Comparison of asymptomatic and symptomatic rhinovirus infections in university students: incidence, species diversity, and viral load

Abstract

Human rhinovirus (HRV) infections are common but poorly characterized in university students. Thus, we characterized asymptomatic and symptomatic HRV infections by incidence, species diversity, and viral load of 502 university students during September and October of 2010 and 2011 from nasal swabs and electronically submitted symptom questionnaires. We tested all symptomatic students and randomly sampled participants who remained asymptomatic (n=25/week, over 8 weeks each study year) on a weekly basis by real-time PCR and sequenced HRV positives. HRV was identified in 33/400 (8.3%) and 85/92 (92.4%) of the asymptomatic and symptomatic students, respectively. We identified a higher than previously reported rate of HRV-B in both groups, although the distribution of HRV species was similar (P=0.37). Asymptomatic viral load averaged 1.2 log10 copies/mL lower than symptomatic HRV (P<0.001). In conclusion, asymptomatic HRV activity preceded peak symptomatic activity in September and October and was associated with lower viral load.

Keywords: Asymptomatic; Quantitative PCR; Rhinovirus; Species diversity; Viral load.

Fig. 1

Flow charts of study design during the McFlu2 COLD3 Prevention Trial, Hamilton, ON, Canada; weeks 36–43 2010 and weeks 36–43 2011.

Fig. 2

Weekly positivity rate of asymptomatic and symptomatic HRV in weeks 36–43 in 2010 and 2011. The percent positivity of HRV infections by week in 2010 (a) and 2011 (b) in university students. The percentage of positive asymptomatic HRV each week is determined by the number of HRVs identified in the 10% weekly random sampling (n = 25/week in 2010 and n = 25/week in 2011). The percentage of positive symptomatic HRV was determined by the number of positive HRV identified in the student population each week (n = 250/week in 2010 and n = 252/week in 2011).

Fig. 3

Box and whiskers plot of HRV viral loads (log₁₀ copies/mL) in asymptomatic (n = 33) and symptomatic (n = 85) university students. The solid line represents the median; the bottom and top of the box represent 25th and 75th percentiles, and the whiskers represent the minimum and maximum data points, respectively. Mean difference in viral load was 1.2 log₁₀ copies/mL (95% CI 0.59–1.72; P < 0.001).