Assessment of Future Scientific Needs for Live Variola Virus (1999) / Chapter Skim
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3 Clinical Features of Smallpox
3 Clinical Features of Smallpox
Pages 25-32
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From page 25... ...
Secretions from the mouth and nose, rather than scab material, are the most important source of human-to-human transmission. The initial infection in the oropharynx or respiratory tract produces neither symptoms nor local lesions, and patients are not infectious until an oropharyngeal enanthem appears at the end of the primary incubation period.
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From page 26... ...
A local skin lesion appears on the third or fourth day, with fever and constitutional symptoms beginning on the eighth day. The incubation period is typically 2 to 3 days shorter than in natural smallpox.
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From page 27... ...
Degeneration occurs simultaneously in several parts of the gland, leading to extensive necrosis. When healing occurs, the defect in the dermis fills with granulation tissue, which frequently shrinks, leaving localized facial pockmarks.
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From page 28... ...
Later, increasing vascularization takes on the appearance of granulation tissue, with numerous polymorphonuclear leukocytes in the demarcation zone beneath the necrotic epithelium. The lack of a homy, keratinized cell layer permits the lesions on the mucous membranes to ulcerate soon after their formation, releasing large amounts of highly infectious virus into the saliva.
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From page 29... ...
Certain T cells are cytotoxic and actively destroy cells exhibiting specific viral proteins composed of MHC products on their surface. During infection with a virus as complex as an orthopoxvirus, antibodies specific to many different viral proteins are generated.
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From page 30... ...
In children with immunological defects in cell-mediated immunity, vaccinia virus replicates without restriction, resulting in a continually progressive primary lesion, persistent viremia, and widespread secondary viral infection of many organs. In patients with thymic dysplasia and partially or completely intact immunoglobulin-synthesizing capacity (Nezelof's syndrome)
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From page 31... ...
Passive immunization, as a natural consequence of either transmission of antibodies from mother to progeny or the administration of antisera, is less effective in modifying the course of disease than active immunization involving live virus. Active immunity, whether elicited by vaccination or the disease, provokes the complete range of cell-mediated and humoral immune responses, whereas passive immunization provides only the antibodies present in the source of the sera.
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