But now, experts know that the bacteria live in thick mucus called sputum in a person’s lower respiratory system—the lower throat and lungs.

The inherited ailment, from a single defective gene, clogs lungs with thick mucus, causing life-threatening infections.

This means the cells no longer produce the thick mucus.

Many of these symptoms occur when bacteria that normally inhabit the thick mucus grow out of control and cause pneumonia.

The whelk can also secrete a thick mucus that may or may not contain biotoxins to weaken the prey.