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Dengue

Dengue. Virus, Vector and Epidemiology. I. Virus. Dengue Virus. Causes dengue and dengue hemorrhagic fever Is an arbovirus Transmitted by mosquitoes Composed of single-stranded RNA Has 4 serotypes (DEN-1, 2, 3, 4). Dengue Viruses.

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Dengue

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  1. Dengue Virus, Vector and Epidemiology

  2. I. Virus

  3. Dengue Virus • Causes dengue and dengue hemorrhagic fever • Is an arbovirus • Transmitted by mosquitoes • Composed of single-stranded RNA • Has 4 serotypes (DEN-1, 2, 3, 4)

  4. Dengue Viruses • Each serotype provides specific lifetime immunity, and short-term cross-immunity • All serotypes can cause severe and fatal disease • Genetic variation within serotypes • Some genetic variants within each serotype appear to be more virulent or have greater epidemic potential

  5. Extrinsic incubation period Illness Illness Transmission of Dengue Virusby Aedes aegypti Mosquito refeeds / Mosquito feeds / transmits virus acquires virus Intrinsic incubation period Viremia Viremia 0 5 8 12 16 20 24 28 Days Human #1 Human #2

  6. 1 2 4 3 Replication and Transmissionof Dengue Virus (Part 1) 1. Virus transmitted to human in mosquito saliva 2. Virus replicates in target organs 3. Virus infects white blood cells and lymphatic tissues 4. Virus released and circulates in blood

  7. 6 7 5 Replication and Transmissionof Dengue Virus (Part 2) 5. Second mosquito ingests virus with blood 6. Virus replicates in mosquito midgut and other organs, infects salivary glands 7. Virus replicates in salivary glands

  8. II. Vector

  9. Aedes aegypti Mosquito

  10. Aedes aegypti • Dengue transmitted by infected female mosquito • Primarily a daytime feeder • Lives in and around human habitation • Lays eggs and produces larvae preferentially in artificial containers

  11. Aedes aegypti Breeding Sites

  12. III. Epidemiology

  13. Areas infested with Aedes aegypti Areas with Aedes aegypti and recent epidemic dengue World Distribution of Dengue1999

  14. Reported Cases of Denguein the Americas, 1980 - 1998 *Provisional data for 1998

  15. Mean Annual Number of DHF CasesThailand, Indonesia and Vietnam, by Decade * Provisional data through 1998

  16. Reported Cases of DHF inthe Americas, 1970 - 1998 * Provisional data through 1998

  17. Distribution of DEN-3in the Americas, 1998 1994 1995 1997 1998 Pan American Health Organization, 1999

  18. Recent Dengue in the U.S.A. (Texas) • Dengue epidemics occurred in the USA in the 1800s and the first half of the 1900s • Recent indigenous transmission: • 1980: first locally acquired cases since 1945 • 1986: 9 cases • 1995: 7 cases • 1997: 3 cases • Lack of recent epidemic transmission likely due to changes in life style

  19. Reasons for Dengue Expansion in the Americas • Extensive vector infestation, with declining vector control • Unreliable water supply systems • Increasing non-biodegradable containers and poor solid waste disposal • Increased air travel • Increasing human population density in urban areas

  20. Challenges for the Future • 2.5 billion people at risk world-wide • In the Americas, 50-fold increase in reported cases of DHF (1989-1993 compared to 1984-1988)* • Widespread abundance of Aedes aegypti in at-risk areas * Organization of American States, Human Health in the Americas, 1996

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