Acute human immunodeficiency virus infection in a breast-fed infant in New York City.

Acute human immunodeficiency virus (HIV) infection in a breast-fed infant is a rare diagnosis in developed countries. We present a six-month old girl with postnatally acquired HIV infection complicated by Pneumocystis jéroveci pneumonia, cytomegalovirus pneumonitis and encephalopathy. Her mother had tested negative for HIV during pregnancy. Children infected by mothers during an acute seroconversion may have more rapid disease progression.