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Viral Hemorrhagic Fevers: a Comparative Appraisal, Page 1 of 2
< Previous page Next page > /docserver/preview/fulltext/10.1128/9781555815981/9781555814250_Chap09-1.gif /docserver/preview/fulltext/10.1128/9781555815981/9781555814250_Chap09-2.gifAbstract:
This chapter provides a general survey of viral hemorrhagic fever (VHF), comparing individual diseases to each other and to other types of human illness. The HF viruses belong to four different families, the Arenaviridae, Bunyaviridae, Filoviridae, and Flaviviridae. The various types of VHF have presumably occurred for millennia, whenever humans have come into contact with reservoir animals or been bitten by infected arthropods. The transmission of a virus from animals to humans can occur through direct physical contact, exposure to virus containing excretions, or the bite of an infected mosquito or tick. Lassa fever, among other things, is characterized by uncontrolled viral replication, in which the circulating viral titer correlates with the likelihood of death. The circulation of more than one serotype in the same geographic region sets the stage for the occurrence of secondary infections, in which nonneutralizing antibodies can enhance virus uptake into cells, causing intense inflammation and increased vascular permeability. At present, the best-understood form of VHF is the fulminant illness caused by Ebola Zaire virus, which displays all the classic features of the HF syndrome. The signs and symptoms of VHF resemble those of a wide range of infectious diseases, so a specific diagnosis can be made only by means of specialized laboratory tests that directly identify the pathogen. Considerable progress has been made in developing experimental vaccines for a number of types of VHF, based on a variety of platforms.