Adenoviruses can affect people of all ages, but are more likely to cause severe illness in children than in adults. In infants and young children, adenoviruses most commonly cause respiratory illnesses, such as croup, bronchitis, and pneumonia. In older children and adults, adenoviruses can cause a variety of illnesses ranging from mild upper respiratory infections to more serious illnesses such as urinary tract infections, conjunctivitis (pink eye), gastroenteritis (stomach flu), and even inflammation of the heart (myocarditis).
Adenoviruses are also a common cause of respiratory illness in soldiers, especially those in close living quarters such as dormitories or barracks. In rare cases, adenoviruses can cause more serious illnesses such as meningitis, encephalitis, and hepatitis.
In addition to causing respiratory and other illnesses, adenoviruses can also cause conjunctivitis, a common eye infection that is usually spread through contact with contaminated surfaces. Conjunctivitis can affect people of all ages, but is most common in young children.