Dengue fever is a common viral infection in tropical and subtropical regions that is carried and spread by mosquitoes. There has been a dramatic resurgence of epidemic dengue in the tropics worldwide. In particular, the emergence of a life-threatening complication of the illness called dengue haemorrhagic fever is a major public health concern.

There are several factors that have been identified as causing this resurgence of dengue fever and these include:

• Major global demographic changes have resulted in uncontrolled urbanization and population growth in some regions. This has led to a relative shortage of good quality housing that results in poor sanitation and inadequate sewer and waste management systems. The mosquito that carries the dengue virus breeds in the walls of water containers and inadequate maintenance of fresh water supplies in urbanized and overcrowded areas leads to increases in these mosquito populations.
• Financial difficulties and lack of human resources make it difficult to implement emergency control methods in response to dengue epidemics to prevent spread.
• In the continental United States, dengue fever is rare and the surveillance of the infection is passive, with cases of infection only being detected if a doctor reports it.
• Air travel to countries where the infection is epidemic helps to transport the infection between countries. People can pick up an infection while staying in the tropics and then transmit it to people in areas where the infection is less common.
• In endemic regions, there is usually a severe lack of effective mosquito control, which has also contributed to the spread of the infection.

Dengue fever has been recognized as a threat to public health by the National Institute of Allergy and Infectious diseases (NIAID), which funds over 60 dengue research projects to study the life threatening complications of the illness – dengue haemorrhagic fever and dengue shock syndrome. The body also funds research into the development of vaccines against the virus.