Herpes simplex viruses. Coloured transmission electron micrograph (TEM) of herpes simplex viruses (HSV, red and blue) budding from the surface of a cell (orange). Viruses at higher magnification are shown inset, bottom right. Viruses infect cells, hijack the cell's internal machinery to replicate themselves, then release hundreds of clones from the cell's surface to infect further cells. HSV causes watery blisters on the skin, mucous membranes and genitals.