Pneumonia Causes: What Triggers It and How It Spreads

When your lungs fill with fluid or pus, it’s usually because of an infection called pneumonia, a lung infection that inflames the air sacs and can make breathing difficult. Also known as lung infection, it’s one of the most common serious respiratory illnesses worldwide and affects millions every year. It doesn’t just show up out of nowhere—it starts with something that gets into your lungs and your body can’t fight off quickly enough.

Most cases come from bacteria, tiny organisms like Streptococcus pneumoniae that live in the air and spread through coughs or close contact. But viruses, including flu, RSV, and even COVID-19, are just as common causes, especially during cold and flu season. Fungi and inhaling food or chemicals can also trigger it, but those are rarer. Your immune system usually keeps these invaders in check—but if you’re older, have asthma, smoke, or just got over a cold, your defenses drop and pneumonia moves in.

It’s not just about what causes it—it’s about who’s at risk. People with chronic diseases like diabetes or heart failure are more likely to get it. So are kids under 2 and adults over 65. Even healthy people can catch it after a bad flu or if they’re in a hospital, especially on a ventilator. And while pneumonia isn’t always contagious, the germs that cause it definitely are. You can pick them up from shaking hands, touching a doorknob, or being near someone who’s coughing.

What you’ll find in the posts below isn’t just a list of medical terms. It’s real, practical info on how infections spread, what makes them worse, and how treatments like antibiotics or antivirals actually work. You’ll see how pneumonia connects to other lung conditions, what medications help, and how your overall health plays a role. Whether you’re worried about a loved one, recovering yourself, or just trying to understand why you got sick, these posts give you the clear facts—no fluff, no jargon, just what matters.