Frank Wallace, who is unemployed, displays a sign during a vigil in Philadelphia. The Philadelphia Unemployment Project and other organizations gathered to draw attention to federal unemployment benefits that are scheduled to expire.
Eggs of the parasite called the human whipworm, responsible for Trichuriasis, a disease that affects the large intestine and causes gastrointestinal problems. Drug companies are now trying to create parasites for treating inflammatory bowel disease.
Public Health Image Library/CDC