However, virions released naturally from infected cells acquire an additional envelope, which is easily lost during manipulation ( Fig. Virions extracted artificially from infected cells are infectious and are generally used in studies on poxviruses. Parapoxviruses are narrower (160 nm) and have one long tubule that winds around the virion in electron micrographs, superimposition of the top and bottom surfaces gives a characteristic criss-cross appearance ( Fig 69-3). Orthopoxviruses are approximately 240 nm by 300 nm, with short surface tubules 10 nm wide. Poxvirus virions are large and brick shaped. Respiratory complications were seen in about 12 percent of unvaccinated patients. Detailed examination of more than 300 cases in Zaire showed an overall mortality of 10 percent, reaching 15 to 20 percent in unvaccinated children. A febrile prodrome precedes the development of a vesicular or pustular rash, typically centrifugal in distribution. However, routine use of smallpox vaccine has been discontinued, and any future use of recombinant vaccinia virus vaccines will involve attenuated strains, thus reducing the chances of complications.Īlthough human monkeypox is rare and geographically localized, it is a serious generalized infection, which clinically resembles mild smallpox ( Figs. Smallpox vaccination has been associated with serious complications. Infection in immunocompromised or eczematous individuals is more severe and usually results in generalized illness, and in cowpox has caused deaths. Rare encephalitic complications of cowpox have been reported, and erythema multiforme is a complication of parapox infections. Human cowpox is very painful, particularly in young children, usually causes pyrexia and marked lymphadenopathy patients often require hospitalization. Parapox and molluscum infections are relatively painless and cause very little constitutional disturbance. Numbers indicate progression of infection. Localized and generalized poxvirus infections.
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