Adenovirus is a group of viruses that can cause a range of illnesses in humans, including respiratory infections, conjunctivitis, and gastroenteritis. These viruses are common and can spread through respiratory droplets, direct contact, or contaminated surfaces. Symptoms often resemble those of the common cold or flu. Most people recover from adenovirus infections without treatment, but they can be more severe in infants, the elderly, or those with weakened immune systems. Vaccines are available for some types of adenovirus, particularly for military personnel, but there is no specific antiviral treatment for general infections.