Inclusion Criteria for Covid-19 positive patients:  Clinically tested for SARS-CoV-2 (as completed by standard laboratory testing e.g. RT-PCR) with a positive result Clinical features in keeping with COVID-19 illness.  Inclusion criteria for Covid-19 negative patients:  Negative RT-PCR COVID-19 test Without any clinical features to suggest COVID-19 illness. No known or current features of respiratory infection, COPD, asthma, interstitial lung disease, other respiratory inflammatory conditions or lung cancer. Able to provide a breath sample (as based on clinical judgement).  Exclusion Criteria for Covid-19 positive and negative patients:  - Unable to provide a breath sample