Dengue Virus

Dengue Virus
	;
Virus classification
Group:	Group IV ((+)ssRNA)
Family:	Flaviviridae;
Genus:	Flavivirus;

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Main Article

Discussion

Classification

Group: Group IV ((+)ssRNA)

Family: Flaviviridae

Genus: Flavivirus

Species: Dengue Virus

Description and significance:

The Dengue Virus, pronounced as [deng – gey or deng – gee] is a category-A pathogen and therefore is a serious threat to the human population globally. Category A pathogens are microbes that are hazardous to lab personnel and have the potential to cause serious epidemic disease. The Dengue Virus has four different serotypes, DEN-1, DEN-2, DEN-3 and DEN-4. These four serotypes are approximately 60-80% homologous but different enough to restrict cross immunity. This means that if a person is infected with one type of the four Dengue virus strains, they will build immunity to that specific serotype, but not for the other three. This lack of cross immunity is what poses a problem in the development of a vaccine for Dengue. The Dengue virus causes a less lethal condition known as Dengue Fever, which is also known as the breakbone fever. The Dengue virus causes a more lethal condition in some who are infected and that is known as the Dengue Hemorrhagic Fever (DHF) and Dengue Shock Syndrome (DHS).

The Dengue virus is currently believed to be the most common mosquito-borne disease in recent times and cause for increased international health concerns. The Dengue virus currently poses a risk to approximately 2.5 billion people of the worlds total population. In other words, almost one third of the world is at risk for this potentially deadly virus. The Dengue virus is transmitted amongst humans via its main vector, the Aedes aegypti mosquito. This virus is mostly found in countries along the equator and in countries with tropical and subtropical conditions because these are the conditions needed for this mosquito to thrive in. The mosquito acquires the disease from an infected individual and then carries it and passes it on to other individuals it feeds off of. Once an individual has been infected the virus then causes the person to come down with Dengue Fever. Dengue fever is a febrile disease and has Flu like symptoms accompanied by a rash and severe aches and pains. Headaches are extremely common and stronger than normal. Joint pain is also very common. Dengue Fever will usually subside in approximately five to ten days. Dengue Hemorrhagic Fever is the more serious complication caused by the Dengue Virus. Dengue Hemorrhagic Fever has an incubation period that is similar to Dengue Fever (approximately 3-5 days) but unless treated with a combination of corticosteroids, proper hydration and physician supervision, DHF will be mortal for the individual. Dengue Hemorrhagic Fever causes the blood vessels to become excessively permeable accompanied by thrombocytopenia and abnormal hemostasis.

Natural Host:

The Dengue virus has a host cycle of Human-Aedis agypti-Human, where the human acts as a host and resevoir for this virus and the mosquito is the primary and extremely efficient vector. The initial host for this virus is the infected human. When a female A. aegypti mosquito feeds on the infected human she bites into the blood stream of the human and injects a anticoagulant into the blood. While she is feeding, the virus is transmitted to the mosquito. The virus then replicates within the mosquito and is transmitted to the next human that she feeds upon while injecting it with the anticoagulant. The mosquito primarily functions as an effective vector but also plays host in between transmission because this is where the acquired Dengue virus strain is being replicated prior to being injected into the next human victim.

When was your organism discovered?

An encyclopedia of disease symptoms and remedies from the Chin Dynasty contains the earliest possible records of the Dengue virus. The encyclopedia was originally written around 265 to 420 and was formally edited in 610 A.D. under the Tang Dynasty and then again in 992 A.D. under the Northern Sung Dynasty. The disease that the Chinese were talking about was called “water poison” and was thought to be somehow connected with flying insects that were associated with the water.

Dr. Benjamin Rush discovered, identified and documented the first case of Dengue Fever back in 1779. Dr. Rush is the person responsible for calling it the “breakbone” fever. During the timeframe of 1779-1780 the first of multiple Dengue Fever reports were recorded across Asia, Africa and North America. Dengue Fever was a known disease in North America back in that time but in more modern times, outbreaks of Dengue has not been too significant. The only recorded occurences of Dengue via the Aegypti mosquito has only been recorded six times since 1975 in the state of Texas. (Need to cite)

How and where it was isolated:

In more recent times, cases of Dengue have been isolated from Pakistan to the Americas. The first ever Dengue viruses were isolated from soldiers who fell sick in Calcutta, India, New Guinea and Hawaii. The viruses from India, Hawaii and one strain from New Guinea were Antigenically similar, whereas three other strains from New Guinea appeared to be different. They were called Dengue 1 (DEN-1) and Dengue 2 (DEN2) and designated as prototype viruses (DEN-1, Hawaii and DEN-2, New Guinea-C). Two more serotypes - Dengue 3 (DEN-3) and Dengue 4 (DEN-4) were subsequently isolated from patients with a hemorrhagic disease during an epidemic in Manila in 1956.

Genome structure:

Interesting Features and Facts:

Dengue Virus is not a single virus it has four different Serotypes.

- DEN-1, DEN-2, DEN-3, DEN-4

It cannot be transmitted by any of the following

- Saliva

- Hugging

- Handshaking

- Breathing

- Sexual Intercourse

It can only be transmitted via its small yet efficient vector, the female Aedes aegypti Being infected the first time may cause Dengue Fever with any of the four strains and the infected body may develop immunity to that specific strain. Infection a second time by any of the remaining three will cause Dengue Hemorrhagic Fever.

Vaccines have been developed but none have worked to provide cross immunity against all four serotypes in order for them to be successful. Technology and tools to perform Dengue Virus tests on the Aedes aegypti do not exist as of yet.

How does this organism cause disease?

What makes it biologically interesting?

Why should a disease from the third world, underdeveloped and tropical regions of this world bother anyone not near the affected regions?

What makes the Dengue virus so very interesting is that only around 200 years ago, it was a rare and isolated situation of someone dying of Dengue Fever or Dengue Hemorrhagic Fever. Today, this virus puts over 2.5 billion, that’s approximately one-third of the global population at risk. The major spread of this disease happened in this century after World War II when soldiers who had it were moved around. It is interesting to know that so little is known about this virus or its multiple serotypes because the proper technology does not exist to carry out the required experiments on the Aedes aegypti. It’s also interesting to know that resistance to one strain does not mean nor permit resistance to the other remaining three strains, leaving the victim vulnerable to now developing Dengue Hemorrhagic Fever with no clear cut treatment available.