 The hepatitis research was instrumental in determining a virus is responsible for the disease and that it is transmitted through human filth , serum and drinking water . 
 The hepatitis research was instrumental in determining a virus <a href='drop_aux' title='1'><mark>is</mark></a>responsible for the disease and that it is transmitted through human filth , serum and drinking water . 
Da hepatitis research was instrumental in determining a virus responsible for tdadisease and that it is transmitted through human filth , serum and drinkin water .