Dengue fever is no longer just an imported threat arriving on airplanes. It's a homegrown reality in Catalonia. By the summer of 2024, the outbreak of eight cases in Vila-seca (Tarragonès) –the largest recorded in Spain– forcefully confirmed it: the virus is circulating here, transmitted by native mosquitoes. This episode is not an anecdote, but an alarming sign that reflects a profound transformation: global warming and mass mobility have shattered old epidemiological boundaries. A patient with fever and bone pain can no longer rule out a tropical disease without traveling. Faced with this new normal, the response cannot be fragmented. Human, animal, and environmental health are intrinsically linked. The solution has a name, One Health', an integrative approach that becomes an imperative necessity.