Though pneumonia is often thought of as a single illness, it actually comes in many different forms. While each type can cause the dangerous inflammation in your lungs—the result of an infection that leads to fluid or pus collecting in the lungs—the specific type of pneumonia can determine risk of severity, symptoms, and even treatment options.

Another thing that the specific type of pneumonia can shed light on: whether or not it’s contagious. (Yes, you heard that right: some forms of pneumonia are indeed able to be passed between people). To get more information on those types—and what you need to know about how they present and how to avoid them—we tapped some infectious disease experts. Here’s what you need to know about the contagious forms of pneumonia.  To read the full story.