William Henry Harrison dies of pneumonia becoming the first President of the United States to die in office and the one with the shortest term served.

American Civil War: Stonewall Jackson is wounded by friendly fire while returning to camp after reconnoitering during the Battle of Chancellorsville. He succumbs to pneumonia eight days later.

The Morbidity and Mortality Weekly Report of the Centers for Disease Control and Prevention report that five people in Los Angeles, California have a rare form of pneumonia seen only in patients with weakened immune systems, in what turns out to be the first recognized cases of AIDS.