Clinical Microbiology of the Dengue Virus

Topics: Dengue fever, Mosquito, Aedes aegypti Pages: 10 (3734 words) Published: October 21, 2011

The dengue virus causes dengue and dengue hemorrhagic fever. It is an arboivirus, within thia group it is from the family Flavivirade, which includes hepatitis c, West Nile, yellow fever and Japanese and St. Louis encephalitis. All these viruses are spread by mosquitoes. The two types of mosquitoes that spread dengue are Aedes aegypti and Aedes albopictus, Aedes aegypti being the most common. The virus itself is composed of single-stranded RNA and has four serotypes. These sertotypes are DEN-1, DEN-2, DEN-3 and DEN-4. The transmission cycle of dengue begins with a dengue infected person. The person will have the virus circulating in their blood, a virenia that lasts for about five days. During this period, an uninfected female Aedes Aegypti mosquito bites the person and ingests the blood. Within the mosquito, the virus replicatesduring an extrimsic incubation period for eight to 12 days. The mosquito then bites a person, which gives the virus to that person and any other person it bites during its lifetime. The virus then replicates in that person and produces symptoms, which begin to appear on an average of four to seven days, but can range from three to 14. This is known as an intrinsic incubation period. The usual signs of dengue are a fever of 103 to 105 degrees, severe headache, pain behind the eyes, body aches and pains, rash on the skin, and nausea or vomiting. Sometimes bleeding occurs. The usuaul spots for bleeing are the nose, gums or skin. Rarely, the patient suffering of dengue will develop shock, which is known as dengue shock syndrome. More that 40% of the world's population is at risk for infection from it and 1.5 million people are treated each year for dengue fever and dengue hemorrhagic fever. The first reports of major epidemics of illnesses thought to be dengue only occurred on three continents. The three continents were Asia, Africa and North America and they occurred in 1779 and 1780. However, some believe that there were epidemics dating back to the Chin Dynasty of China, which was in power from 265 to 420 A.D. Dengue has reemerged over the last 20 years and has come back with an expanded geographic distribution of both the viruses and the mosquito vectors and has increased epidemic activity. Demographic, societal and public health infrastructure changes during this period have contributed to this.


Dengue is tramsitted by an infected female mosquito. Aedes aegypti is primarily a daytime feeder and mainly bites in the morning or in the late afternoon in covered areas. It is not usuallly found in tropical forests, except in Africa. The female would rather lay her eggs in artificial containers than natural ones in fairly clean water and areas that are close to human habitation. The Aedes aegypti had been mostly eradicated during the 1950s, '60s and most of the '70s due to the spraying of DDT and other pesticides. The eradication program was discontinued during the '70s, so this species of mosquito began to reinvade the areas and countries from which it had been eradicated. By the '90s, Aedes aegypti had essentially regained all of, the land it held before the eradication program began. During the '80s, the Americas began experiencing major epidemics of the disease in countries that had not any for 35 to 130 years. Therefore, there is now a strong emphasis on having a proactive surveillance system. The objective of which is to provide early and precise information on the time, location, virus serotype and disease severity. The analysis of these four aspects are the key that is needed to predict dengue transmission and to guide implementation of control measures long before the transmission of dengue is at its peak. For exmaple, there is a dengue surveillance system in place in Puerto Rico, which provides a system in which blood samples are taken by physicians, health centers, private and public hospitals and privates laboratories in...
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