Influenza (the flu) is a very contagious infection caused by flu viruses. The flu can cause a mild to severe infection in your nose, sinuses, throat and lungs. Every year, severe cases of the flu result in many hospitalizations and deaths.
Although flu infections can occur at any time throughout the year, the risk increases in the fall and peaks in the winter.
Pneumonia (nu-MO-ne-ah) is swelling (inflammation) of one or both lungs that is usually caused by an infection. Pneumonia can be life-threatening. It’s a leading cause of death and hospitalization in seniors and in people with chronic diseases.
Many different germs can cause pneumonia, including bacteria, viruses, and fungi. When you breathe in these germs, they can settle in the alveoli (air sacs) in your lungs and cause an infection.
When your lungs become infected, the alveoli fill with pus and mucus, blocking oxygen from getting into your bloodstream. As you work harder to breathe in more oxygen, you can feel short of breath. The swelling and infection also cause many other pneumonia symptoms like cough, fever and chest pain.