Dengue Fever
Dengue fever, dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS) are mosquito-borne, human diseases caused by four serotype viruses from the genus, Flavivirus (DEN1, 2, 3, and 4) (Goddard 2000; Becker et al. 2003; Resh & Carde 2009). Of the dengue infections, DHF is the most severe form, and can be fatal if unrecognized (CDC 2009).
Facts and Statistics:
· Dengue is now considered to be the most important mosquito transmitted viral disease (Service 2008; CDC 2009). · Dengue virus infections cause greater rates of human morbidity and mortality worldwide than any other arbovirus (arthropod-borne virus) (Resh & Carde 2009). · Dengue has been reported in more than 100 countries (Service 2008). · Annually, approximately 2.5-3.0 billion people are at risk of being infected with dengue virus (Resh & Carde 2009). |
How is Dengue Fever Transmitted?
The mosquito, Aedes aegypti, is the most important vector of dengue, as they have a close association with humans, feeding purely on blood (Resh & Carde 2009). Other vectors also include Ades albopictus and Ades polynesiensis (Resh & Carde 2009).
Mosquitoes can transmit dengue via vertical transmission (female passes virus onto her progeny), or more commonly, via horizontal transmission (infected mosquito feeding on human host) (Goddard 2000; Resh & Carde 2009). The process of horizontal transmission is shown below (Click image for enlarged view). Usually during this process a newly infected mosquito will not feed again for 3 - 5 days. Once the infective mosquito does start feeding again, it can transmit the virus every time its mouthparts pierce a host (Goddard 2000).
The mosquito, Aedes aegypti, is the most important vector of dengue, as they have a close association with humans, feeding purely on blood (Resh & Carde 2009). Other vectors also include Ades albopictus and Ades polynesiensis (Resh & Carde 2009).
Mosquitoes can transmit dengue via vertical transmission (female passes virus onto her progeny), or more commonly, via horizontal transmission (infected mosquito feeding on human host) (Goddard 2000; Resh & Carde 2009). The process of horizontal transmission is shown below (Click image for enlarged view). Usually during this process a newly infected mosquito will not feed again for 3 - 5 days. Once the infective mosquito does start feeding again, it can transmit the virus every time its mouthparts pierce a host (Goddard 2000).
Symptoms:
In the human host, the virus is usually in incubation from 4 – 7 days, after which time the person is viremic for approximately five days (Resh & Carde 2009). The symptoms experienced are generally:
· Fever
· Headache
· Retro-orbital pain
· Intense aching
· Rash
· Mild bleeding (e.g. nose or gums bleed, easily bruised)
(Goddard 2000; Resh & Carde 2009)
If a more severe form of dengue occurs, such as DHF/DSS, a hemorrhagic shock syndrome with a fatal outcome could result (Goddard 2000). Fever will also last from two to seven days, and after it starts to decline, humans may develop symptom including (CDC 2009):
· Persistent vomiting
· Severe abdominal pain
· Difficulty breathing
Further complications can also include circulatory system failure (which could cause death), shock and possible internal bleeding (CDC 2009).
Dengue Fever - Distribution Around the World:
Dengue occurs in the tropical countries of Asia and Africa, Central and South America and the Caribbean area (Goddard 2000), which is approximately represented in the map below. CYAN represents areas with Aedes aegypti infestation, and RED represents areas with Aedes aegypti and a recent epidemic dengue fever.
In the human host, the virus is usually in incubation from 4 – 7 days, after which time the person is viremic for approximately five days (Resh & Carde 2009). The symptoms experienced are generally:
· Fever
· Headache
· Retro-orbital pain
· Intense aching
· Rash
· Mild bleeding (e.g. nose or gums bleed, easily bruised)
(Goddard 2000; Resh & Carde 2009)
If a more severe form of dengue occurs, such as DHF/DSS, a hemorrhagic shock syndrome with a fatal outcome could result (Goddard 2000). Fever will also last from two to seven days, and after it starts to decline, humans may develop symptom including (CDC 2009):
· Persistent vomiting
· Severe abdominal pain
· Difficulty breathing
Further complications can also include circulatory system failure (which could cause death), shock and possible internal bleeding (CDC 2009).
Dengue Fever - Distribution Around the World:
Dengue occurs in the tropical countries of Asia and Africa, Central and South America and the Caribbean area (Goddard 2000), which is approximately represented in the map below. CYAN represents areas with Aedes aegypti infestation, and RED represents areas with Aedes aegypti and a recent epidemic dengue fever.