From MicrobeWiki, the student-edited microbiology resource
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| ==Types of DENV strains== | | ==Viral Replication== |
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| There are multiple ways to classifications DENV srains depending on the context.Dengue viruses maintaining transmission mostly between nonhuman primates and forest dwelling <I>Aedes aegypti</I> are considered sylvatic. It was once thought that sylvatic strains were less virulent than epidemic or endemic strains of DENV. Some believed sylvatic strains lacked the potential to cause virulent epidemics because cases of sylvatic dengue fever are rare when compared to overall incidence of of dengue fever. As it turns out, sylvatic strains share the same pathogenic potential as strains found in urban areas. There are reported cases dengue hemorrhagic fever from infection with sylvatic DENV. The destruction of forest areas where sylvatic strains of DENV are maintained has not even lead to a decrease in outbreaks of sylvatic DENV in West Africa [18].
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| Epidemic and endemic DENV strains infect and replicate within humans and domesticated <I>Aedes</I> species [9].
| | [[File:Viral replication and genome.jpg|400px|thumb|center|Figure ?. DENV (+)ssRNA genome and schematic of virion replication within the host cell.[DHF has link 21]] |
| The distinction between epidemic and endemic dengue has become hazy as epidemic strains of DENV have become endemic in tropical urban slums. In areas where there is poor sanitation, free standing water, high population density, and constant human traffic allow continuous transmission of the virus (Figure 1)[4,8]. Epidemic strains of DENV are best transmitted by <I>Aedes ageypti</I> mosquitoes but can be transmitted less efficiently by other <I>Aedes</I> species and cause[19]. Epidemic strains can also produce large fast moving epidemics if a number of factors create high density vectors populations in close proximity to high density host populations [20].
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| Invassive species are defined as strains or genotypes of DENV not previously seen in a particular area or geographic region [14]. They tend to cause large epidemics because the population in that area does not have homologous immunity to the virus. Noninvasive species are endemic to the area and maintain slow continued transmission. Invassive species can be more virulent than noninvassive strains but this is dependent on host population susceptibility all of the strains of DENV circulating in the area at that given time. An invasive strain can colonize a given area if it can outcompete other DENV strains for susceptible hosts, eventually becoming and established endemic strain to the area.The differentiation between innvassive and noninvassive is an arbitrary tern to differentiate between established and new species of DENV.
| | DENV is a positive strand RNA virus, so once it is endocytosed by the host cell and escapes the endosome it can immediately begin translation of its genome. Like other (+)ssRNA viruses it must transcribe a negative strand RNA template to transcribe new copies of its genome. |
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| DENV can also be classified according to genotype. The two most common genotypes mentioned in the literature are American and Southeast Asian because of their well documented differences in virulence. American genotype strains tend to be less virulent as well as less competitive than Southeast Asian genotype strains.
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Revision as of 17:11, 7 December 2010
Viral Replication
Figure ?. DENV (+)ssRNA genome and schematic of virion replication within the host cell.[DHF has link 21
DENV is a positive strand RNA virus, so once it is endocytosed by the host cell and escapes the endosome it can immediately begin translation of its genome. Like other (+)ssRNA viruses it must transcribe a negative strand RNA template to transcribe new copies of its genome.
