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PubMed2004

Serological markers during dengue 3 primary and secondary infections.

BACKGROUND: The detection of the IgM antibody for the dengue virus in serum by ELISA has become one of the most important and useful methods for diagnosis of dengue using a single acute-phase serum sample. Currently, this system is an invaluable tool for the surveillance of dengue fever (DF) and dengue hemorrhagic fever (DHF). The usefulness of other serological markers such as IgA and IgE have been less studied. OBJECTIVE: To study the IgM, IgA and IgE specific antibody response in dengue 3 infected patients with different clinical picture and type of infection. STUDY DESIGN: One hundred and twenty-seven serum samples collected on days 5-7 at the onset of fever from clinically and serologically confirmed dengue cases were studied. Forty-two were classified as primary dengue fever cases, 48 as secondary dengue fever cases and 37 as secondary dengue hemorrhagic fever cases. All samples were tested by capture ELISA in order to detect dengue IgM, IgA and IgE antibodies. RESULTS AND CONCLUSIONS: In this study, significant differences were observed in the IgM, IgA and IgE response between the study groups. High IgA and IgE OD ratios in secondary dengue cases were found. The usefulness of serotype specific IgM antibody detection is also analyzed and discussed. A priority for future dengue research in terms of protection, recovery of infection and immunopathogenesis is to elucidate the role of these immunoglobulins. The cross reactivity response to IgM between dengue virus serotypes in primary and secondary cases should also be more studied.

Antibodies, Viral↗
PubMed2005

Secondary dengue virus type 4 infections in Vietnam.

This study was designated to describe clinical and biological features of patients with a suspected diagnosis of dengue fever/dengue hemorrhagic fever during an outbreak in Central Vietnam. One hundred and twenty-five consecutive patients hospitalized at Khanh Hoa and Binh Thuan Provincial hospitals between November 2001 and January 2002 with a diagnosis of suspected dengue infection were included in the present study. Viruses were isolated in C6/36 and VERO E6 cell cultures or detected by RT-PCR. A hemagglutination-inhibition test (HI) was done on each paired sera using dengue antigens type 1-4, Japanese encephalitis (JE) virus antigen, Chickungunya virus antigen and Sindbis virus antigen. Anti-dengue and anti-JE virus IgM were measured by a capture enzyme-linked immunosorbent assay (MAC-ELISA). Anti-dengue and anti-JE virus IgG were measured by an ELISA test. Dengue viruses were isolated in cell culture and/or detected by RT-PCR in 20.8% of blood samples. DEN-4 and DEN-2 serotypes were found in 18.4% and 2.4% of the patients, respectively. A total of 86.4% of individuals had a diagnosis of acute dengue fever by using the HI test and/or dengue virus-specific IgM capture-ELISA and/or virus isolation and/or RT-PCR. The prevalence of primary and secondary acute dengue infection was 4% and 78.4%, respectively. Anti-dengue IgG ELISA test was positive in 88.8% of the patients. In 5 cases (4%), Japanese encephalitis virus infection was positive by serology but the cell culture was negative. No Chickungunya virus or Sindbis virus infection was detected by the HI test. In patients with acute dengue virus infection, the most common presenting symptom was headache, followed by conjunctivitis, petechial rash, muscle and joint pain, nausea and abdominal pain. Four percent of hospitalized patients were classified as dengue hemorrhagic fever. The clinical presentation and blood cell counts were similar between patients hospitalized with acute dengue fever and patients with other febrile illnesses.

Adolescent↗
PubMed1995

Diagnosing dengue virus infection in archived autopsy tissues by means of the in situ PCR method: a case report.

BACKGROUND: The pathogenesis of the severe form of dengue virus infection, dengue hemorrhagic fever, is still obscure. A major research objective has been to determine which body organs are being damaged by dengue virus in this form of dengue. Research has been difficult because dengue hemorrhagic fever is sporadic and tends to occur in parts of the world where modern facilities are scarce and fresh or frozen patient materials are not available. However, major hospitals in these areas have accumulated libraries of paraffin-embedded surgical and autopsy tissues over the years. These tissues may have been subjected to less than optimal fixation and storage. Attempts to localize dengue virus using antigen detection in the stored tissue have encountered many difficulties. OBJECTIVE: Since viral nucleic acid may be preserved under circumstances which destroy protein antigens, our objective was to detect dengue viral RNA in situ in histologic sections of tissues from patients dying of dengue hemorrhagic fever in Thailand. STUDY DESIGN: Tissues from an 11-year-old boy who died at Ramathibodi Hospital, Bangkok, Thailand in November, 1987 with the clinical diagnosis of dengue hemorrhagic fever were treated by transcribing the dengue viral RNA to DNA followed by amplification using the polymerase chain reaction with subsequent in situ hybridization in order to visualize the cells infected with dengue virus. RESULTS: Viral RNA was detected in hepatocytes in the mid-zonal region of the liver, as well as scattered macrophages in skin and lymph nodes. CONCLUSION: Dengue virus infection can be detected in paraffin-embedded autopsy tissues which have been stored for five years. The same procedure can be used for diagnosing dengue viral infection and for studying the pathogenesis of dengue hemorrhagic fever.

Journal Article↗
PubMed1997

Recognition of dengue virus NS1-NS2a proteins by human CD4+ cytotoxic T lymphocyte clones.

We examined nine dengue virus-specific human CD4+ CD8- cytotoxic T lymphocyte (CTL) clones for protein recognition, using recombinant vaccinia viruses which contain genes coding for dengue virus proteins. These clones were established from peripheral blood mononuclear cells of a donor previously immunized with a live-attenuated experimental dengue-1 vaccine. Of nine CD4+ T cell clones, seven were dengue-1-specific and two were dengue-1-dengue-3 cross-reactive. Four dengue-1-specific clones and one dengue-1-dengue-3 cross-reactive clone recognized epitopes within the NS1 or NS2a proteins. Analysis of human leukocyte antigen (HLA) restriction revealed that three dengue-1-specific clones are HLA-DR1-restricted and one dengue-1-dengue-3 cross-reactive clone is HLA-DPw3-restricted. These results indicate that NS1 and NS2a proteins as well as C, E, and NS3 proteins reported earlier contain one or more epitopes recognized by dengue virus-specific human CD4+ T lymphocytes.

Antigens, Viral↗
PubMed2000

Invited commentary: Dengue lessons from Cuba.

An 18-year interval between a dengue virus type 1 outbreak in 1977-1979 and a dengue virus type 2 outbreak in 1997 in Santiago de Cuba, Cuba, provided a unique opportunity to evaluate risk factors for dengue disease. All patients with symptomatic dengue, including 205 cases of dengue hemorrhagic fever and 12 deaths, were adults born before the dengue virus type 1 epidemic, and nearly all (98%) experienced secondary dengue virus infections. In contrast, almost all of those who seroconverted without illness (97%) experienced primary dengue virus infection. This provides epidemiologic support for the immune enhancement theory of dengue pathogenesis. The Cuban experience suggests that immune enhancement can be seen even 20 years after the primary dengue virus infection. It also supports the contention that primary infections with dengue virus type 2 (and dengue virus type 4) are largely subclinical. These observations have implications for dengue vaccine development based on live-attenuated viruses.

Adult↗
PubMed2002

Dengue virus infections.

Dengue is the most important arthropod-borne viral disease of public health significance. Its geographic distribution includes more than 100 countries worldwide, where more than 2.5 billion people are at risk for dengue infections. Most people will have asymptomatic infections, but the disease manifestations range from an influenza-like disease known as dengue fever to a severe, sometimes fatal disease characterized by hemorrhage and shock, known as dengue hemorrhagic fever/dengue shock syndrome. Dengue fever and dengue hemorrhagic fever/dengue shock syndrome are caused by the dengue viruses (dengue-1, dengue-2, dengue-3, and dengue-4) transmitted from viremic to susceptible humans mainly by the bites of Aedes aegypti. There is no specific management of dengue infections, no vaccine is commercially available, and vector control is the only alternative for stopping the spread of the disease. Knowledge of several aspects of dengue infections, especially of diagnosis and vaccine development, is continuously evolving, but several issues are still unresolved.

Child↗
PubMed1986

Hemadsorption immunosorbent technique for the detection of dengue immunoglobulin M antibody.

We developed a highly specific, sensitive, and economical hemadsorption immunosorbent technique for the detection of dengue-specific immunoglobulin M (IgM) antibody. The technique is based on the reaction of human sera with anti-human IgM immobilized onto a solid phase followed by the detection of dengue-specific IgM by the addition of a known quantity of dengue virus hemagglutinin and goose erythrocytes. Dengue-specific IgM-positive sera showed hemadsorption. IgM antibody specific for dengue virus was detected in 22 of 39 (56%) convalescent-phase sera from primary dengue infections and 8 of 10 (80%) convalescent-phase sera from secondary dengue infections. Additionally, 32 of 76 single sera from patients were positive for dengue IgM; these sera were previously uninterpretable by the hemagglutination inhibition test, as only a single serum specimen was available. No false-positive results were obtained with sera that were negative by the hemagglutination inhibition test for dengue virus. Crude dengue virus hemagglutinin preparations could be used without purification. Dengue-specific IgG did not interfere with the results, nor was there any cross-reactivity between dengue hemagglutinins and IgM specific for other viruses. Some cross-reactivity of the dengue-specific IgM was observed with Japanese encephalitis virus hemagglutinins, but this did not present any problems in the interpretation of results. This test is specific, inexpensive, highly reproducible, and simple to perform.

Antibodies, Viral↗
PubMed1998

Monitoring of dengue viruses in field-caught Aedes aegypti and Aedes albopictus mosquitoes by a type-specific polymerase chain reaction and cycle sequencing.

Virologic surveillance for dengue through the detection of the prevalent serotype(s) circulating in the human population during inter- and intra-epidemic periods constitutes a reliable sentinel system for dengue outbreaks. We have applied a rapid and sensitive, semi-nested, reverse transcription-polymerase chain reaction (RT-PCR) assay using nonstructural protein 3 gene primers for the type-specific-detection of dengue viruses in artificially infected and in field-caught adult Aedes mosquitoes. In laboratory experiments, the assay was sensitive enough to detect one virus-infected mosquito head in pools of up to 59 uninfected heads. In a prospective field study conducted from April 1995 to July 1996, female adult Ae. aegypti and Ae. albopictus mosquitoes were caught from selected dengue-sensitive areas in Singapore and assayed by RT-PCR. Approximately 20% of 309 mosquito pools were positive for dengue viruses. Of the 23 RT-PCR-positive Ae. aegypti pools (containing 1-17 mosquitoes each), 18 pools (78.3%) were positive for dengue 1 virus. There were 40 RT-PCR-positive Ae. albopictus pools (containing 1-33 mosquitoes each) of which 31 (77.5%) were positive for dengue 1 virus. The predominant virus type responsible for the current dengue epidemic since 1995 was also dengue 1. The geographic locations of the virus-infected mosquitoes correlated with the residences or workplaces of patients within dengue outbreak areas. A total of 43.5% of the positive Ae. aegypti pools and 25.0% of the positive Ae. albopictus pools contained only a single mosquito. Both Aedes species showed similar overall minimum infection rates of 57.6 and 50 per 1,000 mosquitoes. Infected Ae. aegypti were detected as early as six weeks before the start of the dengue outbreaks in 1995 and 1996. However, infected Ae. albopictus appeared later, when the number of cases was increasing. Virologic surveillance by RT-PCR for detecting dengue virus-infected Aedes mosquitoes in the field may serve as an early warning monitoring system for dengue outbreaks.

Aedes↗
PubMed2005

Emergence of dengue virus type-3 in northern India.

During the last few decades dengue has reemerged in several parts of Southeast Asia, including India. A major outbreak of dengue infection occurred in northern India during October to December 2003. To determine the etiology, we carried out serological, virological and molecular investigations of this outbreak. A total of 76 dengue suspected patient blood samples were collected from Gwalior, Madhya Pradesh and Delhi, India. Serological investigations carried out using an in-house Dipstick ELISA protocol revealed the presence of anti-dengue antibodies in 53 patients. Twelve of them (22%) had a positive IgM response, indicative of primary infection, and 22 of them (42%) revealed only IgG antibodies, indicative of secondary infection. RT-PCR analysis employing dengue group specific amplimer revealed the presence of dengue specific RNA in four acute phase samples. These four RT-PCR positive samples were further processed for virus isolation in C6/36 cells and suckling mice, yielding four dengue virus isolates. The Nested PCR analysis employing serotype specific amplimer revealed the presence of dengue-3 specific 389 bp amplicon. This study confirmed the reemergence of dengue virus type-3 in a dominant form in India after a gap of nine years. Earlier, dengue virus type-2 was implicated as the etiology of a major dengue epidemic in Delhi in 1996 and Gwalior in 2001. The implication of dengue type-3 as etiology of a DHF epidemic in neighboring Sri Lanka and Bangladesh recently confirms the reemergence of dengue type-3 as the dominant form on the Indian subcontinent.

Adolescent↗
PubMed1990

Human IgG Fc receptor II mediates antibody-dependent enhancement of dengue virus infection.

It is known that anti-dengue virus antibodies at subneutralizing concentrations augment dengue virus infection of IgG FcR (Fc gamma R)-positive cells, and this phenomenon is called antibody-dependent enhancement. This is caused by the uptake of dengue virus-antibody complexes by Fc gamma R. We previously reported that Fc gamma RI can mediate antibody-dependent enhancement. In this study we use an erythroleukemia cell line, K562, which has Fc gamma RII, but does not have Fc gamma RI or Fc gamma RIII, to determine if Fc gamma RII can mediate infection by dengue virus-antibody complexes. Polyclonal mouse anti-dengue virus antibody significantly augments dengue virus infection of K562 cells, whereas normal mouse serum does not. A mAb IV.3, which is specific for Fc gamma RII and is known to inhibit the binding of Ag-antibody complex to Fc gamma RII, inhibits dengue antibody-mediated augmentation of dengue virus infection. It has been reported that Fc gamma RII binds to mouse IgG1, but not to mouse IgG2a. A mouse IgG1 anti-dengue virus mAb (3H5) augments dengue virus infection of K562 cells, but a mouse IgG2a anti-dengue virus mAb (4G2) does not. 4G2 augments dengue virus infection of a human monocytic cell line, U937, which has Fc gamma RI. Based on these results we conclude that Fc gamma RII mediate antibody-dependent enhancement of dengue virus infection in addition to Fc gamma RI.

Antibodies, Monoclonal↗
PubMed1994

Dengue surveillance--United States, 1986-1992.

PROBLEM/CONDITION: Dengue is an acute, mosquito-transmitted viral disease characterized by fever, headache, arthralgia, myalgia, rash, nausea, and vomiting. The worldwide incidence of dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS) increased from the mid-1970s through 1992. Although dengue is not endemic to the 50 United States, it presents a risk to U.S. residents who visit dengue-endemic areas. REPORTING PERIOD COVERED: 1986-1992. DESCRIPTION OF SYSTEM: Dengue surveillance in the 50 United States and the U.S. Virgin Islands relies on provider-initiated reports to state health departments. State health departments then submit clinical information and serum samples to CDC for diagnostic confirmation of disease among U.S. residents who become ill during or after travel to dengue-endemic areas and among residents of the U.S. Virgin Islands. In Puerto Rico, an active, laboratory-based surveillance program receives serum specimens from ambulatory and hospitalized patients throughout the island, clinical reports on hospitalized cases, and copies of death certificates that list dengue as a cause of death. Laboratory diagnosis relies on virus isolation or serologic diagnosis of disease (i.e., IgM or IgG antibodies against dengue viruses). RESULTS: In 1986, the first indigenous transmission of dengue in the United States in 6 years occurred in Texas; from the time of that incident through 1992, however, no further endemic transmission was reported. During 1986-1992, CDC processed serum samples from 788 residents of 47 states and the District of Columbia. Among these 788 residents, 157 (20%) cases of dengue were diagnosed serologically or virologically. Of the 157 patients, 71 (45%) had visited Latin America or the Caribbean; 63 (40%), Asia and the Pacific; seven (4%), Africa; and nine (6%), several continents. All four dengue virus serotypes (DEN-1, DEN-2, DEN-3, and DEN-4) were isolated from travelers to Asia and the Pacific; however, travelers to the Americas acquired infections with only DEN-1, DEN-2, or DEN-4. Even though the number of laboratory-diagnosed dengue infections among travelers was small, severe and fatal disease was documented. In the U.S. Virgin Islands and Puerto Rico, three serotypes (DEN-1, DEN-2, and DEN-4) circulated during 1986-1992. In Puerto Rico, disease transmission was characterized by a cyclical pattern, with peaks in incidence occurring during months with higher temperatures and humidity (usually from September through November). The highest incidence of laboratory-diagnosed disease (1.2 cases per 1,000 population) occurred among persons < 30 years of age; rates were similar for males and females.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

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

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.

Antibodies, Viral↗
PubMed2005

A variant in the CD209 promoter is associated with severity of dengue disease.

Dengue fever and dengue hemorrhagic fever are mosquito-borne viral diseases. Dendritic cell-specific ICAM-3 grabbing nonintegrin (DC-SIGN1, encoded by CD209), an attachment receptor of dengue virus, is essential for productive infection of dendritic cells. Here, we report strong association between a promoter variant of CD209, DCSIGN1-336, and risk of dengue fever compared with dengue hemorrhagic fever or population controls. The G allele of the variant DCSIGN1-336 was associated with strong protection against dengue fever in three independent cohorts from Thailand, with a carrier frequency of 4.7% in individuals with dengue fever compared with 22.4% in individuals with dengue hemorrhagic fever (odds ratio for risk of dengue hemorrhagic fever versus dengue fever: 5.84, P = 1.4 x 10(-7)) and 19.5% in controls (odds ratio for protection: 4.90, P = 2 x 10(-6)). This variant affects an Sp1-like binding site and transcriptional activity in vitro. These results indicate that CD209 has a crucial role in dengue pathogenesis, which discriminates between severe dengue fever and dengue hemorrhagic fever. This may have consequences for therapeutic and preventive strategies.

Cell Adhesion Molecules↗
PubMed2006

Multi-level analyses of spatial and temporal determinants for dengue infection.

BACKGROUND: Dengue is a mosquito-borne viral infection that is now endemic in most tropical countries. In Thailand, dengue fever/dengue hemorrhagic fever is a leading cause of hospitalization and death among children. A longitudinal study among 1750 people in two rural and one urban sites in northern Thailand from 2001 to 2003 studied spatial and temporal determinants for recent dengue infection at three levels (time, individual and household). METHOD: Determinants for dengue infection were measured by questionnaire, land-cover maps and GIS. IgM antibodies against dengue were detected by ELISA. Three-level multi-level analysis was used to study the risk determinants of recent dengue infection. RESULTS: Rates of recent dengue infection varied substantially in time from 4 to 30%, peaking in 2002. Determinants for recent dengue infection differed per site. Spatial clustering was observed, demonstrating variation in local infection patterns. Most of the variation in recent dengue infection was explained at the time-period level. Location of a person and the environment around the house (including irrigated fields and orchards) were important determinants for recent dengue infection. CONCLUSION: We showed the focal nature of asymptomatic dengue infections. The great variation of determinants for recent dengue infection in space and time should be taken into account when designing local dengue control programs.

Adolescent↗
PubMed2005

Serum and urine sodium levels in dengue patients.

We evaluated serum and urine sodium levels in children with dengue infections. Children with acute febrile illness admitted to Bhumibol Adulyadej Hospital in Bangkok from January 1999 to January 2000 were enrolled. Serum and urine sodium levels were measured before initiating intravenous fluid therapy. Two milliliters of blood were obtained on admission and before discharge to test for anti-dengue virus antibody using the enzyme-linked immunosorbent assay technique. Hyponatremia was defined as a serum sodium level <130 mEq/l and depletion of circulatory volume was defined as a urine sodium level < 20 mEq/l. Out of 93 enrolled patients, 49 were categorized as dengue patients and 44 were as non-dengue patients. Six dengue patients developed shock whereas 43 patients did not. The mean serum sodium level was significantly lower in dengue patients compared to non-dengue patients (p-value < 0.0001). Hyponatremia was 9.7 times more common in dengue patients. Among dengue patients, the mean serum sodium level was significantly lower in shock patients compared to non-shock patients (p-value = 0.003). However, the prevalence of hyponatremia was not different between the two groups. The mean urine sodium level was significantly lower in dengue patients compared to non-dengue patients (p-value < 0.0001). A urine sodium level < or = 20 mEq/l was 8.1 times more common in dengue patients. Among dengue patients, the mean urine sodium level was not significantly different between shock and non-shock patients. In shock patients, a urine sodium level < or = 20 mEq/l was 7.6 times more common.

Acute Disease↗
PubMedDate not supplied

Gallbladder edema in Dengue hemorrhagic fever and its association with haematocrit levels and type of infections.

AIM: To determine gallbladder edema with type of Dengue infection and hematocrit level. METHODS: A retrospective study was performed on 225 cases of DHF admitted from January to December 1997 to determine the association between the type of Dengue infection, hemoconcentration and the presence or absence of gallbladder edema. Primary or secondary types of Dengue infection consider to determine the severity and degree of plasma leakage in dengue hemorrhagic fever. The Chi square and Spearman 's tests were performed to establish association between variables. RESULTS: out of 225 cases of DHE 129 cases were found with the following dengue serology test results: 92 IgM positive and 37 negative. Abdominal ultrasound was performed in 57 cases, revealing gallbladder edema in 17 cases and none in 40 cases. The 57 cases were classified as primary dengue cases (positive IgMA), secondary dengue(positive IgM and IgG), or seronegative (negative IgM). Primary dengue was found in 5 cases with gallbladder edema and 15 cases without (25%). In the secondary dengue group,10 cases were found with gallbladder edema and 8 cases without (55.5%), while in the non-Dengue group, there were 2 cases with gallbladder edema and 17 cases without (10.5%). There was association between the development of gallbladder edema and the type of dengue infection(p=0.010). Gallbladder edema was more common in secondary Dengue (55%). There was a tendency for gallbladder edema in patients with higher increases in hematocrit. CONCLUSION: It conclude that gallbladder edema is more common in cases of secondary dengue and that there is a tendency for gallbladder edema with higher increase of hematocrit.

Edema↗
PubMed1993

[The 1991 dengue epidemic in Kaohsiung City].

In Kaohsiung City, dengue fever subsided for two years after the 1987-1988 epidemic. The main reason that it recurred was due to late diagnoses of the dengue fever in patients because of mild or atypical clinical presentations. The first patient contracted dengue fever from Thailand in mid-May, 1991. The disease then spread among his co-workers. Dengue fever was not suspected until the 9th patient contracted it in early July 1991. Through chain transmission, the epidemic spread in the community and even to other parts of Taiwan. There were 113 confirmed dengue cases in Kaohsiung City, and a total of 175 cases on the whole island during the 1991 epidemic. The clinical manifestations were mainly fever, body pain, dizziness, general weakness, and a skin rash. No instances of severe bleeding, shock or dengue hemorrhagic fever were found. Seven dengue 1 and three dengue 3 viruses were isolated from the sera of patients. We found that the clinical severity of the 1991 dengue epidemic was milder, and the viral isolation rate was lower, compared with the 1987-1988 epidemic, although these two outbreaks of dengue fever were both mostly due to dengue type 1. Genetic variation in the dengue virus may be the explanation. Clinically, about 35% of the patients were missed or not reported, although they were finally demonstrated to be dengue fever patients during a patient survey in the epidemic area. For early detection, viral surveys should be performed in new epidemic regions in addition to fixed-spot surveillance.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

Evaluation of RT-PCR as a tool for diagnosis of secondary dengue virus infection.

Dengue fever and dengue hemorrhagic fever are serious illnesses in many tropical and subtropical countries. Laboratory tests are essential for the confirmation of dengue virus infection. In the present study, we examined the reliability of reverse transcriptase polymerase chain reaction (RT-PCR) in the laboratory diagnosis of dengue, especially in secondary dengue virus infections. We defined the day when fever subsided as fever day 0. In primary dengue virus infection, the dengue viral genome was detected in all of the 7 samples which were collected on fever day -1 or earlier, in 3 of 4 samples on fever day 0, and in 1 of 2 samples on fever day 1. None of the samples collected on fever day 2 or later were positive by RT-PCR. In secondary dengue virus infection, the dengue viral genome was detected in all of the 28 samples which were collected on fever day -2 or earlier, in 25 of 26 on fever day -1, in 29 of 34 on fever day 0, and in 5 of 10 on fever days 1-2. None of the samples collected on fever day 3 or later were positive. Virus isolation and direct titration were attempted using the plasma samples. When the data of secondary infection cases were analyzed based on fever day, dengue viruses were isolated from all of the 5 samples which were collected on fever day -2 or earlier, in 5 of 13 samples on fever day -1, and in 4 of 22 on fever day 0, but were not isolated from any of the 4 samples collected on fever days 1-2. Viruses were directly detected in 7 of 11 samples on fever day -2 or earlier, in 4 of 13 on fever day -1, and in 1 of 16 on fever day 0. These results indicate that RT-PCR is more sensitive than virus isolation and direct virus titration for determining secondary dengue virus infection. The results also suggest that RT-PCR is a useful diagnostic test for confirmation of dengue virus infection in secondary infection as well as in primary infection, especially when plasma samples are collected before the fever subsides.

Antibodies, Viral↗