Eighty percent of the world's illness is caused by fecal matter. A gram of feces can contain 10 million viruses, 1 million bacteria, 1,000 parasite cysts, and 100 worm eggs. Bacteria can be beneficial: the human body needs bacteria to function, and only 10 percent of cells in our body are actually human. Plenty are not. Small fecal particles can then contaminate water, food, cutlery, and shoes-and be ingested, drunk, or unwittingly eaten. One sanitation specialist has estimated that people who live in areas with inadequate sanitation ingest 10 grams of fecal matter every day.