David was a Lecturer in Nutrition and Public Health at the London School of Hygiene and Tropical Medicine (1982-1985) and Senior Lecturer in Health Systems at the Liverpool School of Tropical Medicine (1985-1989). He joined the United Kingdom Government Foreign Office (Overseas Development Administration) as Senior Health Adviser for East Africa (1989–1990) and Chief Health and Population Adviser (1990-1997). He became Director for Human Development in the UK Department for International Development (DFID, 1997–1999). In 1999 David moved into the United Nations system starting as an Executive Director at the World Health Organization responsible for the Roll Back Malaria Project and the Office of the Director-General. He was Special Representative of the WHO Director-General for Health Action in Crises (2002-2005). He was then appointed as UN System Senior Coordinator for Avian and Pandemic Influenza (2005-2014), United Nations Secretary-General’s Special Representative for Food Security and Nutrition (2008-2014), Coordinator of the Movement for Scaling Up Nutrition (2011-2014, as Assistant Secretary-General), UN S-G’s Special Envoy for the West Africa Ebola Outbreak Response (2014-2015), and UN S-G’s Special Adviser for the 2030 Agenda for Sustainable Development and Climate Change (2016 – 2017,as Under-Secretary-General)). He was appointed, by the Director-General of WHO, as chair of the expert group on the reform of WHO’s work on outbreaks and emergencies in 2015. In October 2018, David received the World Food Prize together with Lawrence Haddad for leadership on nutrition.
David is currently Co-Director (since mid-2019) and Chair of Global Health at the Institute of Global Health Innovation, Imperial College, London. He is Strategic Director of the Swiss-based social enterprise 4SD (Skills Systems and Synergies for Sustainable Development), established in 2017, training and mentoring leaders for sustainable development. Since June 2018 David has curated the Food Systems Dialogues as a contribution to the transformation of food systems: they have involved more than 1700 leaders in 29 locations within the last 18 months. From July 2018 David contributed to preparations for the UN’s September 2019 Climate Action Summit. David co-facilitated the coalition that advanced the Nature-Based Solutions (NBS) workstream (co-led by China and New Zealand). David is co-chair of the forum on Climate Change and Health which will complete its work at the World Innovation Summit for Health, November 2020. From March 2020, David is appointed Special Envoy of WHO Director General on COVID-19.