humans: ~1wk or longer b. Extrinsic incubation period in mosquito or other anthropod: ~14 days during whicn the arbovirus is multiplying in the anthropod. |
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Name 6 arboviruses that cause encephalitis.
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Eastern equine encephalitis virus (EEE)
Western euqine encephalitis virus (WEE) St. Louis encephalitis virus West Nile virus California group of encephalitis viruses Venezuelan equine encephalitis virus (VEE) |
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How long is the intrinsic incubation period in arboviral encephalitis?
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~ 1wk, relatively short for verimic infection
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True or false:
Following the incubation period, the initial viremia results from multiplication in vascular endothelium. |
True
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Which virus causes the most deadly arboviral encephalitis?
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Eastern equine encephalitis
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How is EEE transmitted to the dead-end hosts, i.e. humans and horses?
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When a mosquito bites a viremic wild bird, the EEE multiply in the mosquito. When the mosquito bite a human the virus is trasmitted.
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True or false:
The best warning of impending EEE epidemics comes from finding a high prevalence of antiviral antibody in wild birds. |
True
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What are the standard controls during the EEE epidemic?
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a. reduction of mosquito population
b. avoidance of mosquitoes during epidemic (e.g. insect repellent) |
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To which group(s) of viruses do West Nile virus and St. Louis virus belong?
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Flaviviruses (single (+)stranded RNA)
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Are humans dead-end hosts for St. Louis encephalitis and West Nile viruses?
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Yes
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True or false:
St. Louise encephalitis and West Nile viruses are found only in the mosquito of rural areas. |
False.
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True or false:
St. Louis and West Nile viruses are fatal in most cases. |
False. ~10% of the clinical cases are fatal. Many are subclinical.
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True or false:
Western equine encephalitis virus infection is often fatal. |
False. ~10% of the clinical cases are fatal. Many are subclinical.
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True or false:
Eastern equine encephalitis virus infection is often fatal. |
True. ~75% of clinical cases are fatal. Some are subclinical infections.
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True or false:
Adults over 50yo is the dangerous age group for St. Louis encephalitis. |
True
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True or false:
Adults over 50yo and infants are the dangerous age group for West Nile virus infection. |
False. The adults over 50 is the age group with highest incidence.
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True or false:
Infants and adults over 50 yo have a high incidence of Western equine encephalitis. |
True
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True or false:
Eastern equine encephalitis occurs mostly in school-age children. |
False- mostly children under 10.
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LaCrosse virus has a high incidence in which of the following age group?
a. children b. children under 3 yo c. adults over 50 yo d. all populations |
a. children
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What are the major vertebrate hosts for LaCrosse virus?
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Hares and rodents
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Where is the habitat of major mosquito vector for LaCrosse virus?
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Rural forest
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To which virus group does LaCrosse virus belong?
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Bunyavirus- enveloped RNA virus (no further detail discussed in this course)
Also, it is a member of the California encephalitis virus group. |
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True or false:
In the temperate zones, arbovirus disease is seen as focal epidemics of short duration. |
True. The conditions have to be just right to allow transmission.
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True or false:
Outside the USA, arboviruses cause yellow fever or dengue fever, in addition to encephalitis. |
True- both are flavivirus
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Is classical dengue fever a life-threatening disease?
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No, although it is a severe disease (a.k.a. "bone-break fever") it is NOT life-threatening.
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Where does dengue fever occur most commonly?
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in south east asia and the Caribbean islands
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Are humans dead-end hosts for yellow fever or dengue flaviviruses?
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No
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Recently in SE Asia and the Caribbean, there has emerged a hemorrhagic dengue fever. Is this a fatal form? What are the characteristics that distinguish a hemorrhagic dengue fever from a classical form?
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The hemorrhagic dengue fever is fatal and is characterized by hemorrhage, vomitting blood and shock.
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A patient who travelled to the Carribean for spring break has been diagnosed with a dengue fever. Would you expect this patient to have a classic or a hemorrhagic dengue fever?
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Most visitors get the classical mild disease. Although there has been no hard evidence it is likely that sequential infections with two different serologically cross-reacting dengue viruses would cause the hemorrhagic dengue fever.
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How many corss-reacting antigenic types of dengue virus are there? What are they?
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4 cross-reacting antigenic types (type 1,2,3,4)
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How long is the incubation period for dengue fever virus?
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one week
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What are the common symptoms of a classical form?
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Muscle pain
and rash |
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How long is the incubation period of yellow fever?
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~7 days
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What are the symptoms of yellow fever?
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Characterized by fever, nausea and jaundice (from viral damage to liver cells).
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Where is the initial multiplication site of the flavivirus causing yellow fever?
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In vascular endothelial cells and the resultant viremia serves to infect the liver and other organs such as spleen and kidney.
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How is the mortality rate of yellow fever?
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High
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Where are yellow fever found?
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Rural tropical Africa and South America
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Describe the pattern of transmission for yellow fever or dengue
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-> Aedes aegypti (mosquito) -> humans -> Aedes aegypti -> humans
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Jungle yellow fever has another cycle perpetuating the virus in tropical forests. What are the agents participating in this cycle?
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-> monkey -> tree mosquito-> monkey -> tree mosquito -> humans -> Aedes aegypti -> humans
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Is there a vaccine available for yellow fever?
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Yes, an excellent live-attenuated vaccine (17-D vaccine) gives long-term protection.
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What alert(s) the danger of yellow fever epidemics?
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Aedes aegypti and unvaccinated person
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Define:
a. vertical infection b. horizontal infection |
a. neonatal infections acquired from the mother
b. all other infections than vertical infections |
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What are two pathways that lead to vertical infection?
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(a) perinatal pathway: neonate infected during birth by contact with maternal blood or other fluids. Similar to horizontal pediatric infections (b) transplancental pathway: the virus crosses the placenta to invade the developing fetus. Often distorts normal development resulting in congenital anomalies.
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Which viruses can neonates contract in the perinatal pathway?
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HBV, HIV and herpes simplex type 2
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Which viruses can fetus contract in the transplacental pathway?
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Parvovirus B-19
Rubella virus Cytomegalovirus Lymphocytic choriomeningitis virus |
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Is fetal infection common? Why or why not?
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Fetal infections are uncommon because the placenta is a barrier to most viruses. Even the smallest viruses are impermeable across the placenta. But some viruses replicate in placental tissue.
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Are most maternal viral disease threat to fetus?
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No, as a substantial defense mechanisms, the developing fetus is well-protected against viral infections.
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What are the substantial defense mechanisms a fetus use against viruses?
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a. maternal IgG
b. Fetal antibody after fourth month (mostly IgM) c. Interferon (probably adequate after 4 mo.) d. Cell-mediated immunity |
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Parvovirus B-19
Enveloped or uneveloped Nucleocapsid symmetry Genome |
Unenveloped
Icosahedral virions Linear single-stranded DNA But little nucleotides to replicate its genome |
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What is the route of Parvovirus B-19 infection?
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Inhalation of a respiratory aerosol from an infected person
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What is the major damage done by the parvovirus-19?
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The infection inhibits red blood cell production for about a week, by viral growth in the red blood cell precursors.
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Which groups of patients are susceptible to fatal crisis during the parvovirus B-19 infection?
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a. Patients with pre-existing deficits and abnormalities in red cell production.
b. Fetus |
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True or false:
Primary B-19 virus infection during pregnancy can lead to fetal death only in the 1st trimester. |
False. Primary B-19 virus infection during pregnancy can lead to fetal death no matter when in gestation the infection takes place.
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Fill in the blank:( ) is associated with fetal death caused by B-19 infection in the 1st and 2nd trimester.
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Hydrops fetalis (severe edema). Infection in the third trimester can result in intra-uterine fetal death but hydrops is not seen.
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Fill in the blank:
Rubella virus is a ( )-virus. |
togavirus
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What is the main route of rubella virus transmission?
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Rubella is transmitted by respiratory aerosols from an infected person. Unlike other togaviruses (e.g. EEE, VEE and WEE), there is no anthropod transmission.
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Is viremia involved in the infection of rubella virus?
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Yes, local multiplication in the respiratory epithelium is followed by viremia.
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Which is less contagious: measles or rubella?
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Rubella. There are persistence of seronegative adults.
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How long is the incubation period for rubella?
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18 days
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What are the typical symptoms of rubella?
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Rash that lasts about 3 days with a fever and lymphadenopathy
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When are rubella-infected individual infectious?
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One week before and after the rash. Sometimes rubella is subclinical.
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True or false:
Rubella is sometimes more severe in adults, with transient arthritis. |
True
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Does subclinical infections of rubella virus produce lifelong immunity?
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Yes
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Is there a vaccine for rubella?
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Yes, there is a live vaccine. It has been successful, and now rubella is very rare.
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What is the cause of congenital rubella?
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Rubella virus from the viremia of primary infection during pregnancy croses the placenta.
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In addition to spontaneous abortion, spectrum of possible congenital anomalies are:
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a. cataracts
b. heart defects, especially patent ductus arteriosus c. deafness d. retardation |
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The time of fetal infection of rubella virus is critical. Explain the statement.
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Infection during the first month of gestation, 50% malfomration. 2nd month 25%. third month 9% and fourth month 4%.
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True or false:
Rubella is not fatal in most people but its vaccination is important in creating a herd immunity because congenital rubella can have a severe consequence to a developing fetus. |
True
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True or false:
Virus production throughout gestation and gradually decreasing through first two years of life (mostly in urine) |
True
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In order to create herd immunity, two conditions are pursued in the United States. What is the plan?
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a. nearly all children must be immunized
b. Individual immunity must be maintained through the child-bearing years to reduce the number of susceptible pregnant women. |
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What would you recommend about pregnancy for seronegative women of child-bearing age getting the vaccine?
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To avoid pregnancy for two months.
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Has there been reported cases of transplacental infection or congenital anomalies in vaccinated pregnant women?
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No
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Which group of individuals are susceptible to congenital rubella nowadays?
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a. children whose parents do not allow immunization
b. rubella cases in immigrant children c. sero-negative women of child-bearing age |
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True or false:
The use of MMR vaccine eradicated rubella, and rubella is no longer a major public health concern. |
False: Rubella remains a major public health problem in many developing country.
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