Hospital-acquired pneumonia (HAP) or any pneumonia which is contracted by a patient in a hospital at least 48–72 hours after entry: Nosocomial respiratory infections are considered to be the second most common hospital infection (urinary tract infection is the most common) and it accounts for 15–20% of the total infections that are acquired from medical facilities.

Nosocomial respiratory infections are said to be the most common causes of death that are transmitted in intensive care units or infirmaries.