By Karl Maramorosch
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Y. Acad. Sci. 753:1–412. De Quadros, C. , Hersch, B. , Olive, J. , Andrus, J. , da Silveira, C. , and Carraasco, P. A. (1997). Eradication of wild poliovirus from the Americas: Acute flaccid paralysis surveillance, 1988–1995. J. Infect. Dis. 175(S1): S37–S42. , and Blondel, B. (1997). Persistent poliovirus infection in mouse motoneurons. Journal of Virology 71:1621–1628. Detjen, B. , and Wimmer, E. (1978). Poliovirus single-stranded RNA and doublestranded RNA: Differential infectivity in enucleate cells.
Persistent poliovirus infections have not been reported by other investigators working with mouse models so this may represent an atypical biological variant. To date, the weight of evidence suggests that poliovirus does not cause persistent infections in immunocompetent humans or nonhuman primates. X. ERADICATION In 1988, the World Health Organization announced a goal to eradicate wild polioviruses. This initiative was founded on several biological parameters: (1) humans are the only known natural host for polioviruses; (2) poliovirus causes self-limited acute infections and can only perpetuate itself by infecting new susceptible hosts with a generation time of about 10 days; (3) if the number or density of susceptible hosts falls below a critical level, poliovirus fades away; and (4) OPV immunization reduces the ability of vaccinated subjects to act as links in the chain of transmission.
Under these circumstances, poliovirus would ‘‘fade out’’ during the winter even in the presence of considerable numbers of unvaccinated susceptible children. By contrast, there is very little seasonality in tropical climates (Nathanson and Martin, 1979). (2) In contrast to injected IPV, OPV must infect a vaccinated person in order to produce an immune response. When a group of seronegative susceptible children are fed OPV, most (but not all) will be Confirmed polio cases 8000 6000 4000 Nigeria stops OPV 1 year 2000 0 1998 2000 2002 Year 2004 2006 FIGURE 9 Global incidence of confirmed cases of paralytic poliomyelitis, 1997–2006, cumulated for Africa, Southeast Asia, and Eastern Mediterranean regions [after WHO (2007), with permission].
Advances in Virus Research, Volume 71 by Karl Maramorosch