Adenoviruses cause a wide variety of diseases, which may occur singly or currently. The most important are infections of the upper (sometimes lower) respiratory tracts, the eyes, and the intestinal tract.Adenoviruses are nonenveloped, 70 - 90 nm in size, and icosahedral. Their morphogenesis occurs in the cell nucleus, where they also aggregate to form large crystals. Their genome is a linear, double - stranded DNA. They mainly infect cells of the epithelium in the eyes, the pharynx, the respiratory and the intestinal tract. After an incubation period of 5-10 days different symptoms can occur (see table bellow). Humans are the source of infection. Susceptibility is the rule. Generalized contamination of the population begins so early in the childhood that Adenovirus infections play more a significant role in children than in adults. About 5% of all common colds at infants under 5 years might be caused by Adenoviruses and they are the second most frequent diarrhea pathogen after rotaviruses. Transmission of respiratory adenoviruses is primarily by droplet infection, but also as smear infections since the virus is also excreted in stool. Eye infections can be contracted from bathing water or, in the case of Adenovirus type 8 in particular, iatrogenically from insufficiently sterilized ophthalmological instruments. The enteral infections are also transmitted by the fecal-oral route, mainly by contact rather than in water or food.