Adenoviruses can cause a spectrum of respiratory disease as well as infection of the stomach and intestine (gastroenteritis), eyes (conjunctivitis), bladder (cystitis) and rash. Adenovirus respiratory diseases include a form of the common cold, pneumonia, croup, and bronchitis. Patients with compromised immune systems are especially susceptible to severe complications of adenovirus infection. Acute respiratory disease (ARD), a disorder first recognized among military recruits during World War II, can be caused by adenovirus infections under conditions of crowding and stress. Adenoviruses are transmitted by direct contact, fecal-oral transmission, and occasionally waterborne transmission. Some types of adenoviruses are capable of establishing persistent asymptomatic infections in the tonsils, adenoids, and intestines. Shedding of the virus can occur for months or years after the initial infection.