Early immune activation in acute dengue illness is related to development of plasma leakage and disease severity.
T lymphocyte activation and increased cytokine levels have been described in retrospective studies of children presenting with dengue hemorrhagic fever (DHF). Serial plasma samples obtained in a prospective study of Thai children presenting with <72 h of fever were studied. Plasma levels of 80-kDa soluble tumor necrosis factor receptors (sTNFRs) were higher in children who developed DHF than in those with dengue fever (DF) or other nondengue febrile illnesses (OFIs) and were correlated with the degree of subsequent plasma leakage. Soluble CD8 and soluble interleukin-2 receptor levels were also elevated in children with DHF compared with those with DF. Interferon-gamma and sTNFR 60-kDa levels were higher in children with dengue than in those with OFIs. TNF-alpha was detectable more often in DHF than in DF or OFIs (P<.05). These results support the hypothesis that immune activation contributes to the pathogenesis of DHF. Further studies evaluating the predictive value of sTNFR80 for DHF are warranted. (+info)
Variation in oral susceptibility to dengue type 2 virus of populations of Aedes aegypti from the islands of Tahiti and Moorea, French Polynesia.
Twenty three samples of Aedes aegypti populations from the islands of Tahiti and Moorea (French Polynesia) were tested for their oral susceptibility to dengue type 2 virus. The high infection rates obtained suggest that the artificial feeding protocol used was more efficient than those previously described. Statistical analysis of the results allowed us to define two distinct geographic areas on Tahiti with respect to the susceptibility of Ae. aegypti: the east coast, with homogeneous infection rates, and the west coast, with heterogeneous infection rates. No geographic differences could be demonstrated on Moorea. The possible mechanisms of this phenomenon are discussed in connection with recent findings on the variability of susceptibility of Ae. aegypti to insecticides. (+info)
Serologic evidence for an epizootic dengue virus infecting toque macaques (Macaca sinica) at Polonnaruwa, Sri Lanka.
Dengue is one of the most rapidly emerging diseases in the tropics. Humans are the principal reservoir of dengue viruses. It is unclear if nonhuman primates also serve as a reservoir of human dengue viruses under certain conditions. In this study, a cross-sectional serologic survey was carried out to characterize the pattern of transmission of a recently identified dengue virus among toque macaques in Sri Lanka. The results indicated that an epizootic dengue virus was active among the macaques. A single epizootic had taken place between October 1986 and February 1987 during which 94% of the macaques within the 3 km2 study site were exposed to the virus. The epizootic was highly focal in nature because macaques living 5 km from the study population were not exposed to the virus. The transmission of dengue viruses among macaques in the wild may have important public health implications. (+info)
Bacterial lipopolysaccharide inhibits dengue virus infection of primary human monocytes/macrophages by blockade of virus entry via a CD14-dependent mechanism.
Monocytes/macrophages (MO/Mphi) are the major target cells for both dengue virus (DV) and bacterial lipopolysaccharide (LPS), and the aim of this study was to define their interactions. We had found that LPS markedly suppressed DV infection of primary human MO/Mphi when it was added to cultures prior to or together with, but not after, viral adsorption. The inhibitory effect of LPS was direct and specific and was not mediated by LPS-induced secretion of cytokines and chemokines such as tumor necrosis factor alpha, interleukin-1beta (IL-1beta), IL-6, IL-8, IL-12, alpha interferon, MIP-1alpha, and RANTES. In fact, productive DV infection was not blocked but was just postponed by LPS, with a time lag equal to one viral replication cycle. Time course studies demonstrated that LPS was only effective in suppressing DV infection of MO/Mphi that had not been previously exposed to the virus. At various time points after viral adsorption, the level of unbound viruses that remained free in the culture supernatants of LPS-pretreated cultures was much higher than that of untreated controls. These observations suggest that the LPS-induced suppression of DV replication was at the level of virus attachment and/or entry. Blockade of the major LPS receptor, CD14, with monoclonal antibodies MY4 or MoS39 failed to inhibit DV infection but could totally abrogate the inhibitory effect of LPS. Moreover, human serum could significantly enhance the LPS-induced DV suppression in a CD14-dependent manner, indicating that the "binding" of LPS to CD14 was critical for the induction of virus inhibition. Taken together, our results suggest that LPS blocked DV entry into human MO/Mphi via its receptor CD14 and that a CD14-associated cell surface structure may be essential for the initiation of a DV infection. (+info)
A deviation bar chart for detecting dengue outbreaks in Puerto Rico.
OBJECTIVES: A Centers for Disease Control and Prevention deviation bar chart (Statistical Software for Public Health Surveillance) and laboratory-based surveillance data were evaluated for their utility in detecting dengue outbreaks in Puerto Rico. METHODS: A significant increase in dengue incidence was defined as an excess of suspected cases of more than 2 SDs beyond the mean for all 4-week periods from April through June (the period of lowest seasonal incidence), 1989 through 1993. An outbreak was defined as a cumulative annual rate of reported dengue greater than 3 per 1000 population. RESULTS: Retrospective application of the system to 1994 data showed agreement with previous analyses. In 1995 and 1996, 36.4% and 27.3%, respectively, of municipalities with a significant increase in reports for 2 or more consecutive weeks before the first week of September had an outbreak, compared with 9.0% (in 1995, P = .042) and 6.0% (in 1996, P = .054) of towns without a significant increase. The system showed sensitivity near 40%, specificity near 89%, and accuracy in classifying municipalities near 84%. CONCLUSIONS: This method provides a statistically based, visually striking, specific, and timely signal for dengue control efforts. (+info)
Effects of dengue fever during pregnancy in French Guiana.
To determine the effects of dengue fever (DF) during pregnancy, pregnant women presenting with a dengue-like syndrome at a hospital in Saint-Laurent du Maroni, French Guiana, from 1 January 1992 to 1 April 1998 were studied. The diagnosis of DF was made by serological tests, virus isolation on AP 61 mosquito cells, and/or reverse transcriptase polymerase chain reaction analysis. Twenty-two women had either probable or confirmed DF. Dengue virus serotype 2 was detected in four cases, and dengue virus serotype 1 was detected in one. Three fetuses died following the onset of the disease, and three cases of prematurity occurred. All infants appeared normal during physical examination, and no neonatal DF was diagnosed. In conclusion, DF in pregnant women did not cause any infant abnormality, but it may have been responsible for fetal death. The rate of fetal death associated with DF (13.6%) was much higher than the mean rate for the gynecology unit at the hospital (1.9%). However, these differences were not significant, and consequently these preliminary results need to be confirmed. (+info)
Evaluation of the MRL diagnostics dengue fever virus IgM capture ELISA and the PanBio Rapid Immunochromatographic Test for diagnosis of dengue fever in Jamaica.
We evaluated two new commercial dengue diagnostic tests, the MRL Diagnostics Dengue Fever Virus IgM Capture ELISA and the PanBio Rapid Immunochromatographic Test, on serum samples collected during a dengue epidemic in Jamaica. The MRL ELISA method correctly identified 98% (78 of 80) of the samples as dengue positive, while the PanBio test identified 100% (80 of 80). Both tests were 100% (20 samples of 20) specific. (+info)