Small island developing states (SIDS) are a set of islands and coastal states that share similar sustainable development challenges, as a result of their size, geography and vulnerability to climate change. Thirty-nine WHO member states in four regions – the African Region, the Region of the Americas, the South-East Asian Region, and the Western Pacific region – are classified as SIDS. Whilst the individual countries differ in many respects, collectively they face unique social, economic and environmental challenges.