Incidence of cold episodes
| Episodes n (%) | Incidence colds·subject-yr−1 | |
| Total | 211 | 1.41 |
| Centre# | ||
| Boston, MA | 39 (18.5) | 1.30 |
| Denver, CO | 31 (14.7) | 1.48 |
| Madison, WI | 50 (23.7) | 1.85 |
| San Diego, CA | 16 (7.6) | 1.13 |
| San Francisco, CA | 28 (13.3) | 1.47 |
| Saint Louis, MO | 23 (10.9) | 1.40 |
| Winston-Salem, NC | 24 (11.4) | 1.11 |
| Season | ||
| November–February | 93 (44.1) | 2.05 |
| March–June | 61 (28.9) | 1.15 |
| July–October | 57 (27.0) | 1.12 |
#: all USA.