Cholera, a disease that is assuming serious proportions in hurricane-ravaged Haiti. Cholera strikes so fast it is sometimes called the lightening disease. Without rehydration therapy, or antibiotics for severe cases, cholera can kill in a matter of hours. The disease causes acute diarrhea that can lead to severe dehydration. Blood group O individuals have a greater risk of infection with cholera and develop the most severe and life threatening forms of this illness.