Diphtheria is a highly contagious disease that is contracted by inhaling bacteria from an infected person. The disease is still common in 87 countries, with some strains continuing to circulate in parts of the U.S. Travel destinations where diphtheria is found include certain parts of Africa, Europe, Central America, the Caribbean, the former Soviet Republics, and Asia. Symptoms begin very much like a common cold, usually two to five days after transmission, but can progress quickly. In some cases, a membrane grows and covers the throat, which can block the airway. The infection can lead to heart failure and paralysis, and, if enough toxin from the membrane is absorbed into the bloodstream, coma or even death in as little as a week.