The presence of which organism indicates a higher risk of waterborne diseases?

The presence of E. coli in water is a significant indicator of waterborne diseases because it is a specific type of coliform bacteria that originates in the intestines of warm-blooded animals. Its detection in water suggests fecal contamination, which can lead to the presence of other harmful pathogens that cause diseases. E. coli itself includes strains that can cause serious illnesses, especially gastrointestinal diseases, which underscores the public health risk it represents in contaminated water sources.

While the coliform group includes various types of bacteria, not all coliform bacteria are harmful. Therefore, the broader category indicates potential contamination but does not necessarily pinpoint the specific risk level associated with E. coli. Iron bacteria and Giardia lamblia, though they are also indicators of water quality issues, represent different concerns; iron bacteria generally indicate aesthetic problems in water quality, while Giardia is a protozoan parasite associated with specific gastrointestinal illnesses but is not a direct fecal indicator like E. coli.