Legionnaires' disease showed that Legionnaires' disease was responsible and the immediate epidemiological investigation traced the source of the infection to the air-conditioning cooling tower on the roof of Stafford District Hospital. In March 1999, a large outbreak in the Netherlands occurred during the Westfriese Flora flower exhibition in Bovenkarspel; 318 people became ill and at least 32 people died. This was the second-deadliest outbreak since the 1976 outbreak and possibly the deadliest, as several people were buried before Legionnaires' disease had been diagnosed. The world's largest outbreak of Legionnaires' disease happened in July 2001 with people appearing at the hospital on July
Pneumonia increased risk of getting pneumococcal disease. The pneumococcal vaccine has been shown to reduce the risk of community acquired pneumonia in people with chronic obstructive pulmonary disease (COPD), but does not reduce mortality or the risk of hospitalization for people with this condition. People with COPD are suggested to have a pneumococcal vaccination. Other vaccines for which there is support for a protective effect against pneumonia include pertussis, varicella, and measles. When influenza outbreaks occur, medications such as amantadine or rimantadine may help prevent the condition; however are associated with side effects. Zanamivir or oseltamivir decrease the chance that people