Neonatal sepsis is a type of neonatal infection and specifically refers to the presence in a newborn baby of a bacterial blood stream infection (such as meningitis, pneumonia, pyelonephritis, or gastroenteritis) in the setting of fever. It is divided into two categories: early-onset sepsis (EOS) and late-onset sepsis (LOS). EOS refers to sepsis presenting in the first 3 days of life, and is usually caused by Group B Streptococci or Escherichia coli. It presents with pneumonia. LOS is the presentation of sepsis after 3 days, and is usually caused by Staphylococcus. It presents with meningitis. The treatment depends on the underlying etiology.