Communicable disease control is a long-standing policy area, growing in importance the more human beings and other disease vectors are able to travel long distances and across borders. Individuals, governments and international organisations all affect the transmission and control of communicable diseases. Despite the EU being a relatively late entrant into the history of communicable disease policy, its influence in communicable disease policy, and, latterly, law, reflects broader dynamics in European integration. EU communicable disease policy and EU law lead to social and political spillover, which itself leads to further integration. EU communicable disease law and policy is particularly entwined with the ‘precautionary principle’.