Hepatitis E virus (HEV), the causative agent of hepatitis E, is endemic in many developing countries. Hepatitis is an important public health disease in many developing countries on almost all continents including Asia, Africa and Mexico. Sporadic cases of acute hepatitis E have also been reported in many industrialized countries including the United States. The disease is primarily transmitted by fecal-oral route through contaminated water. The overall mortality rate is generally low (1%), but it can be as high as 20-25% in pregnant women, which is the most dangerous aspect of hepatitis E. So an efficient diagnostic and characterization system must be there to counter this public health problem. This book has molecular diagnostic and characterization system and basis for DNA vaccine development for hepatitis E.