Dengue Fever: Pathophysiology

We continue our Back to College Series on Dengue Fever by bringing to you the Pathophysiology of Dengue Fever. Dengue Fever is a mosquito-borne viral disease caused by 1 of 4 closely related but antigenically distinct serotypes of dengue virus, serotypes DENV-1 through DEN-4. Infection with one dengue serotype confers lifelong homotypic immunity and a brief period of partial heterotypic immunity (2 years), but all four serotypes can eventually infect each. Several serotypes can be in circulation during an epidemic.

The Aedes mosquito

Dengue viruses transmitted by the bite of an infected female Aedes mosquito. Both males and females require nectar for energy. Females require a blood meal as a source of appropriate protein for egg development. Globally, Aedes aegypti is the predominant highly efficient mosquito vector for dengue infection, but the Asian tiger mosquito, Aedes albopictus, and other Aedes species can also transmit dengue with varying degrees of efficiency.

Virology

Dengue fever virus (DENV) is an RNA virus of the family Flaviviridae; genus Flavivirus. Other members of the same genus include yellow fever virus, West Nile virus, St. Louis encephalitis virus, Japanese encephalitis virus, tick-borne encephalitis virus, Kyasanur forest disease virus, and Omsk hemorrhagic fever virus.

Most are transmitted by arthropods (mosquitoes or ticks) and are therefore also referred to as arboviruses (arthropod-borne viruses).

Dengue Genome

The dengue virus genome contains about 11,000 nucleotide bases, which code for the three different types of protein molecules (C, M, and E). These form the virus particles and seven other types of protein molecules (NS1, NS2a, NS2b, NS3, NS4a, NS4b, NS5) found in infected host cells. Replication of the virus requires these protein molecules.

Dengue Strains

Additionally, there are five strains of the virus, called serotypes, referred as DENV-1, DENV-2, DENV-3, and DENV-4. Additionally, In 2013 DENV-5 was announced. The distinctions between the serotypes is based on their antigenicity.

Transmission

The mosquito Aedes aegypti feeding on a human host.

Transmission Species

Dengue virus is transmitted by Aedes mosquitoes, particularly A. aegypti. These mosquitoes usually live between the latitudes of 35° North and 35° South below an elevation of 1,000 meters (3,300 ft).They typically bite during the early morning and in the evening, but they may bite and thus spread infection at any time of day. Other Aedes species that transmit the disease include A. albopictus, A. Polynesians, and A. scutellaris. Humans are the primary host of the virus, but it also circulates in nonhuman primates. An infection can be acquired via a single bite.

Transmission Process

A female mosquito that takes a blood meal from a person infected with dengue fever. Moreover, During the initial 2- to 10-day febrile period, becomes itself infected with the virus in the cells lining its gut. About 8–10 days later, the virus spreads to other tissues including the mosquito’s salivary glands. Furthermore, it’s subsequently released into its saliva. The virus seems to have no detrimental effect on the mosquito, which remains infected for life.

Aedes aegypti is particularly involved, these mosquitoes breed near water and lay their eggs in the walls of water containers.

Therefore, the insects are found near water cisterns, unsealed septic tanks, decorative fountains, discarded tires and bottles or boats and other vehicles that may collect water while stationary, to live near humans, and to feed on people rather than other vertebrates.

Dengue can also be transmitted via infected blood products and through organ donation. In countries such as Singapore, where dengue is endemic, the risk is estimated to be between 1.6 and 6 per 10,000 transfusions.

Vertical Transmission

Vertical transmission (from mother to child) during pregnancy or at birth has been observed. Other person-to-person modes of transmission have also been reported, but are very unusual. The genetic variation in dengue viruses is region specific, suggestive that establishment into new territories is relatively infrequent, despite dengue emerging in new regions in recent decades.

References

  • Brady OJ, Gething PW, Bhatt S, Messina JP, Brownstein JS, Hoen AG et al. Refining the global spatial limits of dengue virus transmission by evidence-based consensus.
  • WHO Website
  • CDC Website

All Posts on Dengue

5 Trackbacks / Pingbacks

  1. Dengue Fever: Case Definition & Classification | Hidoc
  2. Dengue Fever: Historical Background & Epidemiology | Hidoc
  3. Dengue Fever: Investigation Protocol | Hidoc
  4. Dengue Fever: Signs and Symptoms | Hidoc
  5. Dengue Fever: Management Guidelines | Hidoc

Comments are closed.