Yellow fever was first described as a disease entity in the 17th century. Its etiology and mode of transmission were the subject of intense interest and speculation during the 250 years which followed. Without specific tests and clear case definitions, yellow fever was clinically confused with other infections, including malaria, typhoid, typhus, leptospirosis, and other “bilious fevers”. Until the early 19th century, the disease was widely thought to be caused by airborne miasmas. One of America’s most prominent physicians, Dr. Benjamin Rush, proclaimed that the epidemic which struck Philadelphia in 1793 was due to atmospheric poison arising from a pile of decomposing coffee on a wharf.