Droughts. The immediate emergency effects of a drought are subtle when compared to those brought on by natural disasters such as tornadoes or hurricanes. In a region that has been severely affected by a drought, mortality may increase sharply due to protein malnutrition (kwashiorkor) or calorie malnutrition (marasmus). Certain vitamin deficiencies, such as a lack of Vitamin A, can lead to specific consequences such as xerpohthalmia and child blindness. Long standing malnutrition can easily lead to increased rates of disease and mortality, and limit the general population's functionality. In some cases, mass moveme nts of people spurred by long-standing drought and food shortages can lead to over-crowding and collectively poor hygiene. Over-crowding can easily lead to an increase in the transmission rates of communicable diseases such as tuberculosis or gastro- intestinal infections.