The incidence of dengue has grown dramatically around the world in recent decades. One recent estimate by Bhatt et al. indicates 390 million dengue infections per year (95% credible interval 284–528 million), of which 96 million (67–136 million) manifest clinically (with any severity of disease). Another study by Brady et al. of the prevalence of dengue, estimates that 3.9 billion people, in 128 countries, are at risk of infection with dengue viruses. An ever growing number of countries and people are at risk of infection. Dengue is now endemic in over 100 countries across the globe, and in 2013 the WHO ranked dengue as the fastest spreading vector-borne viral disease, with an epidemic potential in the world.
Dengue is a major cause of morbidity and mortality and a leading cause of hospitalization of children in many countries in tropical and subtropical areas of the world. The greatest documented burden of dengue occurs in Asia and Latin America, but the disease is now appearing in previously unaffected areas. The cost of illness to society is considerable, from lost wages and decreased productivity to costs associated with seeking care and direct medical expenses. An estimated 60% of the economic strain caused by dengue is a result of indirect costs. The cost of dengue in the Western Hemisphere alone is estimated at $2.1 billion per year.
The past 25 years have seen the emergence and reemergence of epidemic dengue, with epidemics that are larger and more frequent and cases that are more severe. By June 2010, Brazil had already recorded more cases of dengue than in any previous year, and dengue fever remains one of the leading causes of disease in Vietnam, with the number of cases continuing to increase. 2011 saw outbreaks in places as diverse as Pakistan and Kenya, and 2012 in India and Portugal.