Dengue is the most rapidly spreading mosquito-borne viral disease in the world. Infection may be subclinical or may lead to severe disease with vascular leakage, shock and death. Management of severe disease relies on prompt fluid resuscitation and frequent re-evaluation. In non-endemic countries the diagnosis is usually not confirmed during the acute illness. Dengue should be considered in any unwell traveller presenting within 2 weeks of leaving an endemic area. © 2010 Elsevier Ltd.