tailieunhanh - 16th Edition Harrison’s Principles of Internal Medicine_2

Tham khảo sách '16th edition harrison’s principles of internal medicine_2', y tế - sức khoẻ, y học thường thức phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | inn infections caused by arthropod- and rodent-borne viruses mu Clarence J. Peters Some viruses are transmitted in nature without regard to humans and only incidentally infect and produce disease in humans in addition a few agents are regularly spread among humans by arthropods. Most of these viruses either are maintained by arthropods or chronically infect rodents. Obviously the mode of transmission is not a rational basis for taxonomic classification. Indeed zoonotic viruses from at least seven virus families act as significant human pathogens Table 180-1 . The virus families differ fundamentally from one another in terms of morphology replication mechanisms and genetics. Information on a virus s membership in a family or genus is enlightening with regard to maintenance strategies sensitivity to antivirals and some aspects of pathogenesis but does not necessarily predict which clinical syndromes if any the virus will cause in humans. FAMILIES OF ARTHROPOD- AND RODENT-BORNE VIRUSES Table 180-1 The Arenaviridae The Arenaviridae are spherical 110- to 130-nm particles that bud from the cell s plasma membrane and utilize ambisense RNA genomes with two segments for replication. There are two main phylogenetic branches of Arenaviridae the Old World viruses such as Lassa fever and lymphocytic choriomeningitis LCM viruses and the NewWorld viruses including those causing the South American hemorrhagic fevers HFs . Arenaviruses persist in nature by chronically infecting rodents with a striking one-vứus-one-rodent species relationship. These rodent infections result in long-term virus excretion and perhaps in lifelong viremia vertical infection is common with some arenaviruses. Humans become infected through the inhalation of aerosols containing arenaviruses which are then deposited in the terminal air passages and probably also through close contact with rodents and their excreta which results in the contamination of mucous membranes or breaks in the skin. The Bunyaviridae