Table 2.

Occurrence of Escherichia coli in drinking water for humans

Source of water	Total number of samples tested	Range of Escherichia coli counts per 100 ml	Mean Escherichia coli count per 100 ml
Protected spring	9	< 30–4.2 × 103	493.3
Unprotected spring	13	4.5 × 103–4.35 × 107	13,017.7
Protected open wells	2	< 30–5 × 103	2515
Unprotected open wells	4	5.5 × 103–9.8 × 103	7650
Stream	2	1.15 × 104–1.18 × 104	11,650