Smallpox viruses. Coloured transmission electron micrograph (TEM) of variola viruses, the cause of smallpox. The virus consists of genetic material (pink), DNA (deoxyribonucleic acid), enclosed by a protein capsid (coat, orange). Variola is the most virulent member of the orthopoxvirus group. It is specific to humans, having no other animal hosts. Infection with variola causes a high temperature and skin spots that develop into scarring pustules. It is transmitted by respiratory droplets or by the pus. Smallpox was eradicated in the 1970's by a global vaccination programme. However, isolated cultures of the virus are still kept in laboratories for research purposes. Magnification: x63000 when printed 10 cm wide. | |
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