Transmission electron micrograph (TEM) of paracrystalline arrays of adenovirus particles (dark spheres) in an infected cell. A close-up of one of the arrays is shown at right. Each virus consists of an icosahedral protein coat (capsid) surrounding double stranded deoxyribonucleic acid (DNA), the virus' genetic material. Adenoviruses most commonly cause respiratory disease in humans, but can also cause genitourinary diseases and gastroenteritis. These viruses have also proved successful for use as vectors in gene therapy and DNA vaccination.