With the warming effect of climate change, the areas where the disease and its host can survive are expected to grow, and in many of the areas in which dengue fever is presently found, its virulence is likely to increase (McMichael and others, 2003). Dengue is one of the world’s most important vector-borne diseases, affecting more than 2.5 million people worldwide (see box II.1). Most of the reported fatalities from this disease have been among children and young adults (Centers for Disease Control and Prevention, Division of Vector-Borne and Infectious Diseases, 2008; World Health Organization, 2009). More than 600 million young men and women live in areas infested with the Aedes aegypti mosquito, which transmits dengue, and both the mosquito and the incidence of the disease have experienced a dramatic resurgence since the 1970s (Centers for Disease Control and Prevention, Division of Vector-Borne and Infectious Diseases, 2008).
Box II.1 Dengue: a resurgent virus Dengue is a mosquito-borne viral infection that causes a severe flu-like illness, and in some cases a potentially lethal complication called dengue haemorrhagic fever (DHF) may develop. Dengue occurs in tropical and subtropical regions, typically in and around urban areas, and in recent years has become a major international public health concern. Over the past few decades the incidence of dengue has grown dramatically. According to World Health Organization estimates, some 50 million people may be infected with the virus each year. In 2007 alone there were more than 890,000 cases of dengue reported in the Americas, and 26,000 of these were DHF. Today, dengue is endemic in more than a hundred countries in Africa, the Americas, the Eastern Mediterranean, South-East Asia, and the Western Pa-
cific, with the last two regions being the most seriously affected. The past six years have seen unusually high rates of dengue infection in South-East Asia and the Western Pacific, and climate change may be partly to blame. The Aedes aegypti mosquito, which transmits the virus, does better in warm, wet weather, and with climate change, these regions have experienced rising temperatures and longer rainy seasons. Climate change is not the only factor influencing the resurgence of dengue. Increased urban migration and poor sanitation and water storage are also significant contributors, especially in developing countries. Even in the more developed countries of a vulnerable region, however, the problem has grown more acute. For example, Singapore, a model of dengue control, saw a major outbreak in 2005 and, following a 2006 decline, increased incidence in 2007. As temperatures continue to rise it will become more difficult to prevent the spread of the disease, even with improved fumigation and prevention methods. There is no specific treatment for dengue fever. Sources: Krista Mahr (2007), “Vagabond virus: dengue fever is spreading, and some think climate change is to blame”, p. 38; and World Health Organization (2009), “Dengue and dengue haemorrhagic fever”.
…and increase the threat of heat stress The rising temperatures climate change brings can increase the incidence of heat stress and heat-related mortality, and those without adequate housing or health services are most vulnerable to this threat (McMichael and others, 2003). According to figures compiled by
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