Dengue virus is the fastest growing vector-borne disease today. According to the Centers for Disease Control and Prevention (CDC), there are an estimated 400 million dengue infections each year in over 125 countries.
Dengue symptoms range from mild and flu-like to high fever, rash, severe headache, pain behind the eyes, muscle and joint pain. The joint pain can be so severe that dengue has also been given the name ‘breakbone fever’. Nausea, vomiting, and loss of appetite are also common. In the more severe form, dengue haemorrhagic fever (DHF) blood vessels start to leak and cause bleeding from the nose, mouth, and gums. Without prompt treatment, the blood vessels can collapse, causing shock (dengue shock syndrome) and ultimately fatality.
In addition, there are a range of atypical manifestations of dengue, including neurological disorders (Guillain-Barré syndrome, meningoencephalitis, encephalitis, encephalopathy), and gastrointestinal, lymphoreticular, cardiovascular, renal and musculoskeletal conditions.
Dengue is caused by four closely related viruses (serotypes), with recent research suggesting there is also a 5th serotype. Once infected, a person can develop a lifelong immunity to that strain of the virus but can become more susceptible to the other three strains. As many as 50% of dengue infected individuals do not show symptoms of the disease.
Before 1970, only nine countries experienced severe dengue epidemics and they were largely confined to Southeast Asia. This was likely due to the success of the Pan American Health Organization’s Aedes aegypti eradication program that started in the 1950s, which protected the Americas from severe epidemics. Discontinuation of this program in the 1970s allowed the Americas to become re-infested with Aedes aegypti mosquitoes, and large numbers of dengue haemorrhagic fever cases began to appear in the Caribbean and Latin America in 1981.
Severe dengue is now endemic in more than 100 countries in Africa, the Americas, the Eastern Mediterranean, South-East Asia and the Western Pacific. There are around 500,000 annual cases of dengue haemorrhagic fever every year, resulting in an estimated 22,000 deaths. Severe dengue has become a leading cause of hospitalization and death among children in Asian and Latin American countries. Dengue is also an extremely expensive disease, estimated to cost the global economy over US$39 billion in 2011 alone.
There is a single vaccine for dengue available in certain endemic countries, with further vaccine candidates still in the development stage. This vaccine reduces dengue in less than 70% of people vaccinated, and is not recommended for children under 9 or adults over 45.