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70 Cards in this Set
- Front
- Back
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Where in the world is dengue
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everywhere
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How is dengue spread to other regions?
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possibly transported by standing water carrying mosquitos (e.g.tires)
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What is the most important mosquito transmitted viral dz?
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Dengue (for morbidity/mortality)
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What percent of the world is at risk for dengue?
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30%
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What's going on with Dengue in Americas?
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50 fold increase from 1980s to 1990s
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How many dengue serotypes are there?
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4
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Which is the most widespread arbovirus?
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Dengue
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Does dengue have a zoonotic cycle?
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Used to…but now adapted to human and only NEEDS human host.
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What mosquito spreads dengue?
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Aedes aegypti (tiger mosquito with white bands); early morning/early evening biter
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Why has dengue emerged as a major pub health problem?
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1. Uncontrolled urbanization/pop growth; 2. Inadequate water/waste mgmt; 3. Crisis mentality 4. Untrained medical folks 5. Airline travel spreads 6. Non-existent mosquito control programs for dengue (ultra low volume insecticide sprays ineffective)
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Where is 70% of dengue found?
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The americas
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How did aedes aegypti become so prevalent in Americas after 1970?
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End of mosquito control program
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Which is the most virulent dengue serotype?
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DEN-2 (aeared first in americas in 1970s)
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Which dengue serotype caused the first DHF epidemic in americas?
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DEN-2 -- a new strain from SE Asia -- introduced in 1981
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Is dengue endemic in Latin america?
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Yes, in recent decades
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Describe the dengue virus
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Arbovirus; RNA single stranded; 4 serotypes;
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Which dengue serotype is severe/fatal?
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All can cause severe/fatal dz; some serotypes have more severe genetic variants
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What are the common dengue vectors?
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Aedes aegyptii and Aedes albopictus
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Where does Aedes aegyptii like to lay eggs?
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In artificial containers
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What are the 4 dengue syndromes?
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Undifferentiated fever, Dengue fever, Dengue Hemorrhagic Fever, Dengue Shock Syndrome
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Clinical sx of dengue fever?
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Fever, H/A, myalgias/arthralgias, N/V, rash, hemorrhagic manifestations, METALIC TASTE, severe depression in recovery phase
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Case fatality rate of Dengue?
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5% (up to 30% with inadequate mgmt)
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Who is more likely to die of dengue?
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Children, young adults
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What is the incubation period for dengue?
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4-7days; viremia starts just before sx onset
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How long does dengue viremia last?
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5 days
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How long is one symptomatic with dengue?
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3-10 days -- so clinical illness longer than viremia
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What is the clinical case definition for dengue?
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Acute febrile viral dz, presenting with h/a, bone/joint apin, myalgias rash and LEUKOPENIA
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What are the 4 criteria necessary for DHF?
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Fever (or recent history), hemorrhagic manifestations, platelets <100,000, objective leaky capillaries (elevated ematocrit >20% above baseline), low albumin, pleural/other effusions)
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What are the typical blood manifestations of DHF?
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Low platelets, low WBC, high hematocrit (sometimes >20% higher than normal)
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What are the 4 WHO grades of DHF?
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1. Fever/nonspecific sx, + tourniquet test/petechiae; 2. Grade one + spontaneous bleeding 3. Signs circulatory failure (shock -- narrowed pulse pressure <20mmHg, hypotesnsion, cold/clammy skin) 4. Profound shock (no pulse/BP)
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What test should be done on all people with suspected dengue?
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Guiac to detect blood in stool (early hemorrhagic…)
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How to do a tourniquet test?
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Inflate between SBP/DBP for 5 min. >20 petechia per square inch is positive
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What is a classic sign of DHF?
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Islands of white, occur with dengue recovery
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What is a pleural effusion index?
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PEI = A/Bx100 (the percentage of effusion)
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When is pleural effusion seen in dengue?
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The day after defervescence
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What are warning signs in DHF?
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Abdominal pain, persistent vomiting, abrupt change from fever to hypothermia, restlessness/somnolence (signs of impending shock)
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What might be the first sign of Dengue Shock Syndrome?
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Delayed cap refill
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What is the case definition of DSS?
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DHF criteria plus circulatory failure (rapid/weak pulse, narrow pulse pressure (<20mmHg), cold clammy skin, AMS)
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What is the treatment for a child in DIC?
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Crystalloid fluid resuscitation and "standard DIC treatment"
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What is the word used for dengue pathogenesis?
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Peculiar
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Is there cross protection between dengue serotypes?
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No; antibodies to one type increases risk DHF/DSS however
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Are primary dengue infections normally fatal?
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No, but can be debiltating. Normally a second infection leads to DHF/DSS
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Why is dengue worse a second time?
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Antibody dependent enhancement
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What is antibody dependent enhancement?
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Certain strains of dengue, complexed with non-neutralizing antibodies, can enter a greater proportion of cells of mononuclear lineage thus INCREASING viral production. Infected monocytes release vasoactive mediators, resulting in increased vascular permeability and hemorrhagic manifestations that characterize DHF and DSS.
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Is it the virus that causes the severe sx of DHF/DSS?
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No, it’s the immune resonse (vasoactive mediators cause increased vascular permeability)
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What's going on with neutralizing antibodies and dengue?
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With first infection, neutralizing antibodies complex with virus and neutralize it. With subsequent infection, heterologous antibodies do not neutralize the new virus. Non-neutralizing antibody/virus complexes are opsonized, leading to higher viral uptake by monocytes/macrophages, and increased viral production
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What is original antigenic sin?
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Neutralizing antibodies are strongest for oringal dengue serotype
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Has there ever been seen DHF on a first infection?
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Yes, very rarey. Makes the "ADE" -- antibody-dependent enhancement -- theory questioned
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Can infants have preexisting anti-dengue antibodies?
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Yes, from maternal antibodies
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Is race a factor in DHF?
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Yes, whites get more (in Cuba this has been seen)
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Which ages are at risk?
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In SE asia, children; elsewhere, all ages affected
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Which viral serotypes are highest for DHF?
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In this order: DEN 2, 3, 4, 1
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Where is DHF more likely?
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In hyperendemic areas -- due to risk of a second infection, and increased viral circulation (increased virulence risk)
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What lab tests done for dengue?
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CBC, albumin, lfts, U/A (for hematuria), guiac; Dengue specific: ELISA; acute and convalescent phase sera; tissue culture (fluorescence)
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Is there an elisa test for dengue?
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Yes
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Is there a rapid bedside test for dengue?
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Yes
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How to manage dengue?
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No hemorrhagic sx: go home. Hemorrhagic/dehydration: observe; Warning signs of DHF/DSS: hospitalize
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When is risk for DHF gone?
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7 days into illness -- if no sx of DHF, risk gone
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What days of DF are at risk for DHF?
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Days 3-6 greatest risk
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When is it common for shock to occur in DF?
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After fever gone
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What is the treatment for dengue?
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Supportive care; prevent shock
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What blood tests are recommended in Dengue follow-up?
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Serial hct/platelets until normal temp for 1-2d for DHF; repeat blood test in convalescent phase (6-30d)
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What drugs to avoid in DF?
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ASA, NSAIDS!
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Do patients with DF need mosquito control?
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Yes, to prevent spread, avoid mosquitos while febrile
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Does dengue + bleeding = DHF
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No, must have the 4 WHO criteria (fever, non-specific sx + tourniquet test, spontaneous bleeding, signs circ failure)
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What is "among the most dramatic events in clinical medicine"?
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The rapid clinical response of children with DHF/DSS to fluid resuscitation
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What sx common in convalescent phase of dengue?
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Weakness, mental depression, bone pain, BRADYCARDIA, PVCs
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Is there a dengue vaccine?
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No…must be tetravalent or puts folks at risk for DHF! Field testing underway
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How to eliminate dengue mosquitos?
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Cover water containers, seal septic tanques, remove rubbish, biological control (fish eating larva), chemical control
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How does a reliable water supply help prevent dengue?
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Stops people from storing water
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