Dengue Fever: Historical Background & Epidemiology

Dengue Fever is the most common and important arthropod-borne viral (arboviral) illness in humans. It is transmitted by mosquitoes of the genus Aedes, which are widely distributed in subtropical and tropical areas of the world (see the image below). The incidence of dengue has increased dramatically in recent decades, with estimates of 40%-50% of the world’s population at risk for the disease in tropical, subtropical, and, most recently, more temperate areas. 

A small percentage of persons who have previously been infected by one dengue serotype develop bleeding and endothelial leak upon infection with another dengue serotype. This syndrome is termed severe dengue (also known as dengue hemorrhagic fever and dengue shock syndrome).

Dengue fever is typically a self-limited disease with a mortality rate of less than 1% when detected early and with access to proper medical care. When treated, severe dengue has a mortality rate of 2%-5%, but, when left untreated, the mortality rate is as high as 20%. Globally, 2.5-3 billion individuals live in approximately 112 countries that experience dengue transmission.

Historical Background of Dengue Fever

The illness was called “the water poison” and was associated with flying insects near water.

Period: 1600 to 1800

Earliest recorded Outbreaks of febrile illnesses compatible with dengue fever have been recorded throughout history, with the first epidemic described in 1635 in the West Indies.

In 1779-1780, the first confirmed reported an outbreak of dengue fever occurred almost simultaneously in Asia, North America, and Africa.

Additionally, In 1789, the American physician Benjamin Rush published an account of a probable dengue fever epidemic that had occurred in Philadelphia in 1780. Rush coined the term breakbone fever to describe the intense symptoms reported by one of his patients.

Period: 1800 to 1900

A dengue-like epidemic in East Africa in the early 1820s was called, in Swahili. The English version of this term, “Dandy fever,” was applied to a 1827-28 Caribbean outbreak, and in the Spanish Caribbean colonies, that term was altered to “dengue.”

Eventually, dengue hemorrhagic fever epidemics occurred yearly, with major outbreaks occurring approximately every three years. This pattern has repeated itself as dengue fever has spread to new regions.

Although initial epidemics were located in urban areas, increased dengue spread has involved suburban and rural locales in Asia and Latin America.

Exceptions to Dengue Occurrence

The only continents that do not experience dengue transmission are Europe and Antarctica. Although dengue fever did not naturally occur in the European Union and continental Europe because these areas did not have an appropriate vector population to allow further spread of dengue from viremic individuals returning from other countries. However, dengue does occur in several overseas territories of European Union members. In recent decades, reports of dengue infections in long-term expatriates, aid workers, military personnel, immigrants, and travelers returning from the tropics and subtropics have been increasing and this way Dengue continues to extend its range.

Americas Dengue Occurrence

In the Americas, dengue epidemics were rare post-war because Aedes mosquitoes had been eradicated from most of the region through coordinated vector-control efforts. Moreover, systematic spraying was halted in the early 1970s because of environmental concerns. By the 1990s, An aegypti mosquitoes repopulated most of the countries in which they had been eliminated.

Recent Occurrence

In 2014, increased cases of dengue were reported to the WHO in which experienced an outbreak of dengue serotype 3 (DENV-3) after a 10-year hiatus. In 2015, large outbreaks of dengue were reported in the Philippines (>169,000 cases), Malaysia (>111,000 suspected cases), and Brazil (>1.5 million cases). Delhi, India, experienced its worse outbreak since 2006.

WHO surveys indicated that more than 44% of the population was infected, with only mild disease reported. The first dengue hemorrhagic fever epidemic in the Americas occurred in Cuba in 1981. Additionally, it  involved serotype two dengue (DENV-2), with hundreds of thousands of cases of dengue in both children and adults. It included 24,000 cases of dengue hemorrhagic fever, 10,000 cases of dengue shock syndrome, and 158 reported deaths.

In 1997, Asian genotype DENV-2 was reintroduced. Dengue shock syndrome and dengue hemorrhagic fever were seen only in adults that had been infected with DENV-1 in 1977. Disease and case-fatality rates were higher in those who had been infected with DENV-2 even 20 years after their initial DENV-1 infection than those who have infected four years apart.

Data from other countries support the finding that the severity of secondary dengue infections appears to intensify with longer intervals between infections.  Since then, dengue fever and dengue hemorrhagic fever cases have progressively increased.

Factors responsible for the Spread of Dengue:

  • Explosive population growth
  • Unplanned urban overpopulation with inadequate public health systems
  • Poor control of standing water and vectors
  • Viral evolution
  • Increased international recreational, business, and military travel to endemic areas

All of these factors must be addressed to control the spread of dengue and other mosquito-borne infections. Unplanned urbanization is believed to have had the largest impact on disease amplification in individual countries. Moreover, travel is believed to have had the largest impact on global spread.

Epidemiology

The overall incidence of dengue, as well as the explosive outbreaks of dengue, has been increasing dramatically over the last several years. Older data suggested an estimated 50-100 million cases of dengue fever.

The data also suggests 500,000 cases of dengue hemorrhagic fever occur worldwide, with 22,000 deaths (mainly in children). However, In 2015, official data from WHO member states reported more than 3.2 million cases. Moreover, out of these 2.35 million cases were in the Americas alone. These included 10,200 cases of severe dengue and 1181 deaths.

An estimated 2.5-3 billion people in approximately 112 tropical and subtropical countries worldwide are at risk for dengue infection. In other words approximately 40%-50% of the world’s population is at risk of infection. The only continent that has not experienced dengue transmission is Antarctica.

According to the World Health Organization, dengue ranks as the most important mosquito-borne viral disease in the world. In the last 50 years, the incidence of dengue has increased 30-fold worldwide. In the Americas cases of dengue rose by 640,000 and of  dengue hemorrhagic by 19,000 cases in 12 years.

References:

World Health Organization. Dengue and severe dengue fact sheet. WHO. Available here. April 2017; Accessed: September 28, 2017.

WHO. Dengue fever and dengue hemorrhagic fever prevention and control. World Health Assembly Resolution WHA55.17, adopted by the 55th World Health Assembly, 2002. 3. WHO. Revision of the International Health Regulations. World Health Assembly

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