Lung infection happens, I mean like tuberculosis. If somebody has tuberculosis and it goes into the air and we breathe that air, then tuberculosis can go into the lungs and enter through the lungs.
Some of the bugs as we breathe the air, go into our lungs and start causing pneumonia or infection. Some of the microbes/bugs which cause pneumonia are streptococcus, even Staphylococcus influenza or flu virus A and B legionella. Almost in 70% of the cases, pneumonia is caused by Streptococcus pneumonia.
As we get older, yes, we become more prone to pneumonia. Sometimes, we may not be in good health that makes us more prone to pneumonia or lung infections. Smoking also affects our defense mechanisms, even alcohol makes us more prone to pneumonia.
I will tell you if you keep lying, even a young person keeps lying in bed for several months, he or she will be at the very risk of dying either from pneumonia or from urine infection. That is why we need a very active lifestyle and breathing exercises which keep our lungs healthy.
We do have pneumonia vaccines and we are going to write a separate book on all the different vaccinations we need at different stages of life.