Athogenesis of dengue haemorrhagic fever and
DENV serotypes can be further classified into different genotypes on the basis of nucleotide variations. During the feeding of mosquitoes on humans, DENV is presumably injected into the bloodstream, with spillover in the epidermis and dermis, resulting in infection of immature Langerhans cells epidermal dendritic cells [DC], and keratinocytes It is important to realize that coagulation enzymes can also activate the complement system, illustrating the extensive interaction that exists between the complement and the coagulation system.
Consequently, infection is amplified and virus is disseminated through the lymphatic system. Halstead SB, Yamafar C.
Shock syndrome in primary dengue infections. Certain host factors, such as glucosephosphate dehydrogenase G6PD deficiency, may also contribute to increased replication of DENV in monocytes.
Dengue pathophysiology uptodate
In this regard, it has been proposed that the coagulation responses upon severe systemic inflammation by EC in different parts of the vascular-bed system are not the same , Epidemiological observations in the Americas and in Singapore suggested that the sequence of infection with particular serotypes and the time interval between primary infection and secondary infection may play an important role in the development of DHF. Science ; Elimination of these breeding sites is an effective and definitive method of controlling the vector and therefore of preventing transmission of dengue. The actual numbers of dengue and DHF cases reported are influenced by differences in surveillance and reporting systems as well as by varying and unclear applications of case definitions, making accurate assessments of global dengue incidence and trends difficult at present. There may be flushing of the face and conjunctivitis as well as taste aberrations, anorexia, nausea, vomiting and abdominal pain. Although severe hepatic damage is not common in DENV infections, elevated liver enzymes suggest that the liver is affected, but the role of hepatic damage in coagulopathy and disease severity remains to be established. Although it is likely that the cross-reactive antibodies to self-antigens are of the short-lived IgM isotype , , vaccination strategies should not result in memory IgG responses to such antigens. During the course of the illness there is often a relative or paradoxical bradycardia in the face of increased temperature. During the DENV-2 epidemic in Cuba, it was noted that severity of disease manifestations and case-fatality rates were increased toward the end of the epidemic , , suggesting that the circulating DENV-2 might have become more virulent through passage in hosts during the epidemic. The latter may progress to hypovolemic shock dengue shock syndrome [DSS]. Bull WHO ; Further studies are needed to see if cross-reactivity of anti-NS1 with EC could lead to the increased permeability that is characteristic of DSS. In agreement with these findings it was shown in the rhesus macaque model that DENV could be recovered from some autopsy samples but not from blood. Chikungunya and dengue: a case of mistaken identity?
These innate immune mechanisms provide the host with the time needed to maximally induce the more slowly developing adaptive immunity. Minor hemorrhagic manifestations may occur in the form of petechiae, epistaxis, and gingival bleeding. Unusual clinical manifestations of dengue virus infection.
Leukopenia in dengue
Alternatively the decline in fever may be followed 1 to 3 days later by a resurgence of fever and symptoms, giving a "saddleback" appearance to the temperature curve. The failure to isolate virus from most organ samples may indicate that those tissues contained primarily degraded virus or virus complexed with antibodies that prevent infection of cells in vitro. Consequently, infection is amplified and virus is disseminated through the lymphatic system. Intravenous fluid therapy is the mainstay of treatment for patients with DHF. Mosquito cell cultures and specific monoclonal antibodies in surveillance for dengue viruses. Therefore, in studying DENV virulence, both host and viral factors should be considered. The use of mosquitoes to detect and propagate dengue viruses. New efforts are focusing on community education and behavior modification in an attempt to encourage neighborhoods to control the vector through breeding site reduction. Early studies of skin biopsy specimens indicated that the microvasculature located in the dermal papillae is the main site affected, although DENV antigen was not detected in EC but was detected in cells surrounding the microvasculature 21 , In this regard, factors that influence the amount of target cells infected, and consequently the levels of viremia, may determine the ratio of different proinflammatory and anti-inflammatory cytokines, chemokines, and other mediators, as well as the way in which the inflammatory response affects the hemostatic system 35 , Am J Epidemiol ; Mosquito-borne hemorrhagic fevers of Southeast Asia and the western Pacific. Address for reprints: Duane J. Rice L.
DENV has also been shown to have tropism for circulating mononuclear cells in blood and for cells residing in the spleen, lymph nodes, and bone marrow of infected AG mice Clearly, more efforts should be deployed in identifying the putative self-antigens that are recognized by anti-DENV antibodies and in understanding their role, if any, in dengue pathogenesis.
Virology ; In Asia, the risk of severe disease is greater in children than in adults, in contrast to the Americas, where the adult population is mainly affected and infection results in milder disease.
Prognosis of dengue fever
Dengue hemorrhagic fever: a public health problem and a field for research. Clinical studies. Centers for Disease Control, P. Convulsions may occur with the onset of fever. Minor hemorrhagic manifestations may occur in the form of petechiae, epistaxis, and gingival bleeding. Failure of hydrocortisone to affect outcome in dengue shock syndrome. Forest cycles of dengue between monkeys and mosquitoes have been described, 35 but recent techniques of studying molecular evolution in dengue viruses indicate that viruses from forest cycles in Africa do not represent a natural maintenance reservoir for epidemic dengue in humans. Binding of heterotypic antibodies to NS1 expressed on infected cells may result in complement activation 8 , Effect of temperature on the vector efficiency of Aedes aegypti for dengue 2 virus. Similar organ tropism has been observed in the primate model, with high concentrations of virus isolated from the skin and gastrointestinal tract whereas low concentrations of virus were recovered from the spleen, thymus, and several peripheral lymph nodes Adult Reye's syndrome after dengue. With regard to DENV, investigators noticed that around the time of defervescence, when plasma leakage may become apparent, high levels of the activation products C3a and C5a are measured in the plasma, followed by an accelerated consumption and a marked reduction of the complement components in patients with DSS 50 , ,
Dengue and dengue hemorrhagic fever in the Americas,
based on 49 review