This negative-stained transmission electron micrograph (TEM) image depicted the ultrastructural details of an Orf virus, a member of the genus Parapoxvirus. Note the spiral arrangement of the external tubular ridges on the ovoid-shaped virus particle, or virion. The criss-cross pattern is an artefact caused by superimposition of images of top and bottom surfaces of the virion.

The orf virus is a pathogen common to sheep and goats, but can at times be transmitted to humans, in which case the virus is known as being “zoonotic”. When a human being becomes infected, the symptoms are mainly confined to the skin, and consist of “weeping” nodules manifesting upon the dorsum, or back of the hands, and which heal in approximately thirty-five days in a spontaneous fashion.

Photo credit: Cynthia Goldsmith

Source:CDC's Public Health Image Library Image #8434

Dieses Bild ist ein Werk der Centers for Disease Control and Prevention, einer dem Gesundheitsministerium der Vereinigten Staaten unterstellten Behörde, oder es wurde von einem Mitarbeiter dieser Behörde in Ausübung seiner dienstlichen Pflichten erstellt. Als ein Werk der US-amerikanischen Bundesregierung ist dieses Werk in den Vereinigten Staaten gemeinfrei.