Pneumonia exposure to cigarettes or air pollution, malnutrition, and poverty. The use of acid-suppressing medications — such as proton-pump inhibitors or H2 blockers — is associated with an increased risk of pneumonia. Approximately 10% of people who require mechanical ventilation develop ventilator associated pneumonia, and people with gastric feeding tube have an increased risk of developing of aspiration pneumonia. For people with specific variants of FER gene, the risk of death is reduced in sepsis caused by pneumonia. However, for those with TLR6 variants, the risk of getting Legionnaires' disease is increased. Bacteria are the most-common cause of community-acquired pneumonia (CAP),
1976 Philadelphia Legionnaires' disease outbreak 25 had died. Both the first week and later, there were 149 Legionnaires who became sick and 33 other persons associated with the hotel or in the area who also became sick. Of these total of 182 cases, 29 persons died. The U.S. Centers for Disease Control and Prevention mounted an unprecedented investigation and, by September, the focus had shifted from outside causes, such as a disease carrier, to the hotel environment itself. In January 1977, the "Legionella" bacterium was finally identified and isolated and was found to be breeding in the cooling tower of the hotel’s air conditioning system,