Also called pneumococcus, this pathogen is the most common perpetrator of community-acquired pneumonia, which is pneumonia that people get outside hospitals and nursing homes.

Mrs. Clinton’s pneumonia affects her right lung’s middle lobe, according to Dr. Bardack, a location that suggests that it was caused by bacteria, commonly pneumococcus.

If you’re 65 or older, have a chronic illness or smoke, get vaccinated against pneumococcus.