Are respiratory viruses involved in preseasonal symptoms or severity in Japanese cedar pollinosis?

BACKGROUND Respiratory virus infections are involved in asthma exacerbations. However, there are no reports of the relationship between respiratory virus infections and Japanese cedar pollinosis. OBJECTIVE We studied the relationship between respiratory viral infection and the appearance of preseasonal symptoms and the severity of seasonal symptoms in Japanese cedar pollinosis. METHODS In 36 patients with asthma and with no symptoms (PreAsyP) and 54 patients with asthma and with symptoms (PreSyP) before the cedar pollen shedding commenced (preseason), and 37 patients with mild-to-moderate severity (InMild/Mod) and 45 patients with severe to extreme severity (InSev/Ext) after cedar shedding commenced (in season), the occurrence of respiratory viruses and nasal smear cytology were examined. RESULTS In total, seven infections with respiratory viruses were detected among the subjects. Human rhinovirus (HRV) C infection was detected in one subject in each of the PreAsyP and PreSyP groups, and one HRVA infection occurred in the InMild/Mod group. In the InSev/Ext group, one HRVA, one HRVC, one respiratory syncytial virus, and one human metapneumovirus were detected. There was no significant difference in the rate of detection of viral infections between the PreAsyP and the PreSyP groups (p = 0.077), and between the InMild/Mod group and the InSev/Ext group (p = 0.24, Wilcoxon rank sum test). When cells types in nasal smears were identified and their abundance examined, the rate of neutrophilia in the subjects in the PreSyP group was 54%, which was statistically higher (p < 0.01) than the subjects in the PreAsyP group (25%). Interestingly, in the subjects in the InSev/Ext group, the proportion of eosinophils (40%) was larger (p < 0.05) than in the subjects in the InMild/Mod group (19%). CONCLUSION These results provided no evidence that respiratory virus infections contributed to preseasonal symptoms and severity in season of Japanese cedar pollinosis. Nasal neutrophilia was related to preseasonal symptoms, whereas nasal eosinophilia was related to severity of symptoms during the pollen season.