Flaviviriae

Properties of Fiaviviridae 434

Pathogenesis and Clinical Features 436

Laboratory Diagnosis.. ^... 437

Epidemiology and Control 438

Yellow Fever 438 <

Dengue 441 i

Flavivirus Encephalitideis 443

Tick-Borne Flavivirus Hemorrhagic Fevers 445

Hepatitis C 445 |

Further Reading.. 449

As noted in the preceding chapter, one of the two original major groups of arthropod-borne viruses, the Group B arboviruses, has become the genus Flavivirus of the family Fiaviviridae (the other, the Group A arboviruses, became the genus Alphavirus of the family Togavirtdae). Non-arthropod-borne viruses with physicochemical characteristics, gene order, and replication strategies similar to those of the arthropod-borne flaviviruses have also been placed in the family Flavwiridae, in the genus Pestivirus (which includes viruses of veterinary importance but no human pathogens) and another genus for human hepatitis C virus.

There are about 70 recognized member viruses in the genus Flavivirus; of these 13 cause disease in humans, varying from febrile illnesses, sometimes with rashes, to life-threatening hemorrhagic fevers, encephalitis, and hepatitis (see Table 26-2). Three of these, dengue (because of dengue hemorrhagic fever), yellow fever, and Japanese encephalitis viruses, rank among the most important viral pathogens of the developing world.

Hepatitic C virus was discovered in 1989 by a tour de force of molecular biology; even though its virion has neither been visualized nor cultivated, its complete nucleotide sequence has been determined, and it was allocated to the family Flnviviridae on the basis of the similarity of its genome organization to that of other members. Hepatitis C virus is now recognized to be quite as important as hepatitis A and B viruses and is today the most common cause of posttransfusion hepatitis.

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