TABLE 1—
Environmental Independent Variables That May Influence the Timing and Magnitude of Childhood Gastrointestinal Illness Incidence: Marshfield Epidemiologic Study Area, Central and Northern Wisconsin, 1991–2010
| Independent Variable | Aggregation Period (Weekly) | Source | No. Stations |
| Precipitation, cm | Sum | GHCN, USGS | 15 |
| Stream discharge change, % | Change (week0 – week-1)a | USGS | 3 |
| Average temperature, °C | Average | GHCN | 8 |
| Precipitation (cm) × average temperature (°C) | Not applicable | GHCN | 8 |
Note. GHCN = Global Historical Climatology Network (US National Climatic Data Center); USGS = US Geologic Survey.
a
Week0 refers to the current week and week-1 to the previous week.