| Summary: | Chronic obstructive pulmonary disease (COPD) is an inflammatory condition of the lung caused by an abnormal response to particles and noxious gases, primarily cigarette smoke. Patients suffer daily symptoms and can have episodes of worsening symptoms termed acute exacerbations. Exacerbations are associated with impaired quality of life, faster lung function decline, higher mortality and increased risk of hospitalisation. The aetiology of COPD exacerbations is controversial; however respiratory viral and bacterial infections are an important feature of exacerbations. This study utilised real-time qPCR to measure prevalence and load of human rhinovirus (HRV) in stable COPD and during the time-course of naturally occurring exacerbations and their recovery. HRV was assessed in association with upper respiratory tract (URT) symptoms namely cold symptoms and sore throats, secondary bacterial infection, patient reported outcomes and exacerbation frequency. Additionally, respiratory syncytial virus (RSV) was semi-quantitatively examined in stable COPD and at exacerbation. The original contribution of this work to the field is that HRV prevalence and load are highest at exacerbation presentation and decrease during recovery. HRV load is higher in the presence of URT symptoms compared to the load without, and the load remains higher for longer with both symptoms compared to only one. This study described novel evidence for the development of secondary bacterial infection after HRV infection in natural exacerbations, and demonstrated that HRV infection is associated with patient reported outcomes. Patients with HRV had higher exacerbation frequencies compared to those without HRV. RSV prevalence did not change significantly between stable COPD and exacerbation. The findings from this thesis have important implications in terms of exacerbation therapy. The evidence provided may allow appropriate targeting of therapeutic interventions therefore reducing exacerbation severity and frequency. These findings emphasise the importance of rapid development of therapeutic targets for the prevention and treatment of HRV infection in COPD patients.
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