| Adair County |
6 |
| Andrew County |
9 |
| Audrain County |
1 |
| Barry County |
5 |
| Barton County |
8 |
| Bates County |
23 |
| Benton County |
3 |
| Bollinger County |
1 |
| Boone County |
32 |
| Buchanan County |
4 |
| Butler County |
1 |
| Caldwell County |
9 |
| Callaway County |
13 |
| Camden County |
3 |
| Cape Girardeau County |
6 |
| Carroll County |
3 |
| Carter County |
1 |
| Cass County |
25 |
| Cedar County |
6 |
| Chariton County |
4 |
| Christian County |
8 |
| Clark County |
5 |
| Clay County |
19 |
| Clinton County |
10 |
| Cole County |
5 |
| Cooper County |
6 |
|
| Crawford County |
2 |
| Dade County |
8 |
| Dallas County |
14 |
| Daviess County |
11 |
| Dekalb County |
3 |
| Dent County |
1 |
| Dunklin County |
2 |
| Franklin County |
14 |
| Gasconade County |
4 |
| Gentry County |
6 |
| Greene County |
6 |
| Grundy County |
3 |
| Harrison County |
7 |
| Henry County |
8 |
| Hickory County |
5 |
| Holt County |
2 |
| Howard County |
3 |
| Iron County |
1 |
| Jackson County |
21 |
| Jasper County |
5 |
| Jefferson County |
16 |
| Johnson County |
20 |
| Laclede County |
7 |
| Lafayette County |
15 |
| Lawrence County |
6 |
| Lewis County |
5 |
|
| Lincoln County |
14 |
| Linn County |
7 |
| Livingston County |
8 |
| Macon County |
12 |
| Madison County |
1 |
| Maries County |
2 |
| Marion County |
3 |
| McDonald County |
1 |
| Mercer County |
1 |
| Miller County |
3 |
| Mississippi County |
1 |
| Moniteau County |
9 |
| Monroe County |
3 |
| Montgomery County |
2 |
| Morgan County |
10 |
| Newton County |
1 |
| Nodaway County |
17 |
| Pemiscot County |
1 |
| Perry County |
2 |
| Pettis County |
7 |
| Phelps County |
7 |
| Pike County |
2 |
| Platte County |
6 |
| Polk County |
9 |
| Pulaski County |
3 |
|
| Putnam County |
1 |
| Ralls County |
2 |
| Randolph County |
9 |
| Ray County |
12 |
| Saint Charles County |
6 |
| Saint Clair County |
3 |
| Saint Francois County |
8 |
| Saint Louis City |
1 |
| Saint Louis County |
12 |
| Sainte Genevieve County |
1 |
| Schuyler County |
1 |
| Scotland County |
3 |
| Scott County |
2 |
| Shannon County |
1 |
| Shelby County |
1 |
| Stoddard County |
16 |
| Stone County |
3 |
| Sullivan County |
4 |
| Taney County |
1 |
| Texas County |
4 |
| Vernon County |
13 |
| Warren County |
4 |
| Washington County |
3 |
| Wayne County |
1 |
| Webster County |
2 |
| Worth County |
1 |
| Wright County |
4 |
|
These county and county - equivalent data are based on tests of tissue samples from dead and diseased wild birds, provided by state health officials. Many of these data represent crows, which are especially sensitive to West Nile Virus (WNV). Note that the map includes all areas of positive (confirmed or probable) WNV results, but not necessarily all areas with submitted samples or no reports.
