Dengue Disease

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University of Oklahoma Study Abroad Microbiology in Arezzo, Italy[1]

Etiology/Bacteriology

Taxonomy

Group = Group IV positive-sense ssRNA virus | Order = Unassigned | Family = Flaviviridae | Genus = Flavivirus | species = Dengue Virus

NCBI Taxonomy: (DENV-1) (DENV-2) (DENV-3) (DENV-4) Genome: Dengue Virus

Description

Dengue (pronounced DENgee) viruses belong to the family Flaviviridae, genus Flavivirus. There are four serotypes: DENV-1, DENV-2, DENV-3, and DENV-4, which belong to a larger, heterogeneous group of viruses called arboviruses. This is an ecological classification, one which implies that transmission between vertebrate hosts, humans, is dependent on hematophagous arthropod vectors. Dengue fever is transmitted by the bite of an Aedes mosquito infected with a dengue virus. The mosquito becomes infected when it bites a person with dengue virus in their blood. It can’t be spread directly from one person to another person. Dengue fever is a painful, debilitating mosquito-borne disease. This virus is related to the viruses that cause West Nile infection and yellow fever. Each year, an estimated 100 million cases of dengue fever occur worldwide, with most of these cases occurring in tropical areas of the world. [1]

The Dengue Virus is considered an Old Disease, which goes back to the Chin Dynasty (AD 265–420), where it was first recorded. There are reports of epidemics of dengue-like illnesses in the French West Indies in 1635 and in Panama in 1699. By the late 1700s, the disease had a worldwide distribution in the tropics: Indonesia, Egypt, and in 1780 in Philadelphia. From the late 1700s to World War II, repeated epidemics of dengue illness occurred in most tropical and subtropical regions of the world.

Pathogenesis

Virulence factors

Dengue

Like all Gram negative bacteria, EHEC outer membranes have an outer facing leaflet of lipopolysaccharide (LPS). LPS consists of lipid A, core polysaccharide, and O-Antigen, which consists of 40-80 repeating subunits of 4 sugars that in the case of E. coli O157:H7 is unique to the O157 serogroup, containing N-acetyl-d-perosamine, l-fucose, d-glucose, and N-acetyl-d-galactose. The core polysaccharide essentially is conserved in all E. coli ecotypes. Lipid A is the toxic component of LPS, also known as endotoxin, which is a heat-stable toxin. Lipid A consists of a phosphorylated disaccharide of glucosamine linked by a beta-1,6 linkage and modified by fatty acids, in addition to the first ketodeoxyoctanoate of the core polysaccharide. Endotoxin is released by cell lysis rather than being secreted. Endotoxin is less potent and less specific than exotoxins. Endotoxin can cause fever, hemorrhagic shock, and diarrhea.

References

Created by Brandon Kitchens, students of Tyrrell Conway at the University of Oklahoma.

1 Karriem-Norwood, Varnada, MD. "Dengue Fever: Symptoms, Causes, and Treatments." WebMD. WebMD, 20 Sept. 2012. Web. 24 July 2015