The associations of upper respiratory tract infections with exacerbations of asthma

Abstract

A cohort of 9-11 year old children with wheeze and/or persistent cough, kept diary cards of upper and lower respiratory symptoms, treatment and twice daily peak expiratory flow (PEF) recordings from 1.3.89-7.5.90. New methods of virological diagnosis were developed: the polymerase chain reaction (PCR) was shown to be at least 3 times more sensitive than standard methods in the diagnosis of picornaviral infection. PCR was used to detect picornaviral, coronaviral and Mycoplasma and Chlamydia pneumoniae infections, as well as immunofluorescence, enzyme linked immunosorbent assays and cell culture with 5 cell lines to detect other respiratory viruses in 292 samples. Clinical data was computerised to define episodes of clinically significant symptoms or falls in PEF, and to analyse associations with viral infections. Viral infections (61% rhinoviral, 17% coronaviral) were detected in 80% of exacerbations of wheeze, 80% of those with a fall in PEF (median maximal fall 81 1/min, duration of 14 days), and 85% of those with cold symptoms, cough, wheeze and a fall in PEF. Atypical bacterial infection was not important. Time trend analysis revealed strong correlations between viral infections in the cohort of children and asthma admissions in the Region from which the cohort was drawn, for both adults (r=0.53, P&lt;0.01) and children (r=0.68, P&lt;0.0001). Analysis revealed that children diagnosed as asthmatic had more frequent upper respiratory infections, and more frequent and more severe lower respiratory infections, and more severe falls in PEF than those not diagnosed as asthmatic. Atopy alone was associated with more severe lower respiratory symptoms and falls in PEF. These results suggest a pivotal place for ICAM-1 in virus-induced allergic disease.</p