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PubMed2004

Analysis of specific IgM responses in secondary dengue virus infections: levels and positive rates in comparison with primary infections.

BACKGROUND: Dengue viruses are a serious cause of illness in tropical and subtropical areas of the world. Laboratory diagnosis is essential for confirmation of dengue virus infections. Detection of specific IgM by IgM-capture enzymed-linked immunoassay (ELISA) has been widely used as a main serological diagnostic technique. OBJECTIVES: The levels of specific IgM in secondary dengue virus infections were compared with those in primary infections. STUDY DESIGN: A total of 1780 samples collected from 924 confirmed dengue cases were tested for anti-dengue IgM by IgM-capture ELISA. RESULTS AND CONCLUSIONS: Specific IgM was detected in all the cases with primary dengue virus infection on disease day 9 or later. However, specific IgM cannot be detected in 28% (204/716) of the cases in secondary infections. The average titers of IgM were higher in primary infections than in secondary infections. The results confirmed that IgM detection is a reliable serological diagnostic test in primary dengue virus infections. Although IgM detection is also a useful test, other serological diagnostic tests or tests for dengue virus detection are necessary for confirmation of all the secondary dengue virus infections.

Acute Disease↗
PubMed2005

An outbreak of primary dengue infection among migrant Chinese workers in Singapore characterized by prominent gastrointestinal symptoms and a high proportion of symptomatic cases.

BACKGROUND: An outbreak of dengue occurred among Chinese migrant workers at a construction site in Singapore that was characterized by a number of unusual features. METHODS: Clinical and laboratory data were prospectively collected from workers who were hospitalized with fever. We compared the frequency of disease manifestations in these patients with historical data from other cases of dengue admitted to the same centre. A serological survey was performed at the construction site one month after the onset of the outbreak. RESULTS: Thirty-nine patients were admitted from the affected construction site with confirmed acute dengue infection in March and April 2002. Fever, headache and rash were common and occurred at similar frequency in outbreak patients and historical controls. Gastrointestinal manifestations were significantly more common in the outbreak patients compared with controls (nausea 68%, diarrhea 41%, hyponatremia 47% and elevated urea 20%). Of the 274 studied in the serological survey, 27 had serological evidence of acute dengue, of whom 24 (89%) had experienced a febrile illness in the previous month. The virus was cultured and identified as Dengue-2. Few patients had a positive IgG for dengue indicating that this was likely a primary infection. CONCLUSION: This outbreak of primary dengue infection was characterized by unusually prominent gastrointestinal symptoms and a high proportion of symptomatic transmission. Manifestations of dengue may be altered when outbreaks involve immunologically naïve adults who have migrated to dengue endemic areas.

Adult↗
PubMed2006

Laboratory surveillance of dengue virus in Central Brazil, 1994-2003.

BACKGROUND: In Brazil, dengue endemic and epidemic patterns indicate an upward trend in incidence and hospitalization in the past decade. OBJECTIVE: To report dengue circulating serotypes from 1994 to 2003 and the role of distinct serotypes on dengue clinical outcomes in Central Brazil. METHODS: Virological surveillance for dengue cases was conducted in the city of Goiania ( approximately 1,200,000 population) from 1994 to 2003. Samples were tested using dengue IgM antibody (MAC-ELISA) and/or virus isolation. Circulating subtypes and genotypes were identified by reverse transcriptase PCR (RT-PCR) and by restricted site-specific PCR (RSS-PCR) patterns in selected samples. RESULTS: Adults (87.4%) were the most affected group and dengue fever accounted for the majority of the cases. Laboratory surveillance identified mainly DEN 1 serotype from 1994 to 2002 shifting to a high circulation of DEN 3 in 2003. The ratio of dengue fever to dengue with complications/DHF remained constant following the introduction of DEN 3. Diagnosis of dengue was confirmed in approximately 50% of the suspected cases enhanced by RT-PCR. RSS-PCR patterns for DEN 1 and DEN 3 corresponded to the circulating subtypes in the country. CONCLUSIONS: The result of virological surveillance did not suggest a major role of infecting DEN 3 serotype in increasing disease severity during its first-year spread in Central Brazil.

Adolescent↗
PubMed2005

A custom-designed recombinant multiepitope protein as a dengue diagnostic reagent.

Currently, dengue fever is the most important re-emerging mosquito-borne viral disease, with the major proportion of the target population residing in the developing countries of the world. In endemic areas, potentially fatal secondary dengue infections, characterized by high anti-dengue IgG antibody titers, are most common. Most currently available commercial dengue diagnostic kits rely on the use of whole virus antigens and are consequently associated with false positives due to serologic cross-reactivity, high cost of antigen production, and biohazard risk. This has prompted the need to develop an alternate antigen to replace the whole virus antigen in diagnostic tests. We have designed and expressed a novel recombinant protein antigen by assembling key immunodominant linear IgG-specific dengue virus epitopes, chosen on the basis of pepscan analysis, phage display, and computer predictions. The recombinant dengue multiepitope protein was expressed to high levels in Escherichia coli, purified in a single step, yielding >25 mg pure protein per liter culture. We developed an in-house enzyme-linked immunosorbent assay (ELISA) to detect anti-dengue antibodies in a panel of 20 patient sera using the purified recombinant dengue multiepitope protein as the capture antigen. The ELISA results were in excellent agreement with those obtained using a commercially available diagnostic test, Dengue Duo rapid strip test from PanBio, Australia. The high epitope density, careful choice of epitopes, and the use of E. coli system for expression, coupled to simple purification, jointly have the potential to lead to the development of an inexpensive diagnostic test with a high degree of sensitivity and specificity.

Amino Acid Sequence↗
PubMed2005

Dengue virus: molecular basis of cell entry and pathogenesis, 25-27 June 2003, Vienna, Austria.

Multivalent dengue vaccines now in late stage development pose unique vaccine safety challenges in that primary or secondary vaccine failures might place vaccines at risk to antibody-dependent enhanced (ADE) wild-type dengue infections. This conference was organized to address this unique vaccine safety issue. New data were presented on the structure of dengue and other flaviviruses, the cellular receptors of dengue virus for biologically relevant cells, dengue viral cell entry mechanisms and mechanisms underlying in vivo protection, neutralization and enhancement of dengue virus infection. It was concluded that a targeted research program should aim to develop an in vitro test to characterize persons immunized with dengue vaccines as completely or partially protected. Achievement of this aim will require a better understanding of the basic mechanisms by which dengue viruses recognize, attach, enter and infect relevant human cells and how antibodies protect against dengue infections.

Antibodies, Viral↗
PubMed1998

Evaluation of molecular strategies to develop a live dengue vaccine.

BACKGROUND: Millions of individuals are estimated to become infected with dengue virus each year, particularly in tropical and subtropical regions. Mortality is low but infection can lead to a severe form of dengue, characterised by haemorrhage and shock. A safe and effective vaccine against dengue is still not available. OBJECTIVE: To use the successful construction of dengue type 4 virus (DEN4) cDNA, which yields infectious RNA transcripts, to provide a new approach to the development of safe and effective dengue vaccines. STUDY DESIGN: The 3' and 5' noncoding (NC) regions of the genome were targeted to construct DEN4 deletion mutants, because the sequences in these regions are thought to play an important role in the regulation of viral replication. DEN4 cDNA was also employed to construct a viable chimeric virus with dengue type 1, 2 or 3 antigenicity, by substitution of heterotypic structural protein genes. RESULTS: Most viable mutants, recovered from the cDNA constructs, were partially restricted for growth in simian cells as analysed by plaque morphology assay and viral yield analysis. Several 3' NC deletion mutants which exhibited a range of growth restriction in cell culture were further evaluated for infectivity and immunogenicity in rhesus monkeys. Occurrence and duration of viraemia were reduced for these deletion mutants, compared to the wild type DEN4. Analysis of antibody response to infection in rhesus monkeys also indicated that some of these mutants were attenuated. These DEN4 deletion mutants represent promising live dengue vaccine candidates that merit further clinical evaluation. Chimera DEN1/DEN4 or DEN2/DEN4 which expresses DEN1 or DEN2 antigenicity were also used to infect monkeys. Most monkeys immunised with these chimeric viruses, singly or in combination, developed high titres of neutralising antibodies and were protected against homotypic wild type DEN1 or DEN2 challenge. CONCLUSIONS: DEN4 and its derived chimeric viruses of other three dengue serotype specificity, that contain appropriate attenuating mutations, have a potential use in a tetravalent live vaccine against dengue.

Animals↗
PubMed2002

Long-term memory cellular immune response to dengue virus after a natural primary infection.

OBJECTIVES: This study was conducted to examine the memory T-cell response to dengue virus 20 years after a primary infection. We took advantage of the exceptional epidemiologic situation in Cuba, where the population initially suffered two large successive epidemics due to dengue virus 1 and 2 respectively over a 4-year period. Thereafter, no dengue virus circulation was subsequently observed, except for the Santiago de Cuba municipality. DESIGN: T-cell response was evaluated in peripheral blood mononuclear cells (PBMCs) from 20 individuals with history of a primary infection by dengue virus 1 or 2. Methods previously shown to induce lymphoproliferation of CD4+ memory T-cell subpopulations were used. We evaluated the proliferative responses generated in those PBMCs after stimulation with dengue virus 1, 2, 3 and 4 antigens in a serotype-specific and serotype-crossreactive way. RESULTS: Serotype-specific and serotype-crossreactive lymphoproliferative responses in all PBMCs donated by dengue immune donors were observed. The serotype-crossreactive response for dengue 2 was stronger than for the rest of the serotypes. CONCLUSIONS: This is the first report of cellular memory lymphocyte response specific for dengue virus detected 20 years after a primary infection by dengue.

Adult↗
PubMedDate not supplied

Expansion of epidemic dengue viral infections to Pakistan.

OBJECTIVES: Antibodies to dengue viruses have occasionally been reported in individuals in Pakistan, but the frequency of occurrence of dengue infection in Pakistan is unclear. The first confirmed dengue hemorrhagic fever outbreak in Pakistan occurred in 1994. In October 1995, the authors investigated an outbreak of a febrile illness among employees of a construction contractor at a power generation plant in Baluchistan, Pakistan, to determine the cause of illness and recommend appropriate preventive measures. METHODS: The work site and living arrangements were inspected, a questionnaire was administered, and serum samples were collected from all consenting contractor employees and their families if they lived at the camp. Sera were analyzed for IgM against dengue virus, using an enzyme-linked immunosorbent assay. RESULTS: Interviews were conducted with 76 persons (mean age, 42y); 95% were men. Forty-two persons (55%) reported having experienced fever, headache, or myalgia in the preceding 6 weeks. Fifty-seven subjects (75%) had IgM antibodies against at least one dengue serotype; 45 subjects (59%) had IgM antibodies against dengue serotype 2. CONCLUSION: This was an outbreak of dengue fever due to multiple serotypes of dengue virus. This confirms that epidemic dengue infection was present in southern Pakistan for 2 consecutive years.

Adult↗
PubMed2002

Evaluation of the World Health Organization standard tourniquet test and a modified tourniquet test in the diagnosis of dengue infection in Viet Nam.

OBJECTIVES: A positive tourniquet test is one of several clinical parameters considered by the World Health Organization to be important in the diagnosis of dengue haemorrhagic fever, but no formal evaluation of the test has been undertaken. As many doctors remain unconvinced of its usefulness, this study was designed to assess the diagnostic utility of both the standard test and a commonly employed modified test. METHODS: A prospective evaluation of the standard sphygmomanometer cuff tourniquet test, compared with a simple elastic cuff tourniquet test, was carried out in 1136 children with suspected dengue infection admitted to a provincial paediatric hospital in southern Viet Nam. RESULTS: There was good agreement between independent observers for both techniques, but the sphygmomanometer method resulted in consistently greater numbers of petechiae. This standard method had a sensitivity of 41.6% for dengue infection, with a specificity of 94.4%, positive predictive value of 98.3% and negative predictive value of 17.3%. The test differentiated poorly between dengue haemorrhagic fever (45% positive) and dengue fever (38% positive). The simple elastic tourniquet was less sensitive than the sphygmomanometer cuff, but at a threshold of 10 petechiae (compared with the WHO recommendation of 20) per 2.5 cm2 the sensitivity for the elastic tourniquet rose to 45% (specificity 85%). Other evidence of bleeding was frequently present and the tourniquet test provided additional information to aid diagnosis in only 5% of cases. CONCLUSION: The conventional tourniquet test adds little to the diagnosis of dengue in hospitalized children. The simple, cheap elastic tourniquet may be useful in diagnosing dengue infection in busy rural health stations in dengue endemic areas of the tropics. A positive test should prompt close observation or early hospital referral, but a negative test does not exclude dengue infection.

Adolescent↗
PubMed2004

Relationship of preexisting dengue virus (DV) neutralizing antibody levels to viremia and severity of disease in a prospective cohort study of DV infection in Thailand.

BACKGROUND: Infection with any 1 of the 4 dengue viruses (DVs) can produce several illnesses, ranging from a mild febrile illness to classic dengue fever (DF) to dengue hemorrhagic fever (DHF), a potentially life-threatening disease. Most DHF cases occur after sequential heterotypic DV infections. The role of preexisting humoral immunity in modifying severity of dengue disease is not well understood. METHODS: We conducted a prospective cohort study of children in a region where dengue disease is hyperendemic and examined the role of preexisting neutralizing anti-DV antibodies (Abs) in modifying secondary dengue-3 virus (D3V), dengue-2 virus (D2V), and dengue-1 virus (D1V) infections. RESULTS: In secondary D3V infection, higher levels of preexisting neutralizing Ab directed against D3V (reference virus strain and patient's virus isolate) were associated with lower viremia levels and milder disease. Preexisting neutralizing Ab levels against D2V were not associated with severity of secondary D2V infection. The levels of preexisting neutralizing Ab against the infecting virus isolates were not associated with viremia levels in secondary D2V or D1V infections. CONCLUSIONS: Cross-reactive memory humoral immune responses appear to be beneficial in symptomatic secondary D3V infection, but not in secondary D2V or D1V infection. These results may have important implications for the development of live attenuated tetravalent dengue vaccines.

Adolescent↗
PubMed2006

The comparative accuracy of 8 commercial rapid immunochromatographic assays for the diagnosis of acute dengue virus infection.

BACKGROUND: The serological diagnosis of acute dengue virus infection relies on the detection of dengue-specific immunoglobulin M (IgM) antibodies. Immunochromatographic tests are rapid diagnostic tests (RDTs) that can be performed at the bedside, but they have not been fully validated for diagnosis of dengue infection. METHODS: More than 20 RDTs for diagnosis of acute dengue infection are commercially available. Of these, 8 were selected for evaluation of performance by use of characterized dengue and nondengue serum specimens, and results were compared with those of a previously published dengue IgM/IgG enzyme-linked immunosorbent assay in conjunction with dengue virus serotyping by reverse-transcriptase polymerase chain reaction. RESULTS: Assay sensitivities were low, ranging from 6.4% (95% confidence interval [CI], 4.0%-9.7%) to 65.3% (95% CI, 59.9%-70.5%), and specificities ranged from 69.1% (95% CI, 61.4%-76.0%) to 100% (95% CI, 97.8%-100%). Of the 8 tests, only 2 had sensitivities of >50%, the level considered to be clinically useful, and, of these, 1 had relatively low specificity (69.1%). Samples collected early in the infection were less likely to test positive than those collected later. A thermal stability study demonstrated a loss in performance of some RDTs when they were stored at a high ambient temperature for 3 months. CONCLUSIONS: Users of RDTs for dengue should be aware that many of these tests have a diagnostic accuracy that falls well below the manufacturers' claims. If an acute specimen yields a negative result, a convalescent serum sample should be tested to confirm the result. No RDT adequately differentiated primary and secondary dengue infections, and the tests should not be used for this purpose.

Acute Disease↗
PubMed1997

Dengue in the early febrile phase: viremia and antibody responses.

A multicenter effort was begun in 1994 to characterize the pathophysiology of dengue using a study design that minimized patient selection bias by offering enrollment to all children with undifferentiated fever for <72 h. In the first year, 189 children were enrolled (age range, 8 months to 14 years). Thirty-two percent of these children had dengue infections (60 volunteers). The percentage of children with a secondary dengue infection was 93%, with only 4 (7%) having a primary dengue infection. The virus isolation rate from the plasma of children with dengue was 98%. Viremia correlated highly with temperature. All four dengue virus serotypes were isolated at both study sites. This study demonstrates that all four serotypes of dengue virus can cause dengue hemorrhagic fever, that all dengue patients as defined by serology experience viremia during the febrile phase, and that as fever subsides, so does viremia.

Acute Disease↗
PubMed2006

Recombinant multiepitope protein for early detection of dengue infections.

Dengue fever is a mosquito-borne viral disease prevalent mainly in tropical countries. As the clinical manifestations of dengue are not very unique, laboratory diagnosis is crucial in identifying cases of dengue infection. Detection of dengue infection based on the identification of antidengue antibodies has emerged as a practical and reliable means of diagnosing dengue fever. We recently developed a customized recombinant dengue multiepitope protein (r-DME-G) that can specifically detect the immunoglobulin G (IgG) class of antidengue antibodies in patient sera. Using this strategy, we have now created another dengue multiepitope protein, r-DME-M, with specificity for the IgM class of antidengue antibodies. A synthetic gene encoding the r-DME-M protein was expressed as a maltose-binding protein fusion in Escherichia coli. The recombinant protein was purified in a single affinity chromatographic step to obtain yields of approximately 15 mg purified protein/liter of culture. The purified protein was used to develop an in-house IgM enzyme-linked immunosorbent assay (ELISA) and tested using a panel of 172 patient sera characterized using the commercially available Dengue Duo rapid strip test from PanBio, Australia. The IgM ELISA results showed that the r-DME-M protein not only recognized all IgM(+) samples identified by the PanBio test but also identified samples missed by the latter test. We also successfully adapted the r-DME-M protein to a rapid strip test format. This approach of creating customized antigens coupled to overexpression in E. coli and simple purification offers a promising alternative option to dengue diagnosis with the potential to circumvent the drawbacks of the whole virus antigen-based commercial kits.

Amino Acid Sequence↗
PubMed1998

Typing of dengue viruses in clinical specimens and mosquitoes by single-tube multiplex reverse transcriptase PCR.

In recent years, dengue viruses (serotypes 1 to 4) have spread throughout tropical regions worldwide. In many places, multiple dengue virus serotypes are circulating concurrently, which may increase the risk for the more severe form of the disease, dengue hemorrhagic fever. For the control and prevention of dengue fever, it is important to rapidly detect and type the virus in clinical samples and mosquitoes. Assays based on reverse transcriptase (RT) PCR (RT-PCR) amplification of dengue viral RNA can offer a rapid, sensitive, and specific approach to the typing of dengue viruses. We have reduced a two-step nested RT-PCR protocol to a single-tube reaction with sensitivity equivalent to that of the two-step protocol (1 to 50 PFU) in order to maximize simplicity and minimize the risk of sample cross-contamination. This assay was also optimized for use with a thermostable RT-polymerase. We designed a plasmid-based internal control that produces a uniquely sized product and can be used to control for both reverse transcription or amplification steps without the risk of generating false-positive results. This single-tube RT-PCR procedure was used to type dengue viruses during the 1995 and 1997-1998 outbreaks in Nicaragua. In addition, an extraction procedure that permits the sensitive detection of viral RNA in pools of up to 50 mosquitoes without PCR inhibition or RNA degradation was developed. This assay should serve as a practical tool for use in countries where dengue fever is endemic, in conjunction with classical methods for surveillance and epidemiology of dengue viruses.

Aedes↗
PubMed2000

Recombinant chimeric yellow fever-dengue type 2 virus is immunogenic and protective in nonhuman primates.

A chimeric yellow fever (YF)-dengue type 2 (dengue-2) virus (ChimeriVax-D2) was constructed using a recombinant cDNA infectious clone of a YF vaccine strain (YF 17D) as a backbone into which we inserted the premembrane (prM) and envelope (E) genes of dengue-2 virus (strain PUO-218 from a case of dengue fever in Bangkok, Thailand). The chimeric virus was recovered from the supernatant of Vero cells transfected with RNA transcripts and amplified once in these cells to yield a titer of 6.3 log(10) PFU/ml. The ChimeriVax-D2 was not neurovirulent for 4-week-old outbred mice inoculated intracerebrally. This virus was evaluated in rhesus monkeys for its safety (induction of viremia) and protective efficacy (induction of anti-dengue-2 neutralizing antibodies and protection against challenge). In one experiment, groups of non-YF-immune monkeys received graded doses of ChimeriVax-D2; a control group received only the vaccine diluents. All monkeys (except the control group) developed a brief viremia and showed no signs of illness. Sixty-two days postimmunization, animals were challenged with 5.0 log(10) focus forming units (FFU) of a wild-type dengue-2 virus. No viremia (<1.7 log(10) FFU/ml) was detected in any vaccinated group, whereas all animals in the placebo control group developed viremia. All vaccinated monkeys developed neutralizing antibodies in a dose-dependent response. In another experiment, viremia and production of neutralizing antibodies were determined in YF-immune monkeys that received either ChimeriVax-D2 or a wild-type dengue-2 virus. Low viremia was detected in ChimeriVax-D2-inoculated monkeys, whereas all dengue-2-immunized animals became viremic. All of these animals were protected against challenge with a wild-type dengue-2 virus, whereas all YF-immune monkeys and nonimmune controls became viremic upon challenge. Genetic stability of ChimeriVax-D2 was assessed by continuous in vitro passage in VeroPM cells. The titer of ChimeriVax-D2, the attenuated phenotype for 4-week-old mice, and the sequence of the inserted prME genes were unchanged after 18 passages in Vero cells. The high replication efficiency, attenuation phenotype in mice and monkeys, immunogenicity and protective efficacy, and genomic stability of ChimeriVax-D2 justify it as a novel vaccine candidate to be evaluated in humans.

Amino Acid Substitution↗
PubMed2004

Virus Overlay Protein Binding Assay (VOPBA) reveals serotype specific heterogeneity of dengue virus binding proteins on HepG2 human liver cells.

OBJECTIVE: This study sought to investigate the presence of dengue virus binding proteins expressed on the surface of HepG2 cells and to determine if there were serotype specific differences in binding. METHODS: HepG2 cell membrane proteins were extracted and separated by SDS-PAGE, transferred to nitrocellulose membranes and incubated with dengue virus serotypes 2, 3 and 4 under varying hybridization conditions. The positions of dengue virus binding proteins were established with a pan-specific anti-dengue virus monoclonal antibody. RESULTS: Dengue virus binding proteins were seen at approximately 78-80, 90, 98, and 102 kD for dengue serotype 2, 90, 130 and 182 kD for dengue serotype 3, and 90 and 130 kD for dengue serotype 4. Binding of the serotypes 3 and 4 was significantly altered by the hybridization conditions, while serotype 2 was affected to a lesser extent. CONCLUSIONS: The virus overlay assay used here provides further evidence that there is a serotype specific component regulating the entry of the dengue virus into cells. Given that several virus binding proteins are seen for each serotype, multiple proteins may be required to facilitate the entry of the virus into some cell types.

Biological Assay↗
PubMed2006

Enzyme-linked immunoassay for dengue virus IgM and IgG antibodies in serum and filter paper blood.

BACKGROUND: The reproducibilty of dengue IgM and IgG ELISA was studied in serum and filter paper blood spots from Vietnamese febrile patients. METHODS: 781 pairs of acute (t0) and convalescent sera, obtained after three weeks (t3) and 161 corresponding pairs of filter paper blood spots were tested with ELISA for dengue IgG and IgM. 74 serum pairs were tested again in another laboratory with similar methods, after a mean of 252 days. RESULTS: Cases were classified as no dengue (10 %), past dengue (55%) acute primary (7%) or secondary (28%) dengue. Significant differences between the two laboratories' results were found leading to different diagnostic classification (kappa 0.46, p < 0.001). Filter paper results correlated poorly to serum values, being more variable and lower with a mean (95% CI) difference of 0.82 (0.36 to 1.28) for IgMt3, 0.94 (0.51 to 1.37) for IgGt0 and 0.26 (-0.20 to 0.71) for IgGt3. This also led to differences in diagnostic classification (kappa value 0.44, p < 0.001) The duration of storage of frozen serum and dried filter papers, sealed in nylon bags in an air-conditioned room, had no significant effect on the ELISA results. CONCLUSION: Dengue virus IgG antibodies in serum and filter papers was not affected by duration of storage, but was subject to inter-laboratory variability. Dengue virus IgM antibodies measured in serum reconstituted from blood spots on filter papers were lower than in serum, in particular in the acute phase of disease. Therefore this method limits its value for diagnostic confirmation of individual patients with dengue virus infections. However the detection of dengue virus IgG antibodies eluted from filter paper can be used for sero-prevalence cross sectional studies.

Antibodies, Viral↗
PubMed2006

The changing epidemiology of dengue in Delhi, India.

BACKGROUND: A major DHF outbreak occurred in Delhi in 1996. Following this another outbreak was reported in the year 2003. In the years 2004 and 2005, though no outbreak was reported, a definitely higher number of samples were received in the virology laboratory of A.I.I.M.S. from suspected cases of dengue infection. This study was designed to compare the serological and virological profiles of confirmed dengue cases in the years 2003, 2004 and 2005. RESULTS: Out of 1820 serum samples received from suspected cases in all three years, 811 (44.56%) were confirmed as dengue infection serologically. Out of these confirmed dengue cases maximum cases, in all three years, were seen in the age group 21-30 years. There was an increase in the number of samples received in the post monsoon period (September to November) with a peak in the second and third week of October. More samples were received from DHF cases in the year 2005 than 2004 and 2003. All four dengue serotypes were seen co-circulating in the year 2003, followed by complete predominance of dengue serotype 3 in 2005. CONCLUSION: Epidemiology of dengue is changing rapidly in Delhi. Dengue infections are seen every year thus making it an endemic disease. After co-circulation of all serotypes in 2003, now dengue serotype 3 is emerging as the predominant serotype.

Adolescent↗