Page "Human pathogen" Paragraph 11

Transmission of pathogens occurs through many different routes, including airborne, direct or indirect contact, sexual contact, through blood, breast milk, or other body fluids, and through the fecal-oral route.

One of the primary pathways by which food or water become contaminated is from the release of untreated sewage into a drinking water supply or onto cropland, with the result that people who eat or drink contaminated sources become infected.

In developing countries most sewage is discharged into the environment or on cropland ; even in developed countries there are periodic system failures resulting in a sanitary sewer overflow.