Smallpox B03.x0

Highly contagious, severe, often lethal viral disease. 1979 Eradication of smallpox announced by the WHO. Suspicion of the disease is notifiable. In the context of bioterrorism, the smallpox viruses have become topical again.

Variola-verus virus (= Paschen's elementary corpuscle). DNA-containing cuboid virus of the Pox group. The natural host is man.

• Size: 200-400 nm, thus also visible under a very good light microscope.
• Shape: rectangular to oval.
• Envelope: extracellular with two, intracellular with one envelope.
• The linear, double-stranded genome consists of 130-300,000 base pairs (BP) whose ends are connected by covalent bonds. Both ends show an "inverted terminal repeat" (ITR) structure, which is about 10,000 BP long. It codes on both strands for about 200 proteins, with short, non-coded sequences between the reading frames. The genes of the early and late replication phase are arranged in groups.
• The virus is taken up by fusion of the outer virus envelope with the cell membrane or by endocytosis after binding on the surface. The capsid is later freely present in the cytoplasm. An entrained protein immediately ensures that DNA and RNA synthesis is switched off, which also brings the cell's own protein synthesis to a standstill. Transcription of the "early" genes still occurs in the capsid, which is mediated by enzymes carried along. This happens in microscopically visible "virus factories", called Guarnierian EK. About half of the genes are transcribed, then a CAP group is added to the 5' end and the 3' end is polyadenylated. Two resulting proteins are important for the induction of intermediate and "late" early genes.
• S. and pox viruses.

Incubation period: 7-17 days.

Initial stage: Over 3 days fever 40-41 °C, tachycardia, vomiting, headache and aching limbs. Initial exanthema: Small, slightly raised, red spots, beginning on the face and arms, spreading over the whole body. Edema of the eyelids. Temperature drop after about 3 days.

Eruption stage: On the 5th day papular transformation of the spots, formation of clear vesicles, which become purulent on about the 8th day. Formation of lentil to pea-sized, multi-chambered, centrally dented pustules surrounded by a dark red courtyard. Monomorphic image within a dermatome, different stages of development in different dermatomes. Suppuration stage: temperature rise, delirious state, swelling of lymph nodes, hepatosplenomegaly.

Desiccation stage: Around day 12: drying of pustules, thick crusts. Formation of key-shaped indented scars, hyperpigmented scars in coloured people and hyperpigmented scars in whites.

After inoculation: Weaker course. Eruption of extensive ecchymoses instead of vesicles possible.

1. Fölster-Holst R (2018) Further viral diseases in dermatology. In: G. Plewig et al.(Hrsg) Braun-Falc0`s Dermatoloogy, Venerology and Allergology, Springer Reference Medicine p.127-128