Comorbidities including hypertension, diabetes , cardiovascular disease and age >70 appear to be associated with increased mortality amongst people infected with the Covid-19 virus. Similar co-morbidities were noted for the SARS outbreak in 2003. It has been suggested that the confluence of these risk factors is relatively concentrated amongst people treated with Angiotensin Converting Enzyme inhibitors or angiotensin II receptor antagonists (ARBs). Covid-19 agent uses the SARS-COV receptor angiotensin converting enzyme (ACE) 2 for entry into target cells. It is possible that the expression of ACE2 receptor in the virus targeted cells is increased by these drugs, increasing the risks associated with the infection. The authors of a research letter published here in the BMJ call for rapid epidemiological and pre-clinical studies to clarify this relationship.