Herpes simplex virus infection. Coloured scanning electron micrograph (SEM) of fibroblast cells infected by the herpes simplex virus (HSV2). Fibroblast cells secrete fibres in connective tissue, they are normally long and star-shaped. The HSV2 (not seen) infected the cells 24 hours earlier, causing them to shrink and become rounded. HSV2 is a DNA-containing virus that causes genital herpes, an important sexually- transmitted disease. Magnification: x400 at 6x7cm size.