What is the biology behind dengue?

In order to understand how dengue fever propagates, one must first understand the life of the mosquitos that most often transmit the disease to people (CDC 2010a). The two types of mosquitoes that are known to harbor dengue fever virus are Aedes aegypti and Aedes albopictus (CDC 2010d).  As with all species of mosquito, aegypti and albopictus thrive in tropical environments and need stagnant water to reproduce. Female mosquitoes will lay eggs above the waterline on the inside surface of a container, and when the water level rises, the eggs are submerged under the water and will hatch, beginning the transformation from larva to pupa to adult (CDC 2009e). Mosquito eggs have been proven to be resilient to drying out, remaining viable for months without water (CDC 2010f). 

                          Boston College (Date Accessed: February 22, 2013) http://www.bc.edu/schools/cas/biology/research/infect/dengue.html

The question which follows is this: how is the mosquito itself inoculated with dengue fever virus? Ironically, it is an infected human that gives the mosquito the virus. There is a five-day period during infection when the host’s blood has a particularly high count of the dengue fever virus, and it is during this time that a mosquito may feed on the infected host’s blood and become infected itself (CDC 2010b). Having entered the mosquito, the virus then must incubate within the mosquito for one or two weeks before becoming transmittable (CDC 2010b).  The mosquito, whose lifespan may range from a few days to a few weeks, may very well die before it is able to transmit the disease to a human, which is why the chances of contracting the disease is low in areas of infrequent interaction between host and vector (i.e. southern U.S.) (CDC 2010b).  Conveniently enough for the mosquitos, humans are a source of both bloodmeals and habitat. Any open body of stagnant water, from rainwater collected in old tyres or flowerpots to the contents of damaged septic tanks, presents an opportunity for mosquitoes to lay eggs (CDC 2009f).  Mosquitos are very good at being parasites, because they capitalize on only on their hosts but also on the byproducts of their hosts’ activities.

CDC. (2012a) Entomology and Ecology. CDC.gov. Center for Disease Control. (Date Accessed: February 14, 2013.)http://www.cdc.gov/Dengue/entomologyEcology/index.html

CDC. (2012b) Epidemiology. CDC.gov. Center for Disease Control. (Date Accessed: February 14, 2013.)http://www.cdc.gov/Dengue/epidemiology/index.html

CDC. (2012d) Frequently Asked Questions. CDC.gov. Center for Disease Control. (Date Accessed: February 14, 2013.)http://www.cdc.gov/dengue/fAQFacts/index.html

CDC. (2012e) Mosquito Life-Cycle. CDC.gov. Center for Disease Control. (Date Accessed: February 14, 2013.)http://www.cdc.gov/dengue/entomologyEcology/m_lifecycle.html

CDC. (2012f) Mosquitoes’ Main Aquatic Habitats. CDC.gov. Center for Disease Control. (Date Accessed: February 14, 2013.)http://www.cdc.gov/dengue/entomologyEcology/m_habitats.html