Table 4.

Minimum infectious dose of selected waterborne pathogens

Organism	Minimum infectious dose
Ascaris	1–10
Campylobacter jejuni	∼500
Cryptosporidium	10–100
E. coli O157:H7	10–100
Entamoeba histolytica	10–100
E. coli	1–100 million
Giardia	10–100
Hepatitis A virus	1–10
Rotavirus	∼1
Salmonella spp.	10 000–10 million
Salmonella typhi	10
Shigella spp.	10–100
Vibrio cholerae	1000