<prompt> A patient has undergone a renal transplantation 2 months back and now presented with difficulty in breathing. X-ray showed bilateral diffuse interstitial pneumonia. The probable etiologic agent would be :CMVHistoplasmaCandidaPneumocystis carinii  <response>: Cytomegalovirus CMV is the largest virus in the herpes family. It is transmitted transplacentally from a latent mother to foetus. Postnatal infections are usually acquired by means of sexual intercourse, blood transmission and organ transplantation , clinical disease resembles infectious mononucleosis . It may cause hepatitis and pneumonitis. For treatment Ganciclovir is the drug of choice.Ref : textbook of microbiology, C P Baveja, 5th edition , Pg no:446 