Common cold

The common cold was a typical disease until the 26th century, when it was eradicated completely. However, it was reintroduced 500 years later by Fry's sneezing, causing the whole of Manhattan to be covered in saran wrap. The previously common disease is a threat to 31st Century society as the humans no longer have antibodies to fight off the disease.

Trivia

 * In the comic, which exists outside the canon of the episodes, the reintroduced common cold removed the infected people's inhibitions and when the infection passed, mucus based life forms were produced.