Diseases Responsible pathogen Route of exposure Mode of transmission Cholera Vibrio cholerae bacteria gastro-intestinal often waterborne Botulism Clostridium botulinum bacteria gastro-intestinal food/water borne; can grow in food Typhoid Salmonella typhi bacteria gastro-intestinal water/food borne Hepatitis A Hepatitis A virus gastro-intestinal water/food borne Dysentery Shigella dysenteriae bacteria or Entamoeba histolytica amoeba gastro-intestinal food/water Cryptosporidiosis Cryptosporidium parvum protozoa gastro-intestinal waterborne; resists chlorine Polio polioviruses gastro-intestinal exposure to untreated sewage; may also be waterborne Giardia Giardia lamblia protozoa gastro-intestinal waterborne