Dr Tedros Adhanom Ghebreyesus, WHO’s director-general, expressed profound sadness, praising Sir David's dedication to global health and equity.
Sir David spent 17 years at the United Nations, where he expanded nutrition programmes and addressed health crises including malaria, bird flu, and Ebola.
He was appointed as the WHO's special envoy for Covid-19 in 2020, becoming a regular presence on news programmes throughout the pandemic.
Sir David was knighted at Buckingham Palace in March 2023 in recognition of his outstanding contributions to global health.