Case Study: Dengue Virus Virology 516 Fall 2007 Milette Mahinan, Suzi Sanchez, Olayinka Taiwo - PowerPoint PPT Presentation

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Case Study: Dengue Virus Virology 516 Fall 2007 Milette Mahinan, Suzi Sanchez, Olayinka Taiwo

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Title: Case Study: Dengue Virus Virology 516 Fall 2007 Milette Mahinan, Suzi Sanchez, Olayinka Taiwo


1
Case Study Dengue VirusVirology 516Fall 2007
Milette Mahinan, Suzi Sanchez, Olayinka Taiwo
2
Dengue Virus Morphology
  • Dengue virus is a small, spherical,single
    stranded enveloped RNA virus
  • Belongs to the family Flaviviridae

Http//news.uns.purdue.edu/html4ever/030618.Rossma
nn.immature.html
3
Case Study Information
  • Victim a 30 year old woman
  • Symptoms fever, backache, headache, myalgias in
    the upper arms, pain on moving her eyes,
    blanching erythematous rash on face, arms, trunk,
    and thighs,
  • Possible exposure area had returned home from
    trip to El Salvador where she had extensive
    exposure to mosquitoes
  • Other physical characteristics no enanthem,
    murmur, of splenomegaly
  • White blood cell count 1600/µl with a normal
    differential
  • Platlet count 140,000/µl
  • Hemoglobin 17.5g/dl
  • Convalescent phase antibodies tested positive for
    dengue virus

4
By what type of mosquito is this virus
transmitted?
  • Aedes aegypti mosquito
  • Small in comparison to other mosquitoes
  • Found in the tropics (dengue is the second most
    frequent cause of hospitalization among travelers
    returning from the tropics)
  • Some presence in the lower half of Florida

5
Dengue Hemorrhagic Fever (DHF)
  • Dengue may appear as a severe and fatal disease
    called DHF.
  • DHF is defined by 4 criteria according to the
    world health organization
  • 1) fever or history of fever lasting 2-7 days
  • 2) a hemorrhagic tendency shown by a positive
    tourniquet test or spontaneous bleeding
  • 3) thrombocytopenia (platelet count
    lt100x109cells/L)
  • 4) evidence of plasma leakage shown by
    hemoconcentration with substantial changes in
    serial measurements, or by packed cell volume
  • Note hemorrhagic manifestations without
    capillary leakage do not constitute DHF
  • Wilder-Smith, Ananth Tambyah (2007)

6
Other clinical Manifestations
  • Petichial rash on extremities such as, the
    forehead
  • the capillaries become excessively permeable, may
    lead to plasma leakage
  • Shock- due to rapid and weak pulse, may lead to
    DSS
  • Hapatomegaly (enlargement of the liver)- observed
    mostly in children living in Thailand.
  • In severe cases, circulatory failure, which if
    left untreated can result in death within
    12-24hrs
  • nevertheless, people can recover following
    appropriate volume replacement therapy of the
    circulating fluid in the body

7
Dengue has 4 serotypes
  • These are known as DEN-1,DEN-2,DEN-3, and DEN4
  • A viral serotype is distinguished by protein or a
    protein component that determines its antigenic
    specificity
  • Each viral serotype has characteristics that
    determine the nature of the epidemic and disease
    severity
  • Nisalak et al.(2003)

8
Secondary Infection
  • It is common to see more serious symptoms related
    to secondary infection
  • Secondary infection occurs when a person is
    infected with a serotype distinct from the one
    that caused the initial infection
  • The predominant serotype causing an epidemic may
    vary by year and geographic location
  • DEN-1,2,3 are associated with moderately severe
    epidemic years
  • Only DEN-3 is associated with severe epidemic
    years
  • DEN-2,3 are associated with severe symptoms, DHF
  • Epidemics by multiple serotypes hyperendemicity
  • Nisalak et al.(2003)
  • http//en.wikipedia.org/wiki/Dengue_fever

9
Subcutaneous hemorrhage on a DHF patient
http//www.med.sc.edu85/mhunt/arbo.htm
10
Will primary infection confer immunity to other
serotypes????
  • It is known that immunity to the same serotype is
    long lasting (refers to the serotype causing the
    initial infection)
  • Immunity to a second serotype is at best
    transient
  • Based on the current information, it can be
    predicted that immunity to one serotype does NOT
    confer immunity to others that exist, or new ones
    that may arise
  • Rothman(2007)

11
Dengue endemic regions
  • The disease is now endemic in more than 100
    countries in
  • Eastern Mediterranean
  • South-east Asia
  • Pacific Islands
  • Central and South America
  • Carribean
  • Africa
  • WHO currently estimates that there may be 50
    million cases of dengue infection worldwide every
    year
  • http//www.who.int/mediacentre/factsheets/fs117/en
    /

12
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13
Preventive measures for travelers
  • Use mosquito repellents containing DEET
  • Use mosquito nets
  • Insecticides
  • Wear protective clothing
  • Avoid being outdoors during the early morning and
    late afternoon (feeding times of the Aedes
    aegypti mosquitoes)

14
Thank You!!!!!
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