Hepatitis A virus. Colored transmission electron micrograph (TEM) of a cluster of Hepatitis A virus particles. Here, viruses appear circular in shape (red), approximately 25-30 nanometers in diameter. These small RNA viruses are similar in structure to the Picornavirus group (which includes enterovirus and rhinovirus). Hepatitis A virus is the agent which causes infectious hepatitis. The virus attacks the liver producing liver inflammation and fever, followed by jaundice. The virus is excreted in the feces. Hepatitis A is transmitted by water or food contaminated with infected feces. The disease is more prevalent in warm countries with poor standards of hygiene.