Introduction on the global dengue epidemiological burden

Dengue disease is the most rapidly spreading mosquito-borne viral disease. Worldwide, between 2.5 and 3.6 billion people, over 40% of the population, are at risk, in over 100 endemic countries. An estimated 50 to 100 million dengue infections occur every year, of which 2 million cases evolve to severe Dengue Hemorrhagic Fever, and 21 000 would result in death. Most severe disease and deaths occur in children. The rapid global spread of dengue is due to: 1) demographic changes (i.e., population growth and land use patterns); 2) increased urban population size and density due to rural to urban migration 3) modern transportation with increased movement of people, commodities, animals, vectors and pathogens; and 4) changes in public health policies and infrastructure among other things. The geographic spread of both the mosquito vectors and the viruses has led to a global resurgence of epidemic dengue disease and emergence of severe forms in the past 25 years. Dengue is now endemic in Asia, the Pacific area, Africa, some parts of US (e.g. Puerto Rico), and Latin America (including the Caribbean). South-East Asia and the Western Pacific Regions bear nearly 75% of the dengue global disease burden. In 2010, 187,333 dengue cases were reported to the WHO SEA office; and 354,009 cases were reported to the WHO Western Pacific Region. Efforts to control the vector have limited effect on the risk for disease in humans. While geographical expansion of dengue and its vector are evident, the true burden of disease is underestimated due to constraints inherent to public health surveillance systems and the challenges specific to dengue. In the absence of an effective vaccine, public health systems focus on the early identification and early response to outbreaks. However, once a disease becomes vaccine preventable, surveillance systems become key tools to assess the performance of vaccination programs and need to be optimized to suit that purpose.