Calum has studied severe virus disease outbreaks since 1988 in the fields of diagnostics, clinical characterisation and clinical trials. He was a founding member of ISARIC. 

He has led studies of COVID-19, MERS, Monkeypox, Ebola (EVD and Survivors), Influenza and Bronchiolitis, at times field-deployed in austere circumstances. He and his team were awarded the Queen’s Ebola Medal for Service in West Africa, and a Commonwealth Association Award for their work with Ebola Survivors.

He is a UK Government Senior Clinical Government Advisor siting on the Scientific Advisory Group for Emergencies (SAGE) for the COVID-19 response, and the New Emerging Respiratory Viral Treats Advisory Group (NERVTAG) for Gov.UK. He is a former member of the WHO Scientific Technical Advisory Committee for Ebola Emergency (STAC-EE), and the Gov.UK Pandemic Flu group. He was appointed Honorary Respiratory Physician at Alder Hey Children’s Hospital Liverpool in 2006.