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63 Cards in this Set
- Front
- Back
Why are arboviruses so named?
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Arthropod-borne viruses = Arbovirus
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All arboviruses are transmitted how?
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Bits of arthropod vectors: mosquitoes, fleas, ticks
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Arboviruses include what virus families?
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They're no specific to a family or genus, but include viruses in togaviridae, flaviviridae, and bunyaviridae, and reoviridae
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Analogous to Endemic but with animals (low but constant rate)
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Enzootic
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What are the primary diseases caused by arboviruses?
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Fever, Encephalitis.
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Mneumonic for remembering arboviruses:
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paul BUNYan, about to chop down an ARBOL, wearing a TOGA, with a rich FLAVor attractive to mosquitos
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In incidental host model, How do humans Represent a “dead end” for the virus life cycle in arboviruses?
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although they become ill they do not develop enough viremia to infect new vectors
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When humans are primary vertebrate hosts for the virus, what happens?
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Infection achieves high viremia in human.
vector bites human, moves to another human to vit. Basic cycle is human-vector-human. |
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Eastern Equine Encephalitis (EEE)
Western Equine Encephalitis (WEE St. Louis Encephalitis (SLE) La Crosse Encephalitis (California group) West Nile Encephalitis (WNE) Colorado Tick Fever (CTF) Powassan Fever (POW) Are all examples of what? |
Arbovirus-caused encephalities in North America
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Most severe and potentially fatal of the North American arboviral encephalitides
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Eastern Equine Encephalitis
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Main togaviridae alpha viruses
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Western Equine Encephalitis
Eastern Equine Encephalitis Venezuelan Equine Encephalitis |
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Two diseases caused by bunyaviridae
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La Crosse/California Encephalitis, Rift Valley Fever
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West Nile Encephalitis: What family
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Flaviviridae
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West Nile Vector
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Vector: primarily Culex species mosquitoes
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West Nile Virus is most lethal in what species?
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Birds, horses
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Clinical Manifestations of West Nile
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Most people are asymptomatic.
Some get headache, maculopapular rash. May be followed by fatigue, weakness, difficulty concentrating. Very serious disease may be neuroinvasive (aseptic meningitis, frank encephalitis, weakness, paralysis) |
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Colorado Tick Fever: caused by what?
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Virs that's RNA virus in Reoviridae family
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Primary vector and reservoirs of colorado tick fever
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Vector: Wood tick
Reservoir: Squirrels, chipmunks |
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Powassan Virus: vector, transmission, disease
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Virus: RNA virus in Flaviviridae family
Vector: ticks, 3 Ixodid species and D. andersoni Epidemiology Range is eastern Canada and northeastern US Infection mostly occurs June to September Rare cause of encephalitis, but with high incidence of neurologic sequelae |
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Arboviral Encephalitis:Clinical Features/Symptoms
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With the exception of EEE, all produce similar symptoms of encephalitis
Typical early symptoms include fever, headache, anorexia, nausea/vomiting, myalgias Progression to features of encephalitis – photophobia, severe headache, altered mental status (confusion, disorientation, lethargy), May progress to seizures and coma |
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Arboviral Encephalitis: Diagnosis
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1) Suggested by symptoms and exposure to endemic areas or vectors
2) Mainly serologic: detection of IgM antibody, or 4x rise in IgG antibody on convalescent serum 3) Detection of viral genome sequences in CSF by RT-PCR |
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Arboviral Encephalitis: Treatment
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Mainly supportive. No specific anti-viral agents.
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Eastern Equine Encephalitis: What %age of adults and children develop encephalitis and what is mortality rate?
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2% of infected adults and 6% of children develop encephalitis
Outcome: mortality is 30% with frequent neurologic sequelae in survivors Complete recovery is uncommon |
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Venezuelan Equine Encephalitis (VEE)
Japanese Encephalitis (JE) Tick-Borne Encephalitis (TBE) West Nile Virus (WNV) Murray Valley Encephalitis (MVE) What do they have in common? |
They're arboviral encephalites outside of N America
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Most important global cause of arboviral encephalitis
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Japanese Encephalitis Virus
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Where is Japanese Encephalitis Virus found?
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Across Asia, north Japan, Korea, China, Taiwan, Philippines, Indonesia
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T/F Japanese Encephalitis Virus more severe in adults
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F. More severe in children
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Clinical features of infection
with Japanese Encephalitis Virus |
Only about 1 in 250 infections result in illness
Causes mild febrile illness to frank encephalitis Can also cause acute flaccid paralysis primarily in children |
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T/F Acute flaccid paralysis caused by Japanese Encephalitis virus rarely recovers
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T
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Japanese Encephalitis Virus: Diagnosis and treatment
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Diagnosis is primarily serology.
Treatment is supportive. Mortality in hospitalized patients is 30% |
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Japanese Encephalitis Virus: Prevention
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Formalin-inactivated vaccine is used internationally
A live attenuated vaccine is available in China Vaccine recommended for travelers to endemic countries staying >1month in rural areas or during periods of endemic transmission |
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Tick-Borne Encephalitis: Characteristics
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Virus: RNA virus in Flaviviridae family
Vector: Ixodid (hard) ticks Three geographic subtypes: |
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A benign syndrome caused by several arthropod-borne viruses characterized by biphasic fever, myalgia or arthralgia, rash, leukopenia and lymphadenopathy
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Dengue fever
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Severe, often fatal febrile disease characterized by capillary permeability, abnormal hemostasis and in severe cases, a protein-losing shock syndrome (dengue shock syndrome)
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Dengue hemorrhagic fever
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Arguably most important arthropod-borne viruses from a medical and public health perspective with >100 million human infections year and 2.5 billion at risk
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Dengue viruses
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Dengue virus characteristics
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4 antigenic types (1-4)
RNA Viruses in flaviviridae family |
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Why is Dengue also called Break-bone fever?
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Causes pain backache, muscle and joint pain, and severe headache
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Repeat infection with what serotype predisposes to Dengue Hemorrhagic fever?
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Serotype 2?
"Dengue takes you down in the 2nd round" |
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What is the Dengue virus transmission cycle?
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Human-mosquito-human cycle.
Mosquitos primary vectors. Bite humans. |
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Most dengue disease occurs in what population groups?
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Older children and adults
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What is hyperendemic dengue?
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Continuous circulation of multiple dengue virus serotypes in the same area
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What is the mosquito vector of dengue?
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Aedes aegypti
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Results from introduction of a single virus strain into a region with large population of susceptible hosts and mosquitoes
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Epidemic dengue
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Dengue Fever: Course of Illness
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Incubation period of 1-7 days
Sudden onset of high fever often with frontal or retro-orbital pain Severe back pain may precede fever: “back-break fever” Transient macular generalized rash may be seen in the first 24-48 hours Fever remits after about 6 days, then recurs in 1-2 days with a morbilliform rash Biphasic fever pattern Most patients recover uneventfully |
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Dengue Hemorrhagic Fever: Course of Illness
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Initial phase similar to dengue fever, followed in 2-5 days by rapid clinical deterioration.
Cold extremities, flushed face, diaphoresis, mid-epigastric pain. Coagulopathy: petechiae, ecchymosis (bruise), bleeding from nose and venipuncture sites. May also have maculopapular rash. |
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In what patients does Dengue Hemorrhagic Fever appear?
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Patients who have already had a Dengue infection. Appears to have immunopathologic basis.
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morbilliform : defn
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looks like measles. The rash consists of macular lesions that are red and are usually 2-10 mm in diameter but may be confluent in places.
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Tx of Dengue fever
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Supportive: antipyretics, analgesics, fluids
AVOID aspirin |
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Tx of Dengue hemorrhagic fever
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Intensive care support, IV fluids, maybe Oxygen, Transfusion of blood to control bleeding
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Mortality for Dengue hemorrhagic fever
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30-40% due to hemorrhagic shock syndrome
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Where does Dengue hemorrhagic fever appear most frequently?
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Occurs most frequently in areas where multiple types of dengue virus are simultaneously or sequentially transmitted
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A mosquito-borne viral hemorrhagic fever characterized by hepatic, renal and myocardial injury
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Yellow Fever
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Where does Yellow Fever occur?
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Disease occurs in tropical regions of South America and sub-Saharan Africa
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What family is Yellow Fever in?
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flavivirus
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Transmission of Yellow fever is by
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mosquitos
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3 stages of Yellow Fever infection
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period of infection, period of remission and period of intoxication
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What occurs during First yellow fever stage: Period of Infection?
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Viremia present
Sudden onset fever, headache, myalgias, anorexia, lumbosacral pain and pain in LE Flushing of face and neck, conjunctival injection |
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What occurs during second yellow fever stage: Period of Remission?
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Fever and symptoms abate/resolve.
May last 48 hours. patients with abortive infection recover, 15% ENTER 3RD STAGE. |
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What occurs during third yellow fever stage: Period of Intoxication?
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Viremia resolves and antibodies appear
Return of fever, nausea, vomiting, epigastric pain with jaundice, oliguria and hemorrhage Hepatic dysfunction Renal dysfunction Hemorrhage – prominent feature Myocardial injury CNS dysfunction present in some cases |
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Mortality rate of those who enter third phase
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20-30%
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Yellow fever dx
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Detection of virus by culture, PCR or by serology
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Yellow fever tx
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Symptomatic and supportive
Maintain nutrition to prevent hypoglycemia FFP for bleeding problems Dialysis if needed Treatment of secondary infections |
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Yellow fever prevention
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Live, attenuated vaccine. Recommended for travelers to endemic areas.
Control or avoidance of arthropod vector is mainstay of prevention. |