Cytomegalovirus is an important pathogen in all age groups inducing severe birth defects to a wide spectrum of disorders. Respiratory synctial viruses also cause lower respiratory infection in all age groups. They can cause serious infections in immunocompromised, elderly and infants. Enterovirus are the most common viral infectious agents in humans. Parechoviruses are associated with respiratory disease but may also cause mild gastroenteritis. Adenoviruses cause a variety of illnesses including respiratory infections, gastroenteritis, conjunctivitis and cystitis.