Pneumonia is a condition, not a disease, with many different causes. It can be caused by a range of bacteria and viruses, as well as by fungi or by chemicals and dust particles entering the lungs:
http://www.nhs.uk/Con...nia/Pages/Causes.aspx
As will be seen from that link, the most common cause of pneumonia in adults is Streptococcus pneumoniae, also called 'pneumococcus.
Quote:
"Pneumococcus is spread through contact between people who are ill or who carry the bacteria in their throat. You can get pneumococcal pneumonia from respiratory droplets from the nose or mouth of an infected person. It is common for people, especially children, to carry the bacteria in their throats without being sick".
Source:
http://www.medicinene....asp?articlekey=60945
Chris