Infection contributes to developing cardiac arrhythmias such as atrial fibrillation (AF), which causes over 25% of ischaemic stroke. We analysed a hospital coding database of patients hospitalised with COVID-19 +/-AF or a lower respiratory tract infection (LRTI) +/-AF, to compare the incidence of first-diagnosed or ‘new’ AF (nAF) between COVID-19 and LRTI, as well as risk-factors associated with developing nAF during COVID-19. 2243 LRTI and 488 COVID-19 patients were included. nAF was diagnosed in significantly more COVID-19 patients compared to LRTI (7.0% vs 3.6%, P=0.003), however, significantly less COVID-19 patients were discharged on anticoagulation (26.3% vs 56.4%, P=0.02). Patients who developed nAF during COVID-19 were older (P<0.001), had congestive cardiac failure (P=0.004), ischaemic heart disease (IHD) or peripheral vascular disease (PVD) (P<0.001) and a higher CHA2DS2-VASc score (P=0.02), compared COVID-19 patients who didn’t. Older age (Odds ratio (OR) 1.03, P=0.007) and IHD/PVD (OR 2.87, P=0.01) increased odds of developing nAF with COVID-19.