Effect of age on outcome of secondary dengue 2 infections.

OBJECTIVE: Dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS) is a growing global health problem. It is not known how age affects the outcome of secondary dengue infections. In an island setting, a large DHF/DSS outbreak in Cuba occurred in 1981. Involved were individuals, 3-40 year old, whose only lifetime dengue exposure was to DEN-1 in 1977 and DEN-2 in 1981. In this report we calculate age-specific DHF/DSS hospitalization and death rates based on secondary DEN 2 infections. METHODS: Published and unpublished hospital and seroepidemiologic data from the 1981 DHF/DSS outbreak were used for the analysis. RESULTS: Children, aged 3 and 4 years, with secondary DEN-2 infections were found to have a high death rate (25.4/10 000 secondary DEN-2 infections). The death rate fell with increasing age, being 15.9-fold lower in the 10-14-year age group. The death rate for children aged 3-14 years was 14.5-fold higher than in young adults aged 15-39 years. The death rate rose somewhat in adults aged 50 years and older. DHF/DSS hospitalization rates showed the same trend as death rates. CONCLUSIONS: Age is an important variable in the outcome of secondary DEN-2 infections. DHF/DSS case fatality and hospitalization rates are highest in young infants and the elderly. The risk that a child will die during a secondary DEN-2 infection is nearly 15-fold higher than the risk in adults.     

Epidemiology of dengue and dengue hemorrhagic fever in a cohort of adults living in Bandung, West Java, Indonesia

A prospective study of dengue fever (DF) and dengue hemorrhagic fever (DHF) was conducted in a cohort of adult volunteers from two textile factories located in West Java, Indonesia. Volunteers in the cohort were bled every three months and were actively followed for the occurrence of dengue (DEN) disease. The first two years of the study showed an incidence of symptomatic DEN disease of 18 cases per 1,000 person-years and an estimated asymptomatic/ mild infection rate of 56 cases per 1,000 person-years in areas of high disease transmission. In areas where no symptomatic cases were detected, the incidence of asymptomatic or mild infection was 8 cases per 1,000 person-years. Dengue-2 virus was the predominant serotype identified, but all four serotypes were detected among the cohort. Four cases of DHF and one case of dengue shock syndrome (DSS) were identified. Three of the four DHF cases were due to DEN-3 virus. The one DSS case occurred in the setting of a prior DEN-2 virus infection, followed by a secondary infection with DEN-1 virus. To our knowledge, this is the first report of a longitudinal cohort study of naturally acquired DF and DHF in adults.     

Use of nucleotide sequencing of the genomic cDNA fragments of the capsid/premembrane junction region for molecular epidemiology of dengue type 2 viruses

The recent emergence of dengue hemorrhagic fever/dengue shock syndrome (DHF/ DSS) in India has been a source of concern. In the present study a quantitative comparison of 406 nucleotide long sequence from the capsid-premembrane junction region (C-PrM) of 9 dengue virus type 2 (DEN-2) isolates from Delhi with 10 DEN-2 isolates from diverse geographic areas provided sufficient information for estimating genetic relationships. The data indicated that the 1996 epidemic of DHF in Delhi was caused by genotype IV strains of DEN-2. This genotype, perhaps, displaced genotype V strains of DEN-2, which was circulating genotype in 1967. The period during which this displacement had occurred is not clear from the present study. Nonetheless, similar experience in four countries in Latin America and in Sri Lanka suggest that the introduction of new genotypes of DEN-2 displacing the circulating genotype may be associated with the appearance of DHF/DSS. More work is required to elucidate this hypothesis. Transitions at nucleotide positions 406 and 431 resulted in amino acid substitutions near (aa position 104, methionine --> valine) and at the hinge region (aa position 112, valine --> alanine) of C-PrM, respectively in all/most genotypes of group III and IV DEN-2 viruses analysed. Most of these virus strains have been isolated from DHF/DSS outbreaks. Significance of this observation is discussed. The data presented in this study suggest the utility of C-PrM sequence analysis for molecular epidemiology of dengue viruses.     

福建省1株登革Ⅱ型病毒的鉴定

目的对2005年福建省分离的1株登革病毒(DV)进行鉴定,并从分子水平追踪其可能的传染源。方法采用酶联免疫吸附试验(ELISA)检测疑似登革热患者血清中DV(IgM、IgG抗体;同时应用C6/36细胞、单克隆抗体间接免疫荧光(McAb-IFA)、逆转录(套式PCR法分别进行病毒的分离和鉴定,并对分离株的部分基因进行核苷酸序列分析。结果患者血清登革病毒特异性IgM抗体阳性、IgG抗体可疑,表明该患者在近期感染过登革病毒。患者血清接种C6/36细胞,观察到登革病毒特有的CPE。受感染的C6/36细胞能与登革病毒Ⅱ型单克隆抗体反应,表明分离的病毒株为登革Ⅱ型病毒。分离株的核酸提取物经RT(PCR扩增,登革病毒通用引物可扩增出511bp的特异性条带,型特异性引物扩增出119bp的特异性条带,进一步证实分离的病毒株为登革Ⅱ型病毒。分离株RT(PCR扩增产物的核苷酸序列与30株不同地域来源的登革Ⅱ型病毒相应序列构建的系统发生树表明,此毒株与东南亚地区的毒株比较接近。此次分离株的序列与1999年登革Ⅱ型病毒福建株的对应序列在亲缘关系上有一定程度距离。结合流行病学调查资料,进一步确定此病例为输入性感染病例。结论福建省首次从输入性登革热患者血清中分离出登革Ⅱ型病毒,该病毒来源于东南亚地区。     

Double infection of heteroserotypes of dengue viruses in field populations of Aedes aegypti and Aedes albopictus (Diptera: Culicidae) and serological features of dengue viruses found in patients in southern Thailand

In order to understand more about the epidemiology of DHF, a study of the type of dengue viruses and vectors under natural conditions was carried out. Mosquito vectors in the field and the serum of DHF patients in southern Thailand were examined. The two mosquito species are abundant and DHF incidence remains high in this region. Dengue viruses were examined in field-caught mosquitoes by RT-PCR technique. The mosquitoes were caught in 4 provinces: Krabi, Phuket, Phang-Nga and Surat Thani during the late dry season until the early rainy season in 2005. Three dengue serotypes (DEN-2, DEN-3, DEN-4) were detected in Ae. aegypti males and females, and 2 (DEN-2, DEN-3) were detected in Ae. albopictus females. Double infection with 2 serotypes of dengue viruses (DEN-2 and DEN-3) were detected in Ae. aegypti males and females and Ae. albopictus females. DEN-2 and DEN-1 were the most prevalent serotypes found in the serum of the patients in this area, followed by DEN-4 and DEN-3. The prevalence of the predominant dengue serotype varied from province to province. Detection of viruses in adult male mosquitoes reveals the role of transovarial transmission of dengue viruses in field populations of DHF vectors and elucidates circulation of dengue viruses in vectors in the natural environment of endemic areas. The incidence of multiple serotypes of dengue virus in Ae. aegypti and Ae. albopictus in the same area points toward a high risk for an epidemic of DHF. These findings provide greater understanding of the relationship among mosquito vectors, virus transmission and DHF epidemiology in endemic areas.     

Dengue viremia titer, antibody response pattern, and virus serotype correlate with disease severity

Viremia titers in serial plasma samples from 168 children with acute dengue virus infection who were enrolled in a prospective study at 2 hospitals in Thailand were examined to determine the role of virus load in the pathogenesis of dengue hemorrhagic fever (DHF). The infecting virus serotype was identified for 165 patients (DEN-1, 46 patients; DEN-2, 47 patients; DEN-3, 47 patients, DEN-4, 25 patients). Patients with DEN-2 infections experienced more severe disease than those infected with other serotypes. Eighty-one percent of patients experienced a secondary dengue virus infection that was associated with more severe disease. Viremia titers were determined for 41 DEN-1 and 46 DEN-2 patients. Higher peak titers were associated with increased disease severity for the 31 patients with a peak titer identified (mean titer of 107.6 for those with dengue fever vs. 108.5 for patients with DHF, P=.01). Increased dengue disease severity correlated with high viremia titer, secondary dengue virus infection, and DEN-2 virus type.     

Changing clinical and biological manifestations of dengue during the dengue-2 epidemic in French Polynesia in 1996/97 – description and analysis in a prospective study

In August 1996 dengue-2 virus was detected in French Polynesia for the first time since 1976. A prospective study was conducted from November 1996 to April 1997. Each time one of 7 physicians suspected dengue, the patient was enrolled and epidemiological, clinical and biological data were recorded. Dengue diagnosis was confirmed by virus isolation and IgM detection. The aims of this study were to find clinical and biological predictive factors constituting a specific profile of dengue (DF) and dengue haemorrhagic fever (DHF/DSS) and to assess the possibility of diagnosing dengue at primary health care level using clinical criteria and basic laboratory parameters. Of 298 clinically suspect cases, 196 (66%) were confirmed as dengue. The association of macular rash, pruritis, low platelet count and leukopenia was statistically predictive of dengue but not clinically, since these four signs occur in many other viral infections. As the prevalence of clinical and biological manifestations varied over time in our study, a specific profile useful for dengue diagnosis cannot be defined. With six cases of DHF, the morbidity of this dengue-2 outbreak was very low despite the sequential infection scheme DEN-3/DEN-2. The clinical expression of dengue could depend on a specific virus strain circulating in a specific population in a particular place, with varying virulence over time.     

Do escape mutants explain rapid increases in dengue case-fatality rates within epidemics?

During the Cuban dengue epidemics of 1981 and 1997, significant monthly increases were observed in the proportion of total cases that presented as dengue haemorrhagic fever or dengue shock syndrome (DHF/DSS), and in case-fatality rates for both dengue fever and DHF/DSS. We believe that theses increases can be explained by the hypothesis that some of the population of antibodies against dengue 1 virus raised after natural primary infections react with "neutralisation" determinants found on dengue 2 viruses. These heterotypic antibodies do not prevent secondary dengue 2 infections, but serve to down-regulate the disease to mild illness or symptomless infections. A population of dengue 2 viruses that replicates in dengue-1-immune hosts escape heterotypic neutralisation. When inoculated into a new dengue-1-immune host, these viruses are free to interact with the more abundant infection-enhancing antibodies to produce severe disease.     

Association between sex, nutritional status, severity of dengue hemorrhagic fever, and immune status in infants with dengue hemorrhagic fever

The association between sex, nutritional status, and the severity of dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS), and immune status was investigated in 245 Vietnamese infants with predominantly primary infections with dengue virus. Male and female infants were at equal risk of developing DHF/DSS. However, infants of low height and weight for age were under-represented among DHF/DSS cases compared with 533 healthy baby clinic infant controls. Acute illness phase blood levels of selected cytokines (interferon-gamma and tumor necrosis factor-alpha) and serum levels of antibodies to dengue virus were elevated in the same range in male and female infants with DHF/DSS, as well as in infants with and without malnutrition.     

Infections with two dengue viruses in Greece in the 20th century. Did dengue hemorrhagic fever occur in the 1928 epidemic?

From contemporary clinical accounts we hypothesized that the 1928 dengue epidemic in Greece may have been an earlier occurrence of dengue hemorrhagic fiver/dengue shock syndrome (DHF/DSS). To study the possibility that two different dengue viruses may have been involved, serums from 62 Athenians alive during the epidemic were examined for dengue antibodies; 73 per cent showed evidence of prior dengue infection. Monotypic neutralizing antibodies were found to two different dengue viruses, types 1 and 2. A large proportion of the sampled population had evidence of two or more past dengue infections. Since there is no evidence that dengue viruses have been transmitted in Greece since 1928, during the epidemic a very large number of persons immune to one dengue type must have acquired infections with a secon type. The virological criteria for secondary infection DHF/DSS are thus satisfied. Although DHF/DSS is currently restricted to Asia and the Pacific, the Greek oubreak suggests a biological potential for fatal consequences of dengue infections in Caucasians, particularly the elderly.     

Dengue

The four dengue viruses are transmitted in tropical countries that circle the globe. All can cause syndromes that are self-limited or severe. The common severe syndrome--dengue haemorrhagic fever/dengue shock syndrome (DHF/DSS)--is characterised by sudden vascular permeability generated by cytokines released when T cells attack dengue-infected cells. Dengue 1 virus became prevalent in Hawaii where it was transmitted by Aedes albopictus, producing a classic virgin soil epidemic, with clinical disease seen largely in adults. In Cuba and Singapore, sequential dengue infections at long intervals produced unusually severe disease in adults. Evidence suggests that enhancing and cross-reactive neutralising antibodies regulate dengue epidemics and disease severity. Classic DHF/DSS arises during initial dengue infections in infants with low circulating amounts of maternal dengue antibodies, an observation that precludes an exclusive causal role for secondary T-cell responses. Here, I review and discuss data on clinical diagnosis and pathophysiology of vascular permeability and coagulopathy, parenteral treatment of DHF/DSS, and new laboratory tests.     

Influence of the dengue serotype, previous dengue infection, and plasma viral load on clinical presentation and outcome during a dengue-2 and dengue-4 co-epidemic

Martinique experienced a dengue outbreak with co-circulation of DENV-2 and DENV-4. In an emergency department-based study, we analyzed whether the clinical presentation and outcome of adult patients were related to serotype, immune status, or plasma viral load. Of the 146 adult patients who had confirmed dengue infection, 91 (62.3%) were classified as having classic dengue fever, 11 (7.5%) fulfilled World Health Organization criteria for dengue hemorrhagic fever (DHF) or dengue shock syndrome (DSS), 21 other patients (14.4%) presented with at least one typical feature of DHF/DSS [i.e., internal hemorrhage, plasma leakage, marked thrombocytopenia (platelet count < or = 50,000 platelets/mm(3)) and/or shock], and 23 further patients (15.8%) had unusual manifestations. Four patients died. Severe illness was more frequent in patients with secondary dengue infection (odds ratio, 7.18; 95% confidence interval, 3.1-16.7; P < 0.001). Multivariate regression analysis showed that gastrointestinal symptoms and other unusual manifestations were independently associated with DENV-2 infection, whereas cough and DHF/DSS features were independently associated with secondary immune response. A high plasma viral load was associated with DENV-2 infection, increased serum liver enzymes, and with DHF/DSS features in patients presenting after the third day of illness. The most severe cases of dengue resulted from the combined effects of DENV-2 and secondary infection.     

Hospital based clinical surveillance for dengue haemorrhagic fever in Bandung, Indonesia 1994-1995

In Indonesia, by law dengue haemorrhagic fever (DHF) cases must be reported within 24 h to the district health authority. The objective of this study was to evaluate the adequacy, accuracy and reporting delay of this reporting system. In four major hospitals of the city of Bandung, medical records of hospitalised DHF cases admitted between April 1994 and March 1995 were reviewed. This list of DHF cases was compared with the list of reported cases to the Bandung Municipality Health Office. During the study period, 569 DHF cases and 81 dengue shock syndrome (DSS) cases were diagnosed. Only 199 (31%) of the 650 hospitalised cases with suspected DHF/DSS were reported to the Bandung Municipality Health Office. The percentage of fatal cases was significantly lower among all hospitalised cases 11/650 (1.7%) than among reported cases 5/199 (2.5%). In only 443 of the 583 hospitalised cases (76%) in which a dengue serological test was performed, was this test positive. Of the 199 reported DHF/DSS cases 151 (76%) had a positive haemagglutination inhibition test. This study shows that the surveillance system for DHF/DSS in Bandung should be strengthened. DHF/DSS cases should be reported on the basis of a diagnosis made during hospitalisation preferably after a serological confirmation is obtained.     

Dengue hemorrhagic fever in infants: a study of clinical and cytokine profiles

A prospective study of clinical and cytokine profiles of 107 infants with dengue hemorrhagic fever (DHF)/dengue shock syndrome (DSS) was conducted. Fever, petechiae on the skin, and hepatomegaly were the most common clinical findings associated with DHF/DSS in infants. DSS occurred in 20.5% of the patients. Hemoconcentration and thrombocytopenia were observed in 91.5% and 92.5% of the patients, respectively. Serologic testing revealed that almost all of the patients (95.3%) had primary dengue virus infections. These data demonstrate that clinical and laboratory findings of DHF/DSS in infants are compatible with the World Health Organization's clinical diagnostic criteria for pediatric DHF. The present study is the first to report evidence of production of cytokines in infants with DHF/DSS and to describe the difference between the cytokine profile of infants with primary dengue virus infections and children with secondary infections. Overproduction of both proinflammatory cytokines (interferon-gamma and tumor necrosis factor-alpha) and anti-inflammatory cytokines (interleukin-10 and -6) may play a role in the pathogenesis of DHF/DSS in infants.     

Fatal dengue hemorrhagic fever in Cuba, 1997.

OBJECTIVES: After more than 15 years without dengue activity, a dengue II epidemic was reported in Cuba in 1997. Three thousand and twelve serologically confirmed cases were reported, with 205 dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS) cases and 12 fatalities. This report presents the clinical, serologic, and virologic findings in the 12 fatal DHF/DSS cases. METHODS: Serum and necropsy samples were studied by viral isolation in C636 cell line and polymerase chain reaction. Serum samples were tested by IgM capture enzyme-linked immunoassay (ELISA) and ELISA inhibition method (EIM). RESULTS: All 12 cases were classified as DHF/DSS according to the Pan American Health Organization Guidelines for Control and Prevention of Dengue and Dengue Hemorrhagic Fever in the Americas. All patients were older than 15 years. Women were more frequently affected. The symptoms and signs presented by these patients were similar to those previously described in DHF/DSS cases. Clinical deterioration occurred on average at day 3.75. Abdominal pain and persistent vomiting were the earliest and most frequent warning signs. Dengue infection was confirmed in all cases. IgM antibodies were detected in 11 of 12 cases, all of them with a secondary infection. Dengue II virus was detected by viral isolation in 12 samples and by polymerase chain reaction in 17. Virus or RNA was detected in various tissues, including kidney, heart, lung, and brain. CONCLUSION: The clinical, pathologic, and laboratory features of 12 cases of fatal dengue hemorrhagic fever were reviewed. The results obtained demonstrate that adults with a primary dengue infection are at risk of developing the severe disease (DHF) if they are infected with a different serotype.     

Human immune responses to dengue viruses

Dengue fever (DF) and dengue hemorrhagic fever (DHF)/dengue shock syndrome (DSS) are major public health problems in many areas of the world. We are analyzing the human immune responses to dengue viruses, in order to understand the mechanism of recovery from dengue virus infections and the pathogenesis of DHF/DSS. Human natural killer (NK) cells lyse dengue virus-infected cells to a greater degree than uninfected cells. Antibodies to dengue viruses augment the lysis of dengue virus-infected cells by NK cells. Dengue virus-infected monocytes produce high levels of interferon alpha (IFN alpha). DR+ lymphocytes also produce high levels of IFN alpha after contact with dengue virus-infected monocytes. The IFN alpha produced protects uninfected monocytes from dengue virus infection. These results suggest that NK cells and IFN alpha may play an important role in controlling primary dengue virus infection. Dengue virus-specific CD4+CD8(-)T lymphocytes and CD4(-)CD8+T lymphocytes are present in the peripheral blood mononuclear cell population from donors who were infected with dengue virus. Most of CD4+T lymphocytes are dengue serotype-crossreactive. They lyse dengue virus-infected autologous cells in an HLA class II-restricted fashion, and produce interferon gamma (IFN gamma). IFN gamma augments dengue virus infection of monocytic cells in the presence of antidengue virus antibodies by increasing the number of Fc gamma receptors. Dengue virus-specific CD8+T lymphocytes lyse dengue virus-infected autologous cells in an HLA class I-restricted fashion. These CD8+T lymphocytes are also dengue serotype-crossreactive.(ABSTRACT TRUNCATED AT 250 WORDS)     

Serotype-specific dengue virus circulation and dengue disease in Bangkok,Thailand from 1973 to 1999

Dengue virus circulation and association with epidemics and severe dengue disease were studied in hospitalized children with suspected dengue at the Queen Sirikit National Institute of Child Health in Bangkok, Thailand, from 1973 to 1999. Dengue serology was performed on all patients and viral isolation attempted on laboratory-confirmed patients. Acute dengue was diagnosed in 15,569 children and virus isolated from 4,846. DEN-3 was the most frequent serotype in primary dengue (49% of all isolates), DEN-2 in secondary and in dengue hemorrhagic fever (37% and 35%, respectively). The predominant dengue serotype varied by year: DEN-1 from 1990-92, DEN-2 from 1973-86 and 1988-89; DEN-3 in 1987 and 1995-99; and DEN-4 from 1993-94. Only DEN-3 was associated with severe outbreak years. Our findings illustrate the uniqueness of each serotype in producing epidemics and severe disease and underscore the importance of long-term surveillance of dengue serotypes in understanding the epidemiology of these viruses.     

云南西双版纳州勐腊县一起登革热暴发疫情调查分析

目的分析云南省西双版纳州勐腊县2013年1起登革热暴发疫情的流行病学特征,为登革热控制提供依据。方法对所有登革热病例进行流行病学个案调查,疑似病例血清标本采用登革病毒NS1抗原法进行检测,用RT-PCR进行登革热病毒型别鉴定,采用布雷图指数法进行蚊媒密度监测。结果本次疫情流行历时35d,共发现病例44例,其中本地感染病例34例,输入性病例10例(景洪市7例、缅甸2例、老挝1例);病例主要集中在勐腊县城区,共28例,占63.64%(28/44);男女性别比为1.44:1,发病年龄最小4岁、最大75岁,以20~49岁年龄组为主,共33例,占75.00%;职业以农民、商业服务和家政及待业居多;共检出3个登革血清型(Ⅰ型、Ⅱ型和Ⅲ型),其中老挝输入病例为登革病毒Ⅱ型,缅甸输入病例为登革病毒Ⅰ型,其余为登革病毒Ⅲ型。结论该起疫情属于以登革病毒Ⅲ型为主,传播媒介白纹伊蚊和埃及伊蚊并存的暴发疫情。提示今后应进一步加强登革热输入病例的监测和蚊媒控制工作。     

Molecular characterization and clinical evaluation of dengue outbreak in 2002 in Bangladesh

During the febrile illness epidemic in Bangladesh in 2002, 58 people died out of the 6,132 affected. Two hundred hospitalized patients were analyzed clinically, serologically and virologically to determine the features of this dengue infection. Among the 10- to 70-year-old age group of the 200 clinically suspected dengue patients, 100 (50%) were confirmed as dengue cases by virus isolation and dengue IgM-capture ELISA. Of the 100 dengue-confirmed cases, the mean age was 29.0 (+/-12.4). The possible dengue secondary infection rate determined by Flavivirus IgG-indirect ELISA was 78% in 2002. Eight dengue virus strains were isolated, representing the first dengue virus isolation in the country, and all of the strains were dengue virus type-3 (DEN-3). Sequence data for the envelope gene of the DEN-3 Bangladeshi isolates were used in a phylogenetic comparison with DEN-3 from other countries. A phylogenetic analysis revealed that all 8 strains of DEN-3 were clustered within a well-supported independent sub-cluster of genotype II and were closely related to the Thai isolates from the 1990s. Therefore, it is likely that the currently circulating DEN-3 viruses entered Bangladesh from neighboring countries.