Data and statistics
The incidence of dengue has grown dramatically around the world in recent decades. Over 2.5 billion people are now at risk. WHO estimates there may be 50–100 million dengue infections worldwide every year. Before 1970, only 9 countries had had severe dengue epidemics, but the disease is now endemic in more than 100 countries and territories in 5 WHO regions: Africa, the Americas, the Eastern Mediterranean, South-east Asia and the Western Pacific. The Americas, South-east Asia and the Western Pacific are the most seriously affected. Cases across these regions exceeded 1.2 million in 2008 and 2.3 million in 2010 (according to official data submitted by Member States). The number of reported cases has continued to increase. In 2010, 1.6 million cases of dengue were reported in the Americas alone, of which 49 000 were severe.
Chikungunya occurs in Africa and Asia, including the Indian subcontinent. Human infections in Africa have been at relatively low levels for some years, but there were a large outbreak in the Democratic Republic of the Congo in 1999–2000 and an outbreak in Gabon in 2007. Starting in February 2005, a major outbreak occurred in islands of the Indian Ocean. A large number of imported cases in Europe was associated with this outbreak, mostly in 2006 when the Indian Ocean epidemic peaked. A large chikungunya outbreak occurred in India in 2006 and 2007, and affected several other countries in South-East Asia. Transmission was reported for the first time in Europe in 2007, in a localized outbreak in north-eastern Italy.