Mild dengue fever causes a high fever and flu-like symptoms. The severe form of dengue fever, also called dengue hemorrhagic fever, can cause serious bleeding, a sudden drop in blood pressure (shock) and death. Half a million patients are hospitalized each year, but most people recover after two to seven days. Some develop dengue hemorrhagic fever after the initial fever declines — a more severe form of the illness that can cause organ damage, severe bleeding, dehydration and even death.