what is the cause of pneumonia
Thanks for your question.
Pneumonia, which is an infection of the lungs, can be caused by many things. The most common cause is from bacteria, such as pneumococcus. There is a vaccine that can be used to help lower the risk for having bad pneumococcal infections. There are many other bacteria that can also cause pneumonias.
Tuberculosis is also a bacteria that can cause a pneumonia, but unlike pneumococcus in which you get sick with high fevers, chills and a cough over a few days, tuberculosis can creap up on you and cause a prolonged illness with cough, bloody sputum, weight loss, and sweats.
Viral infections, like flu can also cause pneumonia.
In people with HIV, especially with low CD4 counts, pneumonias can be caused by the common infections and also some opportunistic infections. Pneumocystis jiroveci (PCP) is very common. Other infections caused by fungi are Cryptococcus or histoplasmosis or coccidiomycosis (depending on where you live).
So there is no one simple cause of pneumonia. X-rays, CT scans and cultures of the blood and sputum can help make a diagnosis. Also getting your CD4 count up with meds can make you less at risk for pneumonia. and taking preventive medicine like bactrim if your counts are low can prevent PCP and other pneumonias (like bacterial pneumonias and toxoplasmosis).
Also, very important, if you smoke you are at higher risk for pneumonia since the normal protective lining of your airways can be damaged.