- (1981) – The “Morbidity and Mortality Weekly Report” of the Centers for Disease Control and Prevention reports 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.
- (1862) – Swedish ophthalmologist and optician Allvar Gullstrand is born. He applied the methods of physical mathematics to the study of optical images and of the refraction of light in the eye. For this work, he received the Nobel Prize in Physiology or Medicine in 1911.
- World Environment Day