When just one part of the lung or one lung is affected, the person can continue to breathe using the other lung while their body fights the infection.
Pneumonia is a serious infection that fills the lungs with liquid or pus and can make it difficult to breathe.
The Vatican has also said the infection affecting Pope Francis’s lungs is “polymicrobial”.
However having pneumonia can damage the lungs, and this can make a repeat infection more likely.
This means it’s usually very easy to see where pneumonia is affecting them, because the infection shows up as solid white mass on the scan.
