Changes in the epidemiology of dengue, as described above,led to problems with the use of the earlier WHO classification which grouped symptomatic dengue virus infections into three categories: undifferentiated fever, dengue fever and dengue haemorrhagic fever (DHF).Many problems with this classifi-cation have been reported 17–21 including difficulty classifying all cases precisely, epidemiological changes with increasing age,classifying the severity of dengue based on primary or secondary presentation, and the presence of secondary infections which play a major role in morbidity. A negative tourniquet test may not be sufficient to exclude a diagnosis of DHF in a febrile patient, necessitating redefinition of clinical criteria. A WHO supported prospective multicentre clinical study in endemic regions concluded that severe dengue and non-severe dengue could be clearly distinguished by combining clinical and/or laboratory parameters. The revised classification is more practical in terms of decision-making,ategorisation of severity and planning management (figure 1) and also makes surveillance easier. The most important management strategy in dengue is early recognition of the different phases of the disease, which are clearly elucidated along with rational management algorithms in the revised classification.From a practical point of view, serial haematocrits are very useful since they can be performed every few hours to monitor the development or severity of leakage. A micro-haematocrit centrifuge should be considered an essential piece of equipment on any ward treating patients with severe dengue.Accumulation of fluid in multiple body compartments becomes detectable typically at the time fever disappears and is well demonstrated on both CT and ultrasound examinations.Ultrasonography has been reported to be superior to laboratory parameters and radiography in detecting plasma leakage.Gallbladder wall thickening is significantly associated with severe dengue, along with thrombocytopenia and elevated haematocrit or haemoconcentration.