Dengue Fever - Epidemiology

Epidemiology

Most people with dengue recover without any ongoing problems. The mortality is 1–5% without treatment, and less than 1% with adequate treatment; however severe disease carries a mortality of 26%. Dengue is endemic in more than 110 countries. It infects 50 to 100 million people worldwide a year, leading to half a million hospitalizations, and approximately 12,500–25,000 deaths.

The most common viral disease transmitted by arthropods, dengue has a disease burden estimated to be 1600 disability-adjusted life years per million population, which is similar to other childhood and tropical diseases such as tuberculosis. As a tropical disease dengue is deemed only second in importance to malaria, though the World Health Organization counts dengue as one of sixteen neglected tropical diseases.

The incidence of dengue increased 30 fold between 1960 and 2010. This increase is believed to be due to a combination of urbanization, population growth, increased international travel, and global warming. The geographical distribution is around the equator with 70% of the total 2.5 billion people living in endemic areas from Asia and the Pacific. In the United States, the rate of dengue infection among those who return from an endemic area with a fever is 2.9–8.0%, and it is the second most common infection after malaria to be diagnosed in this group.

Until 2003, dengue was classified as a potential bioterrorism agent, but subsequent reports removed this classification as it was deemed too difficult to transfer and only caused hemorrhagic fever in a relatively small proportion of people.

Like most arboviruses, dengue virus is maintained in nature in cycles that involve preferred blood-sucking vectors and vertebrate hosts. The viruses are maintained in the forests of Southeast Asia and Africa by transmission from female Aedes mosquitoes—of species other than A. aegypti—to her offspring and to lower primates. In rural settings the virus is transmitted to humans by A. aegypti and other species of Aedes such as A. albopictus. In towns and cities, the virus is primarily transmitted to humans by A. aegypti, which is highly domesticated. In all settings the infected lower primates or humans greatly increase the number of circulating dengue viruses. This is called amplification. The urban cycle is the most important to infections of humans and dengue infections are primarily confined to towns and cities. In recent decades, the expansion of villages, towns and cities in endemic areas, and the increased mobility of humans has increased the number of epidemics and circulating viruses. Dengue fever, which was once confined to Southeast Asia, has now spread to Southern China, countries in the Pacific Ocean and America, and might pose a threat to Europe.