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

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

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

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  1. Case Study: Dengue VirusVirology 516Fall 2007Milette 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.Rossmann.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 <100x109cells/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.edu:85/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. 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)

  13. Thank You!!!!!

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