Incubation Periods of Experimental Rhinovirus Infection and Illness

Eleven young adults with experimental rhinovirus infection (cases) and six noninfected saline-challenged young adults (controls) underwent nasal washings and symptom evaluations at 2-hour intervals for 24 hours after intranasal challenge. The mean and median periods to the first recovery of virus were 11.3 hours and 10 hours, respectively. Geometric mean rhinovirus titers in cases reached 10(0.2) log10 TCID50 (50% tissue culture infective dose)/0.1 mL at 10 hours and rose to 10(1.0) log10 TCID50/0.1 mL at 18 hours. Nine (82%) of 11 cases and one (16.7%) of six controls had colds. Mean total symptom scores for cases became significantly higher than those for controls at 16 hours. Sore or scratchy throat appeared between 10 and 12 hours in cases, but nasal obstruction and rhinorrhea first appeared at 2 hours, thus suggesting some nasal irritation from the viral inoculum pool. The incubation period of experimental rhinovirus infection is similar to that in cell culture. Nasal and pharyngeal symptoms began early in infection.