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PubMed1992

Dengue activity in Puerto Rico, 1990.

Reported dengue activity in Puerto Rico (PR) increased in 1990 for the fourth consecutive year. The Community Hygiene Division of the PR Health Department received 9,540 reports of suspected dengue cases. Of the blood samples obtained from 7,660 patients, 1,911 were confirmed as dengue infection by laboratory tests at the Dengue Branch, San Juan Laboratories, Centers for Disease Control. Dengue 2 (DEN-2) continued to be the most frequently isolated serotype among all confirmed cases, hospitalized patients, and the confirmed cases with hemorrhagic manifestations. Disease was reported throughout the island and during all months, but activity, as in previous years, was lowest from April through July, and highest from September to November. The highest rates of laboratory-confirmed illness occurred in towns on the south coast and in the central mountains, with only one or two circulating virus serotypes (DEN-2 in the south; DEN-2 and DEN-4 in the central mountains). Although cases were confirmed in infants and octogenarians, the majority of laboratory-confirmed cases (1,293, 68%), and the highest attack rates (0.70/1000), were reported in persons younger than 30. Of patients with confirmed cases, 289 (15%) were hospitalized, and 438 (23%) reported at least one hemorrhagic manifestation. One presumptive dengue case with fatal outcome was reported in 1990 in a 17-year-old woman in whom a febrile illness, seizures, and coma developed; she died after cardiorespiratory arrest. Recent dengue infection in this individual was serologically documented, but no virus was isolated.

Adolescent↗
PubMed2005

Evaluation of the present dengue situation and control strategies against Aedes aegypti in Cebu City, Philippines.

The present dengue situation and methods to control Aedes aegypti larvae in Cebu City, Philippines, were evaluated for the development of an integrated community-based dengue control program. The study included the detection of dengue infection among Filipino patients, surveying mosquito breeding sites to determine larval population density of Aedes aegypti, an evaluation of public knowledge, attitude, and personal protection practices against dengue, and an evaluation of the efficacy of VectoBac DT/Culinex Tab tablets based on Bacillus thuringiensis israelensis against Ae. aegypti larvae. Of the 173 human sera samples that were assayed for dengue viruses, 94.9% were positive, 2.2% negative and 2.8% equivocal. Thirty households were randomly chosen per Barangay "Villages" (lowest level of formal local administration). Of the 489 breeding sites surveyed, 29.4% were infested with Ae. aegypti larvae, with discarded tires having the highest infestation rate (69.4%). A survey of people's knowledge, attitude, and practices for integrated community-based dengue control showed that 68.7% of the interviewees were aware that dengue is transmitted by mosquitoes, but only 4.3% knew that a virus was the cause of the disease. The efficacy of one and two tablets of VectoBac DT/Culinex Tab, based on Bacillus thuringiensis israelensis, was assessed against the larvae of Ae. aegypti exposed to sunshine and shaded water containers in semi-field and field tests. In semi-field tests, 100% mortality was achieved until the 18th and 30th day after the application of one and two tablets, respectively, in sun-exposed containers. In shaded containers, 100% mortality was observed until the 30th and 36th day after the application of one and two tablets, respectively. In field tests, the tablets were effective for approximately 3 weeks.

Aedes↗
PubMed1989

[Serological and virological diagnosis for dengue infection].

For many years dengue fever has been one of the most serious diseases in southeast Asia. A dengue type 2 epidemic occurred in Liuchiu, Pingtung in 1981. A recent epidemic, primarily of dengue type 1 has been in progress in southern Taiwan since 1987. In clinical aspects, dengue infection may be confused with measles, rubella, influenza, acute mumps, enteric viral infection and food allergies. Only definite confirmation is possible through serological and virological methods. All four serotypes of the dengue virus, however, are antigenically similar, and their antibodies are also cross-reactive with other flaviviruses. This phenomenom renders the specificity of many serological tests to be less accurate than they should be. Thus, improved virus isolation and identification becomes a necessary tool in proving the dengue infection. This article offers a brief review of some serological tests including the hemagglutination inhibition test, IgG- and MAC-ELISA, the plaque reduction neutralization test, and virological tests including antigen capture ELISA and indirect immunofluorescence antibody assay, with emphasis on their application to the diagnosis of dengue infection.

Antibodies, Viral↗
PubMed1987

Studies into the immunopathogenesis and laboratory diagnosis of dengue haemorrhagic fever.

Studies were carried out into the immunopathogenesis and laboratory diagnosis of dengue virus infections. Using an experimental system it was shown that cell-mediated immunity (CMI), as measured by delayed-type hypersensitivity (DTH) was induced in mice infected with dengue virus. The nature of the DTH response satisfies most criteria for a classical DTH reaction. In addition, it was also shown that infection with dengue virus causes a transient immunosuppression as measured by the immune response to other, unrelated antigens. With regard to the laboratory diagnosis of dengue infections, it was found that mosquito cells were a sensitive system for the isolation of dengue viruses and that the success of isolation was related to the antibody content of the serum. A new method for the rapid isolation of dengue viruses was also developed involving the intracerebral inoculation of mosquito larvae. By the use of this method viral antigens can be detected as early as 2-3 days after specimen inoculation. The significance of these findings in relation to the immunopathogenesis, prevention and control of disease syndromes due to dengue viruses is discussed.

Animals↗
PubMed1973

Pathogenetic mechanisms in dengue haemorrhagic fever: report of an international collaborative study.

In a study of 55 persons with dengue haemorrhagic fever-36 of whom showed the dengue shock syndrome-clinical, haematological, virological, and serological changes were correlated with serial measurements of complement components and immunopathological studies. Viruses dengue-1 or dengue-2 were isolated from the sera of 9 patients. Serological responses indicative of secondary dengue virus infections were observed in 53 patients; 2 (infants) had primary infections. During the acute phase of the disease, dengue antibody titres rose logarithmically. Marked depression of complement components, especially C3, was observed. Activation of both the classical and alternative complement pathways was demonstrated, with depression of both C4 and C3 proactivator levels in most instances, although in some cases it appeared that one mechanism was involved to a greater extent than the other. The level of depression of C3 was correlated with the severity of the disease. Relatively stable transferrin levels indicated that depletion of complement proteins was not primarily due to extravasation. Fibrinogen levels were depressed and fibrinogen split products were found in the plasma. The accumulated data provide further evidence of the central role that activated complement components play in the pathogenesis of dengue haemorrhagic fever.

Blood Coagulation Tests↗
PubMed1971

Aedes aegypti (L.) and Aedes albopictus (Skuse) in Singapore City. 5. Observations in relation to dengue haemorrhagic fever.

Dengue haemorrhagic fever in Singapore was a disease of the urban human population, with concentrations of cases occurring in areas of high population density. Mosquito surveys revealed that these areas also had high population densities of Ae. aegypti and Ae. albopictus.The disease occurred throughout the year but the incidence of cases appeared to follow a seasonal pattern. Observations from 1966 to 1968 showed that the number of cases increased in April, reached a peak in November, and, thereafter, decreased until the next increase in April of the following year. The epidemic curve generally agreed with the fluctuations of both Ae. aegypti and Ae. albopictus populations, although the latter species appeared to show a better correspondence with the incidence of cases.Six dengue viruses were isolated from the two Aedes species during 1966. One dengue type 2 virus was isolated from a pool of Ae. aegypti and 1 dengue type 1 virus and 4 dengue type 2 viruses were recovered from 5 pools of Ae. albopictus. These viruses were isolated from mosquitos collected during the period of increase in the incidence of cases and in 4 different areas of the city. The dengue virus infection rates per 1 000 mosquitos estimated in the present study were 0.51 for Ae. aegypti and 0.59 for Ae. albopictus.The data obtained in the present study suggest that both Ae. aegypti and Ae. albopictus are involved in the transmission of dengue haemorrhagic fever in Singapore.

Aedes↗
PubMed1983

Serological studies on volunteers inoculated experimentally with a dengue virus strain in 1943.

In 1943, a large dengue epidemic occurred in the Osaka district and several samples of dengue virus were isolated from patients with dengue fever by workers in this Institute. These were inoculated into human volunteers to confirm that they were dengue virus. In the present study, serum samples were collected from the volunteers who had been inoculated with dengue virus and were examined serologically. In the neutralization test, all the sera showed a higher titer against dengue type 1 virus (DEN-1) than against the other three types of dengue virus, indicating that the virus strain isolated in 1943 was DEN-1.

Antibodies, Viral↗
PubMed1995

Dengue type 3 infection--Nicaragua and Panama, October-November 1994.

The geographic range and incidence of dengue virus activity in the Americas substantially increased from 1980 to 1994. During this period, all dengue activity in the Americas was associated with dengue serotypes 1, 2, and 4 (DEN-1, DEN-2, and DEN-4). On November 25, 1994, the Ministry of Health of Nicaragua announced the isolation of dengue type 3 (DEN-3) from two children hospitalized with minor hemorrhagic manifestations in Managua. Subsequently, DEN-3 virus was isolated from two persons with dengue fever in Panama. These cases represent the first isolation of DEN-3 from autochthonous cases in the Americas since 1977. This report describes these cases and dengue activity in Nicaragua and Panama and summarizes public health activities to control dengue fever in the Americas.

Child, Preschool↗
PubMed1994

Do Ross River and dengue viruses pose a threat to New Zealand?

AIM: To determine the prevalence of antibodies to Ross River and dengue viruses in sera from New Zealand residents and travellers and to assess the potential of local mosquitoes to act as vectors of these viruses. METHOD: Serum specimens from several population groups were examined by haemagglutination-inhibition and neutralisation tests for antibodies to Ross River and dengue viruses between 1975 and 1993. During this period dengue was active in South East Asia, Australia and the Pacific, and a major epidemic of Ross River infection occurred in the Pacific. Two New Zealand mosquito species were tested for their ability to transmit by bite after they had been fed or injected with these viruses. RESULTS: Ten percent of 1869 sera from patients suspected of contracting dengue, and 43% of 183 patients suspected of contracting Ross River virus, while overseas, were antibody positive. Many patients showed antibody rises which indicated that they were probably viraemic on entry to this country. Dengue viruses were isolated in Dunedin from two patients with dengue haemorrhagic fever contracted overseas. Antibody studies of persons who had not travelled outside New Zealand provided no evidence of local transmission of these viruses. Two local mosquitoes, Aedes notoscriptus from the Auckland area, and Aedes australis from the Otago area, were able to transmit one or both these viruses under laboratory conditions. CONCLUSIONS: The serological studies showed that both Ross River and dengue viruses have probably been introduced into New Zealand by viraemic travellers on many occasions. Although some local mosquitoes can transmit these viruses in the laboratory, there is no evidence of local spread of virus from these imported cases. Changing environmental conditions such as global warming with concomitant effects on vector distribution, increasingly rapid air travel by viraemic persons and the accidental introduction of new vector mosquitoes, particularly Aedes albopictus, could pose a threat in view of the high percentage of New Zealand residents with no protective antibody.

Aedes↗
PubMed1997

Hemorrhagic fever in Cambodia is caused by dengue viruses: evidence for transmission of all four serotypes.

Hemorrhagic fever (HF) has been widespread in Cambodia and thought to be due to dengue virus although laboratory confirmation has been lacking. Between 1980 and 1995, 49,420 cases of HF and 3,032 deaths were reported. Cases increased during this period; large epidemics of HF occurred every two to three years. In 1995 there were 10,208 cases of HF with 424 deaths. Over a two day period in August 1995, 40 consecutive cases were investigated at the National Pediatric Hospital in Phnom Penh, Cambodia. All 40 cases were confirmed as dengue by virus identification and/or serology. Mean age was 6.5 years. Of 39 patients with complete medical records, the diagnoses were: dengue fever (n = 3), dengue hemorrhagic fever (DHF) grade 2 (n = 21), DHF grade 3 (n = 10), and DHF grade 4 (n = 5). The serologic response was secondary in 95%. Dengue virus was identified in 13 of 40 cases. All four dengue serotypes were identified. The high frequency of secondary infections, the low mean age of admission, and identification of all four dengue serotypes support the national statistics to show that DHF is highly endemic in Cambodia.

Adolescent↗
PubMed1997

Molecular diagnosis and epidemiology of dengue virus infection.

Early diagnosis of dengue fever contributes towards appropriate management of the disease and its potentially severe complications. Better and more rapid molecular procedures are increasingly available for detecting dengue viral RNA, antibodies and antigens. Using consensus primers based on the conserved non-structural-3 gene, the reverse transcription-polymerase chain reaction (RT-PCR) technique can amplify all four dengue virus types as well as certain flaviviruses. Consensus primers used together with four type-specific downstream primers in single-step or semi-nested RT-PCR formats can discriminate the specific dengue virus type by virtue of the diagnostic size of the RT-PCR target fragment on agarose gel electrophoresis. Alternatively, RT-PCR products may be labelled with digoxigenin and allowed to hybridise with individual biotinylated type-specific PCR primers which act as capture probes immobilised on solid phase via streptavidin-coated tubes. With automated instrumentation for enzyme-linked immunosorbent assay (ELISA), the hybridised RT-PCR products can be quantitated spectrophotometrically via anti-digoxigenin antibodies conjugated with an enzyme which reacts with colourimetric substrate. While RT-PCR is highly sensitive, specific and successfully identifies the dengue virus type in clinical serum samples and adult Aedes mosquitoes, it generally yields positive results in viraemic sera collected within 2 to 5 days of pyrexia. Sera obtained after the period of viraemia are more likely to be positive by serological tests such as IgM capture ELISA or the commercial Dengue Blot kit. The RT-PCR primers can also be utilised for direct cycle dideoxy DNA sequencing to monitor the molecular epidemiology and evolution of geographically and temporally separated virus strains. To exemplify this, nucleotide and amino acid sequence data as well as phylogenetic trees of several strains of dengue 1 and 2 viruses from patients and field-caught Aedes mosquitoes are presented.

Base Sequence↗
PubMed1995

Antibodies that block virus attachment to Vero cells are a major component of the human neutralizing antibody response against dengue virus type 2.

Epidemiological data strongly implicate a role for the host humoral immune response in both protection against and exacerbation of dengue virus-caused disease. In an effort to characterize elements of the normal human immune response against dengue virus we have addressed the issue of antibody-mediated neutralization of dengue virus. We show here the ability of both mouse monoclonal antibody 3H5 and human anti-dengue neutralizing sera to block binding of dengue-2 virus to monkey kidney (Vero) cells. Since Vero cells possess virus receptors but not Fc receptors we conclude that the major effect of host neutralizing antibodies is to block virus attachment to Vero cell dengue virus receptors. Analysis of 61 patient antisera yielded good correlation (Pearson's coefficient = 0.90; P < 0.001) between neutralizing activity and ability to block virus-cell attachment suggesting that antibody-mediated neutralization of dengue virus occurs primarily extracellularly and less by a postattachment mechanism as has been described for certain other viruses.

Adolescent↗
PubMed1995

Cytotoxic factors released by dengue virus-infected human blood monocytes.

Human monocyte-derived cytotoxic factors (CF) induced by dengue virus were studied. Using several human leukemia cell lines as precursors, the biological activities of CF in conditioned medium from dengue virus-infected monocytes were demonstrated through the measurement of tumor cell growth inhibition. The conditioned medium from dengue virus infected monocytes suppressed significantly growth of CEM, HL60, K562, and U937 cells. In the presence of 10% conditioned medium (v/v) from dengue virus infected monocytes, DNA synthesis of U937 cells, as measured by [3H]thymidine incorporation, decreased by 99% in contrast to their synthesis in conditioned medium from noninfected control monocytes, which did not have any suppressive effect. Partial characterization of CF showed that it is a proteinase-K-sensitive and heat-labile protein with a molecular mass over 100 kDa. Employing a flow cytometric analysis of the cell cycle, it was found that U937 cells, treated either with conditioned medium from dengue virus infected monocytes or with CF, but not treated with conditioned medium from noninfected monocytes, showed cell-cycle arrest in G1 phase by 48 hr. This suppressive effect of CF on U937 growth was dose- and time-dependent. These results suggest that dengue virus-infected monocytes may produce CF to target myeloid cells, resulting in the hematological changes observed in patients with dengue fever.

Adult↗
PubMed1988

Nucleotide sequence of dengue 2 RNA and comparison of the encoded proteins with those of other flaviviruses.

We have determined the complete sequence of the RNA of dengue 2 virus (S1 candidate vaccine strain derived from the PR-159 isolate) with the exception of about 15 nucleotides at the 5' end. The genome organization is the same as that deduced earlier for other flaviviruses and the amino acid sequences of the encoded dengue 2 proteins show striking homology to those of other flaviviruses. The overall amino acid sequence similarity between dengue 2 and yellow fever virus is 44.7%, whereas that between dengue 2 and West Nile virus is 50.7%. These viruses represent three different serological subgroups of mosquito-borne flaviviruses. Comparison of the amino acid sequences shows that amino acid sequence homology is not uniformly distributed among the proteins; highest homology is found in some domains of nonstructural protein NS5 and lowest homology in the hydrophobic polypeptides ns2a and 2b. In general the structural proteins are less well conserved than the nonstructural proteins. Hydrophobicity profiles, however, are remarkably similar throughout the translated region. Comparison of the dengue 2 PR-159 sequence to partial sequence data from dengue 4 and another strain of dengue 2 virus reveals amino acid sequence homologies of about 64 and 96%, respectively, in the structural protein region. Thus as a general rule for flaviviruses examined to date, members of different serological subgroups demonstrate 50% or less amino acid sequence homology, members of the same subgroup average 65-75% homology, and strains of the same virus demonstrate greater than 95% amino acid sequence similarity.

Amino Acid Sequence↗
PubMed1988

Nucleotide sequence and deduced amino acid sequence of the nonstructural proteins of dengue type 2 virus, Jamaica genotype: comparative analysis of the full-length genome.

The sequence of the 5'-end of the genome of dengue 2 (Jamaica genotype) virus has been previously reported (V. Deubel, R. M. Kinney, and D. W. Trent, 1986, Virology 155, 365-377). We have now cloned and sequenced the remaining 75% of the genomic RNA that encodes the nonstructural proteins. The complete genome is 10,723 bases in length with a single open reading frame extending from nucleotides 97 to 10,269 encoding 3391 amino acids. The 3'-noncoding extremity presents a stem- and loop-structure and contains a repeated oligonucleotide sequence. Comparisons of the nucleotide sequences of the genomes of dengue 2 viruses of different topotypes reveal 90-95% similarity, with 64-66% similarity evident between dengue viruses of different serotypes. The amino acid sequence of the polyprotein of dengue 2 Jamaica virus shows 97, 68, 50, and 44% similarity with those of other dengue 2, dengue 1, or dengue 4, West Nile, and yellow fever viruses, respectively. Despite amino acid sequence divergence, the hydrophobic profile of the flavivirus proteins is highly conserved. Proteins NS1, NS3, and NS5 are the most conserved. Conserved amino acid stretches present in all flavivirus proteins may be involved in common essential biological functions.

Amino Acid Sequence↗
PubMed1993

Identification of helper T cell epitopes of dengue virus E-protein.

The T cell proliferative response to dengue 2 (Jamaica) E-glycoprotein (495 amino acids) was analyzed in vitro using either killed virus or E-protein fragments or synthetic peptides. Inactivated dengue virus stimulated dengue-specific lymph node (LN) CD4+T cell proliferation in BALB/c (H-2d), C3H (H-2k) and DBA/1 (H-2q) but not in C57BL/6 (H-2b) mice. Moreover, LN cells from dengue-virus primed BALB/c mice proliferated in vitro in response to three purified non-overlapping E-protein fragments expressed in E. coli as polypeptides fused to trpE (f22-205, f267-354, f366-424). To further determine T cell epitopes in the E-protein, synthetic peptides were selected using prediction algorithms for T cell epitopes. Highest proliferative responses were obtained after in vitro exposure of virus-primed LN cells to peptides p135-157, p270-298, p295-307 and p337-359. Peptide p59-78 was able to induce specific B and T cell responses in peptide-primed mice of H-2d, H-2q and H-2k haplotypes. Two peptides p59-78 corresponding to two dengue (Jamaica and Sri Lanka) isolates and differing only at position 71 cross-reacted at the B but not at the T cell level in H-2b mice. This analysis of murine T helper cell response to dengue E-protein may be of use in dengue subunit vaccine design.

Amino Acid Sequence↗
PubMed2005

[An epidemic of dengue fever in a department of paediatrics: report on 58 cases in Lamentin (Martinique)].

UNLABELLED: Dengue fever is caused by a virus transmitted by an Aedes mosquito, and infects 80 million people in the world annually. 30 000 case fatality of Dengue hemorrhagic fever are estimated each year. The disease, endemo-epidemic in the inter-tropical area, is a public health problem. PATIENTS AND METHODS: An epidemic of dengue fever occurred in Martinique, French department of the Caribbean, in 2001-2002. This work was a clinical and epidemiologic study of dengue and dengue hemorrhagic fever in 58 children. RESULTS: Three children (5%) developed a hemorrhagic dengue, and 13 subjects (24%) presented at least with one hemorrhagic sign. Symptoms were polymorphous, certain forms were only myalgic; the main reason for consultation was the fever (89%). The principal characteristics were a leucopenia (56%) associated with a neutropenia (80%), a thrombocytopenia (54%), a hepatic cytolysis (66%) and sometimes a muscular cytolysis (9/15) and a increase in the ferritinemia (16/27). No death was noted. CONCLUSION: The treatment of the dengue is above all preventive, it consists in the antivector fight.

Adolescent↗
PubMed2004

Classic dengue fever affects levels of circulating antioxidants.

OBJECTIVE: We studied alterations of circulating antioxidant nutrients in patients with classic dengue fever in the tropical lowlands of Guatemala. METHODS: In nine patients with dengue fever and 12 healthy Guatemalan control subjects, we assessed plasma concentrations of retinol, alpha-tocopherol, beta-carotene, glutathione, taurine, thiobarbituric acid-reactive species, and total antioxidant status. Control subjects were assessed twice within 48 h to account for day-to-day variations. Febrile patients with dengue fever were examined on the day of admission to the hospital, at discharge after defervescence (approximately 5 d after admission), and 7 d thereafter. RESULTS: In patients with dengue fever, increases in plasma concentrations of retinol and beta-carotene were seen, whereas decreases were observed for glutathione and total antioxidant status. As compared with the reference group, patients with dengue fever had lower retinol concentrations in the acute phase of the disease and lower glutathione concentrations 7 d after discharge. Further, thiobarbituric acid-reactive species levels were higher in the dengue fever patients as analyzed by unpaired t test. CONCLUSION: Using dengue fever as a model for the metabolic response to an acute, self-limited tropical viral infection, the present findings suggest slight turbulence of the antioxidant system that may be a response to or a consequence of the viral inflammatory process.

Adult↗