Showing papers on "Dengue fever published in 1993"

Emergence of epidemic dengue/dengue hemorrhagic fever as a public health problem in the Americas.

Abstract: The incidence of dengue and dengue hemorrhagic fever has increased dramatically in the past 15 years in most urban centers of the tropics. Coincident with this increase has been the emergence of epidemic dengue hemorrhagic fever in the American region. The current changing disease pattern in the Americas is very similar to that which occurred in southeast Asia 30 years ago. The similarities in the evolution of severe disease in the two regions and the possible reasons for the changing disease pattern are discussed.

Failure of High-Dose Methylprednisolone in Established Dengue Shock Syndrome: A Placebo-Controlled, Double-Blind Study

Abstract: Objective. Steroids are widely used in Thailand and other dengue-endemic countries to treat severe dengue shock syndrome. This study was designed to determine whether a single high dose of methyiprednisolone will reduce mortality in children with dengue shock syndrome who did not respond to simple fluid and plasma replacement therapy. Methods. A prospective, randomized, doubled-blind, controlled trial was conducted in two hospitals in Khon Kaen Thailand during June to September in 1987 and 1988. Sixty-three children with severe dengue shock syndrome were randomized into two groups; the first group received a single dose of methylprednisolone (30 mg/kg) and the second group received placebo. Results. There was no significant difference in mortality between the two groups (P = .63). The mortality rate was 12.5% (4/32) in the steroid group and 12.9% (4/31) in the group that received placebo. The sequelae at 2 weeks among treatment and control survivors were not significantly different These two groups were comparable in age, sex, severity of illness, and duration of shock at the outset of the study. The two treatment groups were similar in subsequent hospital course as determined by maximum and minimum hematocrit level and bleeding severity. The numbers of patients in each group who had liver failure and evidence of disseminated intravascular clotting defect were also comparable. Complications such as occurrence of fever after shock, pneumonia, convulsion, cardiac arrest, pulmonary hemorrhage, and positive hemoculture were not significantly different in the treatment and control groups. Conclusions. A single high dose of methylprednisolone does not reduce mortality in severe dengue shock syndrome which does not respond to conventional critical care.

High levels of interferon alpha in the sera of children with dengue virus infection

Abstract: We measured the levels of interferon alpha (IFNα) in the sera of Thai children hospitalized with dengue hemorrhagic fever (DHF) or dengue fever (DF) to examine the role of IFNα in dengue virus infections of humans. The percentage of patients who had detectable levels of IFNα (≥ 3 U/ml) was higher in patients with DHF (80%, P < 0.001) and in patients with DF (60%, P < 0.001) than in healthy Thai children (7%). The levels of IFNα were higher in patients with DHF and in patients with DF on the first few days after the onset of fever than in healthy Thai children. The average levels of IFNα in patients with DHF were high two days before defervescence, decreasing gradually until the day of defervescence. There was a subset of patients with DHF who had increasing levels of IFNα after defervescence. However, the levels of IFNα in patients with DF were not high after fever subsided. The levels of IFNα were not different among children with DHF grades 1, 2 and 3. Among patients with DHF, T lymphocytes were activated to a higher degree in high IFNα producers than in low IFNα producers. These results indicate that similarly high levels of IFNα are produced in vivo during the acute stages of DHF and DF, and that high levels of IFNα remain after fever subsides in some patients with DHF, but not in patients with DF.

Surveillance of the circulation of arbovirus of medical interest in the region of eastern Senegal

Abstract: A study about the circulation of arboviruses of medical interest in southeastern Senegal was conducted from 1988 to 1991, during and around the periods of transmission. Specific IgM antibodies were detected by ELISA test in human sera, as a sign of a recent infection within 2 to 5 months. The comparison of the serological IgM results from human surveys in different villages, and the isolations of arboviruses from mosquitoes during the same period of time permitted a rapid and global evaluation of the circulation of these viruses. A low level of yellow fever virus activity was detected both in humans and mosquitoes in 1988 to 1990. A dengue 2 epizootic occurred in 1989-1990. Dengue 2 virus was isolated from humans and mosquitoes in 1990. Some dengue 2 outbreak may occur in the upcoming years. A Zika virus epizootic outbreak was observed each year. A human strain was isolated in 1990. The other flaviviruses (West-Nile, Kedougou, Wesselsbron), Chikungunya virus, Rift Valley Fever virus and Crimean-Congo Hemorrhagic Fever virus did not seem to present a major public health concern in southeastern Senegal.

Unusual neurologic manifestations occurring during dengue fever infection.

Abstract: This is a report on dengue fever in two young patients in France that were infected in New Caledonia and Thailand. Both presented with unusual neurologic manifestations. The first patient developed a focal subarachnoid hemorrhage that was associated with transient thrombocytopenia. No neurologic vascular malformation was detected; a mild dengue hemorrhagic fever after a previous dengue infection was suspected. The second patient showed peripheral facial palsy one week after apyrexia without any other etiology except the dengue infection. This case was probably a postinfectious syndrome associated with dengue virus. Both patients recovered spontaneously. The circumstances of the neurologic manifestations in these patients may be attributed to the dengue fever virus. However, although neurologic complciations reported for dengue fever are unusual, it is reasonable to consider these manifestations as being due to immunopathologic consequences.

Fulminant hepatitis in dengue infection.

Abstract: Eight cases of liver failure and encephalopathy were observed among twenty cases of grade 3 and grade 4 dengue hemorrhagic fever/dengue shock syndrome admitted to the Department of Pediatrics, University Hospital, Kuala Lumpur from January 1990 to December 1991. All patients with deterioriation in mental status showed a marked increase in liver enzymes (aspartate and alanine aminotransaminases) and severe coagulopathy. Six patients needed cerebral protection, including ventilation, intravenous sedation and muscle relaxants. There was one death during the period of study and one case of residual hemiparesis in a boy who had, in addition, intracerebral hemorrhage. All other survivors had complete recovery of liver and neurological function.

Dengue epidemic in the stage of Rio de Janeiro, Brazil, 1990-1: co-circulation of dengue 1 and dengue 2 serotypes.

Abstract: During 1990 and 1991, dengue fever was detected in the State of Rio de Janeiro, Brazil. It occurred in two epidemic waves; one, from January to August 1990, caused predominantly by dengue virus type 1 (DEN-1) the other from October 1990 to May 1991 caused by type 2 virus (DEN-2). Dengue was confirmed by virus isolation and/or IgM capture enzyme-linked immunosorbent assay (MAC-ELISA) in 2109/5964 (35.4%) of the cases. DEN-2 virus was isolated from 180 patients. HAI tests indicated that of these previous infection with DEN-1 had occurred in 130 (72%). The epidemic was classified as dengue fever, but severe and even fatal cases occurred in association with secondary infection.

Dengue in China: a clinical review.

Abstract: Three etiologically proven outbreaks of dengue fever and one etiologically confirmed epidemic of dengue haemorrhagic fever have occurred in south China since 1978. The first of these, an epidemic of dengue due to virus type 4 took place in Shiwan town, Foshan city, Guangdong Province, in 1978; the epidemic began in May and ended in November. The clinical manifestations of 583 hospitalized patients were observed from August to October. The majority (81.3%) of patients were aged 21-50 years (male:female = 1.2:1). The course of illness was about 1 week in most cases; three patients (0.5%) died. A local outbreak of dengue due to virus type 1 occurred in Shiqi town, Zhongshan County, Guangdong Province, from September to November 1979. The majority of patients were older children and adolescents. There was no marked difference between males and females in terms of the course of the illness, and there were no complications or deaths. A large epidemic of dengue due to virus type 3 occurred on Hainan Island in 1980. The clinical manifestations of 510 hospitalized patients (mostly adolescents and adults) were observed from April to September. Some patients developed rare complications, such as loss of hair, acute intravascular haemolysis, and multiple peripheral paralysis; there were four deaths (0.78%). The first known epidemic of dengue haemorrhagic fever in China occurred among 10-29-year-olds on Hainan Island in 1985 and 1986. There were no essential differences between males and females. Some cases had rare complications such as acute intravascular haemolysis, while others had diffuse intravascular coagulation and altered mental status; 10 patients (6.5%) died.

Congenital Yellow Fever Virus Infection after Immunization in Pregnancy

Abstract: To determine whether yellow fever (YF) vaccine administered in pregnancy causes fetal infection, women who were vaccinated during unrecognized pregnancy in a mass campaign in Trinidad were studied retrospectively. Maternal and cord or infant blood were tested for IgM and neutralizing antibodies to YF and dengue viruses. One of 41 infants had IgM and elevated neutralizing antibodies to YF virus, indicating congenital infection. The infant, the first reported case of YF virus infection after immunization in pregnancy, was delivered after an uncomplicated full-term pregnancy and appeared normal. Congenital dengue 1 infection may have occurred in another case. The frequency of fetal infection and adverse events after such exposure could not be estimated; however, the neurotropism of YF virus for the developing nervous system and the now documented possibility of transplacental infection underscores the admonition that YF vaccination in pregnancy should be avoided.

Molecular epidemiology of dengue 3 viruses and genetic relatedness among dengue 3 strains isolated from patients with mild or severe form of dengue fever in French Polynesia.

Abstract: The nucleotide sequences of a short fragment of the envelope protein gene encoding amino acids 25 to 89 of 27 dengue 3 viruses were determined by direct sequencing of PCR-amplified products, and the viruses were compared regarding their time of isolation and geographic distribution. Four distinct genotypic groups were discerned at 6% divergence between nucleotide sequences. The first group contained is olates from the South Pacific (1988 to 1992), Singapore (1973) and Indonesia (1973 to 1991). The second group comprised viruses from Asia (1956 to 1989) including the reference strain H-87. The third was composed of one isolate from Thailand (1971), and the fourth included the early strains from French Polynesia (1964 to 1969) and from Puerto Rico (1963). Furthermore, the difference between early and recent strains from the South Pacific was as high as 12.3%. This observation suggests that the recent epidemics in the South Pacific were probably the consequence of the spread of a new variant that emerged from New Caledonia. However, relatedness between nucleotide sequence and disease severity, or between strains from epidemics with mild disease (New Caledonia) and strains from epidemics with severe disease (French Polynesia) could not be demonstrated.

Dengue virus-specific human CD4+ T-lymphocyte responses in a recipient of an experimental live-attenuated dengue virus type 1 vaccine: bulk culture proliferation, clonal analysis, and precursor frequency determination.

Abstract: We analyzed the CD4+ T-lymphocyte responses to dengue, West Nile, and yellow fever viruses 4 months after immunization of a volunteer with an experimental live-attenuated dengue virus type 1 vaccine (DEN-1 45AZ5). We examined bulk culture proliferation to noninfectious antigens, determined the precursor frequency of specific CD4+ T cells by limiting dilution, and established and analyzed CD4+ T-cell clones. Bulk culture proliferation was predominantly dengue virus type 1 specific with a lesser degree of cross-reactive responses to other dengue virus serotypes, West Nile virus, and yellow fever virus. Precursor frequency determination by limiting dilution in the presence of noninfectious dengue virus antigens revealed a frequency of antigen-reactive cells of 1 in 1,686 peripheral blood mononuclear cells (PBMC) for dengue virus type 1, 1 in 9,870 PBMC for dengue virus type 3, 1 in 14,053 PBMC for dengue virus type 2, and 1 in 17,690 PBMC for dengue virus type 4. Seventeen CD4+ T-cell clones were then established by using infectious dengue virus type 1 as antigen. Two patterns of dengue virus specificity were found in these clones. Thirteen clones were dengue virus type 1 specific, and four clones recognized both dengue virus types 1 and 3. Analysis of human leukocyte antigen (HLA) restriction revealed that five clones are HLA-DRw52 restricted, one clone is HLA-DP3 restricted, and one clone is HLA-DP4 restricted. These results indicate that in this individual, the CD4+ T-lymphocyte responses to immunization with live-attenuated dengue virus type 1 vaccine are predominantly serotype specific and suggest that a multivalent vaccine may be necessary to elicit strong serotype-cross-reactive CD4+ T-lymphocyte responses in such individuals.

Ultra-rapid, simple, sensitive, and economical silica method for extraction of dengue viral RNA from clinical specimens and mosquitoes by reverse transcriptase-polymerase chain reaction

Abstract: A rapid, simple and efficient single-tube procedure is described for the isolation of dengue virus RNA from small amount of serum (10 microliters) followed by a reverse transcriptase-polymerase chain reaction (RT-PCR). Recovery of RNA is based on the lysing and nuclease-inactivating properties of guanidinium thiocyanate in the presence of silica. The silica RT-PCR can be completed within 5 hours starting from RNA extraction to agarose gel electrophoresis. All of the 63 dengue-3 culture-positive sera were RT-PCR-positive (virus titres: < 10(2) to 11(10.69.). Of 33 culture-negative acute sera from serologically confirmed dengue fever patients collected during dengue-3 epidemic, 4 were RT-PCR-positive. RT-PCR was also positive in 29 of 30 dengue-1 culture-positive sera (virus titres range: < 10(2) to 10(8.69). Dengue-1 virus was also detected in field-caught Aedes aegypti mosquitoes by silica RT-PCR.

Lessons of Aedes aegypti control in Thailand.

Abstract: . The incidence of dengue haemorrhagic fever (DHF) in Thailand has increased cyclically since the first recognized outbreak in 1958. Without an effective vaccine against dengue, and considering the clinical difficulty of treating DHF cases, vector control is needed to prevent dengue transmission. Since the establishment of the WHO Aedes Research Unit in 1964, continued since 1973 as the WHO Collaborating Centre at the Department of Medical Research in Bangkok, much operational research has been carried out in Thailand on the bionomics and control of dengue vectors: Aedes aegypti and Ae.albopictus. This review shows that, as in most other countries, dengue vector control programmes in Thailand make little use of the procedures arising from research, nor have they reduced the upward trend of dengue or prevented DHF outbreaks. Implications of the reluctance to use results of operational research on vector control are considered and remedial suggestions made.

Use of NS3 consensus primers for the polymerase chain reaction amplification and sequencing of dengue viruses and other flaviviruses.

Abstract: Consensus primers for the polymerase chain reaction were designed based on conserved motifs within the serine protease and RNA helicase domains encoded by the NS 3 genes of dengue and other flaviviruses. Target fragments of 470 bp were amplified on cDNA templates synthesized from RNAs of dengue types 1, 2, 3, and 4, Japanese encephalitis, Kunjin, and yellow fever viruses using random or specific downstream primers. PCR of oligo(dT)-primed cDNAs from Japanese encephalitis and Kunjin viral RNAs did not yield target bands. As few as 10(3) copies of dengue viral RNA could be detected. Direct DNA sequencing of PCR products of reference strains of dengue 2 (NGC), Kunjin (MRM 61C) and yellow fever (17 D) viruses demonstrated complete concurrence with published data. However, 2 nucleotide differences were observed between our data for dengue 3 H87 strain and the published sequence, resulting in a single amino acid disparity. Differences at 21, 16, and 11 nucleotide positions were noted between dengue 1 Hawaii and S 275/90; dengue 4 H 241 and 814669; Japanese encephalitis Nakayama and JaOArS 982 viral strains, culminating in only 4, 1 and 1 amino acid residue differences, respectively. These amino acid disparities occurred outside putative active sites of the enzymatic domains, emphasizing the important role of the NS3 protein in flaviviral replication. This RNA-PCR consensus primer strategy coupled with DNA sequencing represents a valuable tool for the molecular diagnosis and epidemiology of dengue and other flaviviral infections.

Dengue virus protein recognition by virus-specific murine CD8+ cytotoxic T lymphocytes.

Abstract: The identification of the protein targets for dengue virus-specific T lymphocytes may be useful for planning the development of subunit vaccines against dengue. We studied the recognition by murine dengue virus-specific major histocompatibility complex class I-restricted, CD8+ cytotoxic T lymphocytes (CTL) of dengue virus proteins using recombinant vaccinia viruses containing segments of the dengue virus genome. CTL from H-2k mice recognized a single serotype-cross-reactive epitope on the nonstructural (NS) protein NS3. CTL from H-2b mice recognized a serotype-cross-reactive epitope that was localized to NS4a or NS4b. CTL from H-2d mice recognized at least three epitopes: a serotype-specific epitope on one of the structural proteins, a serotype-cross-reactive epitope on NS3, and a serotype-cross-reactive epitope on NS1 or NS2a. Our findings demonstrate the limited recognition of dengue virus proteins by CTL from three inbred mouse strains and the predominance of CTL epitopes on dengue virus nonstructural proteins, particularly NS3. Since human dengue virus-specific CTL show similar patterns of recognition, these findings suggest that nonstructural proteins should be considered in designing vaccines against dengue.

Dengue: muscle biopsy findings in 15 patients

Abstract: Dengue is known to produce a syndrome involving muscles, tendons and joints. The hallmark of this syndrome is severe myalgia but includes fever, cutaneous rash, and headache. The neuromuscular aspects of this infection are outlined only in isolated reports, and the muscle histopathological features during myalgia have not been described. In order to ascertain the actual neuromuscular involvement in dengue and better comprehend the histological nature of myalgia, we performed a clinical and neurological evaluation, a serum CPK level and a muscle biopsy (with histochemistry) in 15 patients (4 males), median age 23 years (range 14-47) with classic dengue fever, serologically confirmed, during the bra-zilian dengue epidemics from September 1986 to March 1987. All patients had a history of fever, headache and severe myalgia. Upon examination 4 had a cutaneous rash, 3 had fever, and 3 a small hepatomegaly. The neurological examination was unremarkable in all and included a manual muscle test. CPK was mildly elevated in only 3 patients. Muscle biopsy revealed a light to moderate perivascular mononuclear infiltrate in 12 patients and lipid accumulation in 11. Mild mitochondrial proliferation was seen in 3, few central nuclei in 3, rare foci of myonecrosis in 3, and 2 patients had type grouping. Dengue in our patients, produced myalgia but no detectable muscle weakness or other neuromuscular involvement. The main histopathological correlation with myalgia seems to be a perivascular mononuclear infiltrate and lipid accumulation.

Seroepidemiology of dengue and other arboviruses in a natural population of toque macaques (Macaca sinica) at Polonnaruwa, Sri Lanka.

Abstract: A seroepidemiological study of arboviruses infecting 115 wild toque macaques (Macaca sinica) at Polonnaruwa, Sri Lanka showed a high prevalence of antibodies to dengue and Lumbo viruses. There was low seroprevalence of Chandipura (2/115) and Batai (1/115) virus antibodies, but no seropositivity to Chikungunya or Sindbis. There was no serological evidence of infection by Japanese encephalitis (JE) virus in spite of large human epidemics in the study area, indicating that toque macaques are unlikely to be an epidemiologically relevant host in the maintenance cycle of JE virus.

Vector competence of Aedes albopictus and Ae. aegypti (Diptera: Culicidae) to dengue 1 virus on Taiwan: development of the virus in orally and parenterally infected mosquitoes

Abstract: The vector competence in Ae. aegypti (L.) and Ae. albopictus (Skuse) from southern Taiwan to the dengue 1 virus was studied to elucidate the distribution of dengue infection during the 1987-1988 outbreak. The brain of Ae. aegypti was infected as early as 3 d after intrathoracic inoculation. The esophagus and the proboscis (tissues within the labium) were infected 5 d after inoculation. The salivary gland was highly susceptible to the virus, but no specific infection site was found. Gangli, muscles, and diverticula within the thorax were not infected. In the abdominal area, the ventral diverticula, Malpighian tubules, ganglia, and the dorsal vessel were not infected. However, the entire gut was susceptible to dengue 1 virus, although it was not infected simultaneously. Only a certain type of midgut epithelial cells was infected by the virus. The ovarioles, oviducts, and accessory glands frequently were infected. However, the spermathecae were not infected, perhaps because of the chitin-rich outer layer. Infections of the testes, vas deferens, seminal vesicles, and accessory glands of males also were detected in this study. The tissues of the proboscis were never infected in Ae. albopictus but frequently were infected in Ae. aegypti, indicating that the virus may escape the salivary gland barrier more efficiently in Ae. aegypti than in Ae. albopictus. When these mosquitoes were fed on hanging drops, the salivary gland infection and transmission rates of Ae. aegypti were always higher than those of Ae. albopictus. On Taiwan, Ae. aegypti appears to be a more competent vector in the transmission of the dengue 1 virus than Ae. albopictus.

Dengue epidemic in the state of Rio de Janeiro, Brazil: virological and epidemiological aspects

Abstract: Laboratory studies were carried out on 3178 patients with signs and symptoms suggestive of dengue infection from April 1986 to December 1987 in the State of Rio de Janeiro, Brazil. The epidemic had two peaks following the first virus isolation and affected the inhabitants of 17 counties. Both sex and all age groups were affected. Dengue virus type 1 was isolated from 1039 sera and the number of confirmed cases was increased to 1874 (59%) by MAC-ELISA. Isolation rate confirmed cases reached 80% in the specimens obtained until the 4th day after the onset of disease and viraemia ranged from 10(3.0) to 10(8.5) TCID50/ml.

Use of 'original antigenic sin' theory to determine the serotypes of previous dengue infections.

Abstract: Determination of serotypes of dengue viruses involved in sequential infections is important since, according to a theory of the pathogenesis of dengue haemorrhagic fever, a particular serotype may be a risk factor. It has been reported in Asia that at least the serotypes involved in the first infections could be serologically identified by the plaque reduction neutralization test (PRNT) because the highest PRNT titres after the second infections corresponded to the serotypes in the first infections. We re-examined the application of this theory of ‘original antigenic sin’ in Puerto Rico to evaluate its utility in serodiagnosis. Our results showed that it could not be applied reliably because of discrepant results.

Dengue Fever among Swedish Tourists

Abstract: Serologically confirmed cases of dengue fever among Swedish tourists were studied retrospectively. Dengue fever was found to be the most commonly diagnosed imported arbovirus disease in Sweden during the period December 1989 – November 1990. 24 cases were diagnosed. The geographical epidemiology showed that 17/23 who answered a questionnaire were infected in Thailand, most often during spring and early summer. 17 patients were admitted to hospital. All patients had high fever. Other common symptoms were myalgia, headache, fatigue/prostration and erythema. All patients but 1 with a long-standing ataxia recovered without sequelae. Low white blood cell and platelet counts were registered in all sampled patients. Depressed sodium levels and elevated liver enzymes were seen regularly. Dengue virus type 1 was isolated from 2 patients who suffered from dengue haemorrhagic fever grade II in the course of their primary dengue virus infection.

Dengue virus and endothelial cell: a related phenomenon to thrombocytopenia and granulocytopenia in dengue hemorrhagic fever.

Abstract: Adhesion to endothelial cells by blood cells was assessed by measuring the cell number of each blood cell component in the supernatant after exposing blood cells to dengue-infected endothelial cells for 0, 10, 20 and 30 minutes. White blood cells, neutrophils, lymphocytes, platelets, and large lymphocytes or large unstained cells (LUC) preferentially bound to dengue-infected endothelial cells as compared to the control endothelial cells. P values were 0.0096 for total leukocytes and platelets, 0.006 for lymphocytes, and 0.001 for neutrophils and LUC. Monocytes basophils and eosinophils had no interaction with dengue-infected endothelial cells. The increased binding of neutrophil and platelet to endothelial cell may explain neutropenia and thrombocytopenia in DHF patients.

Changes in levels of anti-dengue virus IgG subclasses in patients with disease of varying severity

Abstract: Extensive complement activation precedes onset of shock in dengue patients and complement "split products" C3a and C5a could be responsible, directly or indirectly, for the increased vascular permeability and disseminated intravascular coagulation which characterises dengue haemorrhagic fever (DHF) dengue shock syndrome (DSS). As IgG subclasses vary in their capacity to activate the classical complement pathway after combining with antigen, we have used an indirect enzyme linked immunosorbent assay (ELISA) to assess levels of IgG1-4 against each dengue serotype in acute and convalescent sera from patients with disease of varying severity. Acute phase sera from patients with dengue haemorrhagic fever (DHF) or dengue shock syndrome (DSS) contained higher levels of anti-dengue antibodies of the IgG1, complement fixing, subclass than similar sera from dengue fever (DF) patients. Conversely, acute phase sera from DHF and DSS patients contained lower levels of anti-dengue antibodies of the poor complement activating IgG2 subclass than acute phase sera from DF patients. No significant differences were detected between the levels of anti-dengue IgG3 and IgG4 antibody in acute phase sera from DF, DHF, and DSS patients. With the exception of levels of anti-dengue IgG2 antibody from DHF patients which were lower than those from DF and DSS patients, levels of anti-dengue IgG1, IgG2, IgG3, and IgG4 were similar in convalescent sera from all patients. These results provide a possible explanation for the activation of the serum complement system which precedes onset of shock in severe dengue infections.

Applications of polymerase chain reaction for identification of dengue viruses isolated from patient sera.

Abstract: A simple and sensitive procedure of reverse transcriptase polymerase chain reaction (RT-PCR) was developed previously such that all 4 serotypes of dengue viruses could be detected and their serotypes identified simultaneously in a single-step procedure. In this study we compared the RT-PCR with a conventional immunoperoxidase (PAP) staining method for the identification of dengue viruses currently isolated from patient sera. Sixty-six sera taken from dengue hemorrhagic fever (DHF) patients were subjected to virus isolation by inoculating onto C6/36 cell cultures. Screening for the presence of dengue viruses in culture fluids was done after 7 days of incubation by PAP staining using hyperimmune rabbit anti-dengue virus antibody as the primary reagent. Dengue viruses in positive cultures were further identified for their serotypes by PAP using type-specific monoclonal antibodies (MAb) and by RT-PCR. Thirty-two out of the 66 serum specimens tested (48.5%) were positive for dengue viruses. Of these, 5 were type 1 (DEN-1), 25 were type 2 (DEN-2) and 2 contained both DEN-1 and DEN-2. All cultures that were positive by PAP method were also positive by RT-PCR and vice versa. Thus, the results obtained by RT-PCR were in good agreement with those by PAP. It is important to point out that while all 5 DEN-1 isolates reacted readily with the MAb 1F1, only 2 of them could be identified by the MAb 15F3. Our data suggest that antigenic variation among DEN-1 isolates occur frequently and this should be taken into consideration in the selection of appropriate type-specific MAb for serotyping of dengue viruses. We also demonstrated dual infection of DEN-1 and DEN-2 in two patients' sera by RT-PCR.

Abnormal hemostasis in dengue hemorrhagic fever.

Abstract: . Abnormal hemostasis in dengue hemorrhagic fever includes:- 1. Vasculopathy which occurs during the early febrile to pre-shock and shock phase. The evidences support are: 1.1 Increased anaphylatoxin, released by complement activation causing leakage of intravascular fluid in to serous space. 1.2 Positive tourniquet test, some of which occur preceeding thrombocytopenia in the acute phase of DHF. 1.3 Excessive increased in PGI2 which is the most potent vasodilator and platelet aggregation inhibitor. 2. Platelets: 2.1 Thrombocytopenia due to 2.1.1 The bone marrow hypocellularity with increased in all forms of megakaryocytes but the vacuolated and disintegrated ones. 2.1.2 Destruction by the liver and spleen. 2.1.3 Immune-mediated injury as demonstration of dengue antibody complexes on the platelet surface. 2.1.4 The in vitro spontaneous aggregation to vascular endothelial cell pre-infected by dengue virus inducing platelet aggregation, causing lysis and platelet destruction. 2.2 Dysfunction shown by 2.2.1 Increased release of betathromboglobulin (BTG), PF4 and PGI2. 2.2.2 In vitro hypoaggregation stimulated by ADP and defect in ADP-releasing ability. 3. Coagulopathy including: 3.1 Prothrombin complex deficiency due to liver damage. 3.2 Consumptive coagulopathy due to the activation by mononuclear phagocytes, PF3 released from platelet aggregation. DIC is seen in prolonged shock cases of DSS.

Epidemic dengue 4 in the Yucatán, México, 1984

Abstract: An outbreak of dengue 4 occurred in the Yucatan, Mexico in 1984. During the course of the outbreak, 538 of 5486 reported cases of dengue-like illness were studied; 200 were confirmed as dengue serologically and/or virologically. Dengue 4 virus was isolated from 34 patients and dengue 1 from one. Severe haemorrhagic symptoms were observed in 9 laboratory confirmed patients, including four deaths. Thus, the outbreak in Yucatan is the second dengue epidemic in the Americas after the Cuban epidemic in 1981 in which a number of patients suffered from haemorrhagic complications. It was notable that 5 of 9 hospitalized, severe cases were young adults and that only one met the WHO criteria of DHF, in contrast to primary pediatric nature of DHF in Southeast Asia. In this paper we describe clinical, serologic, and virologic studies conducted during the outbreak.