| Risk Factor | Attributable risk |
| Consumption of undercooked or raw pork products | ++++ |
| Exposure to untreated surface water | ++ |
| Minority infants (United States) | + |
| Blood transfusion | + |
| Derangements of iron-metabolism (cirrhosis, hemochromatosis, aplastic anemia, thalassemia, iron-overload) | ++ |
| Other conditions (malignancy, diabetes, malnutrition, gastrointestinal illness) | + |
