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.     

Dengue activity in Puerto Rico during an interepidemic period (1995-1997).

From 1995 to 1997 dengue was reported in Puerto Rico at an average annual rate of 1.75/1,000 population, compared to 6.73 in 1994, an epidemic year. Dengue virus serotypes 1 (DEN-1), -2, and -4 were isolated each year, with DEN-2 predominating in 1995 and 1996, and DEN-4 in 1997. From 1995 through 1997 incidence was highest (0.61-0.77/1,000) in persons under 30 years of age; males and females were equally affected. Among positive cases, 28.3% to 37.9% were hospitalized; 28.9% to 35.2% had hemorrhagic manifestations; at least 1.1% to 1.6% fulfilled the criteria for dengue hemorrhagic fever/dengue shock syndrome; and 0.2% to 0.3% died. Neither hurricane preparations (1995) nor widespread floods (1996) seem to have affected dengue incidence. Most municipalities with the highest laboratory-diagnosed dengue rates in 1995 were in the eastern foothills of the central mountains, an area relatively spared by the 1994 epidemic. In the next two years, at least half of the municipalities with the highest laboratory-diagnosed dengue rates were in the west. The most intense municipal outbreak of this period (DEN-2, Villalba, 1995, rate of 11.67/1,000) is described to highlight the importance of local conditions and epidemiologic history in determining the risk of dengue.     

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.     

Dynamics of dengue virus circulation: a silent epidemic in a complex urban area

Serotypes of dengue DEN-1 and DEN-2 have been reported in much of Brazil over the last 15 years, and DEN-3 serotype was only recently detected. This prospective study was conducted in Salvador, a large city in north-east Brazil, where two epidemics were previously recorded (DEN-1 and DEN-2). We obtained the seroprevalence and 1-year incidence of dengue infections in the population of 30 sampling areas of Salvador and analysed the relationship between intensity of viral circulation, standard of living and vector density. High seroprevalence (68.7%) and annual incidence (70.6%) of infection for one or both circulating serotypes (DEN-1 and DEN-2) were found. High rates of transmission were observed in all studied areas, from the highest to the lowest socio-economic status. The mean PI (Premise Index) for Aedes aegypti was 7.4% (range 0.27-25.6%). Even in the areas with the lowest PI (相似文献   

Detection of dengue infection in patients investigated for leptospirosis in Barbados

The annual incidence of leptospirosis in Barbados is approximately 13 severe cases/100,000. The peak incidence occurs in October to December of each year, coinciding with the months of heaviest rainfall. During the second half of 1995, an epidemic of dengue type 1 infection produced almost 1,000 laboratory-confirmed cases. During the same period, leptospirosis mortality was twice the average, suggesting that some cases of leptospirosis were being misdiagnosed and treated inappropriately. Sera from patients investigated for dengue or leptospirosis were analyzed retrospectively to determine the extent of misdiagnosis. During 1995 and 1996, 31 of 139 and 29 of 93 patients, respectively, were confirmed as having leptospirosis. Sera from the remaining leptospirosis-negative patients were tested for IgM antibodies to dengue virus. During 1995 and 1996, 48 of 108 patients and 21 of 64 patients, respectively, were found to have dengue. In 1997, sera from all patients investigated for leptospirosis were also tested prospectively for IgM antibodies to dengue: 38 of 92 leptospirosis-negative patients (41%) were dengue IgM-positive, while 2 of 25 leptospirosis cases also had serologic evidence suggesting acute dengue infection. A second large outbreak of dengue caused by serotype 2 occurred in 1997. During the 1995 and 1997 dengue epidemics in Barbados, dengue cases outnumbered leptospirosis cases investigated in the leptospirosis diagnostic protocol. During 1997, patients investigated but negative for dengue were also tested for anti-leptospiral IgM: 7.3% (19 of 262) were IgM-positive. Substantial misdiagnosis of both dengue and leptospirosis can occur and greater public awareness and clinical suspicion of the similar presentations of these two diseases are necessary.     

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.     

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.     

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.     

2014—2020年上海市松江区登革热流行病学特征分析

目的    分析上海市松江区登革热流行病学特征,为登革热防治提供科学依据。方法    通过国家疾病监测信息报告管理系统获得2014—2020年松江区登革热病例信息,用描述性流行病学方法分析病例的发病时间、空间、人群分布等流行病学特征。结果    2014—2020年松江区累计报告登革热病例20例,均为输入性病例,无本地病例发生;无死亡病例。主要来自东南亚,占所有报告病例的95.0%（19/20）。时间分布呈单峰,以7—8月为高峰。男女性别比为4[∶]1,发病年龄中位数37岁,以青壮年为主（65.0%）。职业以公司职员（35.0%）、商业服务人员（20.0%）和工人（20.0%）为主。全区15个街道（镇）中7个有登革热病例报告。20例病例发病到确诊的时间间隔中位数为6 d。实验室检测检出DENV-1型和DENV-2型,以DENV-2型为主（71.4%）。结论    上海市松江区登革热疫情以输入性病例为主,有明显的季节性。登革热疫情防控的重点是严防输入,控制本地疫情的发生与流行。     

Efficiency of dengue serotype 2 virus strains to infect and disseminate in Aedes aegypti

Dengue serotype 2 (DEN-2) viruses with the potential to cause dengue hemorrhagic fever have been shown to belong to the Southeast (SE) Asian genotype. These viruses appear to be rapidly displacing the American genotype of DEN-2 in the Western Hemisphere. To determine whether distinct genotypes of DEN-2 virus are better adapted to mosquito transmission, we classified 15 viral strains of DEN-2 phylogenetically and compared their ability to infect and disseminate in different populations of Aedes aegypti mosquitoes. Envelope gene nucleotide sequence analysis confirmed that six strains belonged to the American genotype and nine strains were of the SE Asian genotype. The overall rate of disseminated infection in mosquitoes from Texas was 27% for the SE Asian genotype versus 9% for the American genotype. This pattern of infection was similar in another population of mosquitoes sampled from southern Mexico (30% versus 13%). Together, these findings suggest that Ae. aegypti tends to be more susceptible to infection by DEN-2 viruses of the SE Asian genotype than to those of the American genotype, and this may have epidemiologic implications.     

Epidemic dengue and dengue hemorrhagic fever at the Texas-Mexico border: results of a household-based seroepidemiologic survey, December 2005

A dengue-2 epidemic causing dengue hemorrhagic fever (DHF) occurred in the contiguous border cities of Matamoros, Tamaulipas (Mexico), and Brownsville, TX, in 2005. In December, we conducted a household-based epidemiologic survey to determine the incidence and seroprevalence of dengue infection among Matamoros and Brownsville residents and to identify risk factors associated with infection. Antibodies to dengue were measured in 273 individuals. The estimated incidence of recent dengue infection was 32% and 4% among Matamoros and Brownsville participants, respectively. The estimated prevalence of past dengue infection was 77% and 39% among Matamoros and Brownsville participants, respectively. The Breteau index was 28 in Matamoros and 16 in Brownsville, reflecting an abundant winter population of Aedes mosquitoes. Discarded waste tires and buckets were the two largest categories of infested containers found in both cities. Our results underscore the risk for epidemic dengue and DHF in the Texas-Mexico border region.     

Type-3 dengue viruses responsible for the dengue epidemic in Malaysia during 1993-1994.

To characterize the dengue epidemic that recently occurred in Malaysia, we sequenced cDNAs from nine 1993-1994 dengue virus type-3 (DEN-3) isolates in Malaysia (DEN-3 was the most common type in Malaysia during this period). Nucleic acid sequences (720 nucleotides in length) from the nine isolates, encompassing the precursor of membrane protein (preM) and membrane (M) protein genes and part of the envelope (E) protein gene were aligned with various reference DEN-3 sequences to generate a neighbor-joining phylogenetic tree. According to the constructed tree, the nine Malaysian isolates were grouped into subtype II, which comprises Thai isolates from 1962 to 1987. Five earlier DEN-3 virus Malaysian isolates from 1974 to 1981 belonged to subtype I. The present data indicate that the recent dengue epidemic in Malaysia was due to the introduction of DEN-3 viruses previously endemic to Thailand.     

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.     

Effect of temperature on the vector efficiency of Aedes aegypti for dengue 2 virus

The effect of temperature on the ability of Aedes aegypti to transmit dengue (DEN) 2 virus to rhesus monkeys was assessed as a possible explanation for the seasonal variation in the incidence of dengue hemorrhagic fever in Bangkok, Thailand. In two laboratory experiments, a Bangkok strain of Ae. aegypti was allowed to feed upon viremic monkeys infected with DEN-2 virus. Blood-engorged mosquitoes were separated into two groups and retained at constant temperatures. Virus infection and transmission rates were determined for Ae. aegypti at intervals ranging from 4 to 7 days during a 25-day incubation period. Results of the first experiment for mosquitoes infected with a low dose of DEN-2 virus and maintained at 20, 24, 26, and 30 degrees C, indicated that the infection rate ranged from 25% to 75% depending on the incubation period. However, DEN-2 virus was transmitted to monkeys only by Ae. aegypti retained at 30 degrees C for 25 days. In the second experiment, the infection rate for Ae. aegypti that ingested a higher viral dose, and incubated at 26, 30, 32, and 35 degrees C ranged from 67% to 95%. DEN-2 virus was transmitted to monkeys only by mosquitoes maintained at greater than or equal to 30 degrees C. The extrinsic incubation period was 12 days for mosquitoes at 30 degrees C, and was reduced to 7 days for mosquitoes incubated at 32 degrees C and 35 degrees C. These results imply that temperature-induced variations in the vector efficiency of Ae. aegypti may be a significant determinant in the annual cyclic pattern of dengue hemorrhagic fever epidemics in Bangkok.     

Genetic heterogeneity of the dengue vector Aedes aegypti in Martinique

In Martinique, Aedes aegypti, the vector of dengue viruses has been the target of insecticide control for more than 35 years. Despite significant control efforts, dengue has become a major disease of public health concern. We conducted a population genetic analysis based on isoenzyme variations combined with an estimation of infection rate to a dengue virus among 26 Ae. aegypti samples. Aedes aegypti samples could be differentiated for their susceptibility to dengue infection (infection rates ranging from 42.8% to 98.6%) and showed important genetic variation (significant F(ST) values).     

Temporal patterns and forecast of dengue infection in Northeastern Thailand

This study aimed to determine temporal patterns and develop a forecasting model for dengue incidence in northeastern Thailand. Reported cases were obtained from the Thailand national surveillance system. The temporal patterns were displayed by plotting monthly rates, the seasonal-trend decomposition procedure based on loess (STL) was performed using R 2.2.1 software, and the trend was assessed using Poisson regression. The forecasting model for dengue incidence was performed in R 2.2.1 and Intercooled Stata 9.2 using the seasonal Autoregressive Integrated Moving Average (ARIMA) model. The model was evaluated by comparing predicted versus actual rates of dengue for 1996 to 2005 and used to forecast monthly rates during January to December 2006. The results reveal that epidemics occurred every two years, with approximately three years per epidemic, and that the next epidemic will take place in 2006 to 2008. It was found that if a month increased, the rate ratio for dengue infection decreased by a factor 0.9919 for overall region and 0.9776 to 0.9984 for individual provinces. The amplitude of the peak, which was evident in June or July, was 11.32 to 88.08 times greater than the rest of the year. The seasonal ARIMA (2, 1, 0) (0, 1, 1)12 model was model with the best fit for regionwide data of total dengue incidence whereas the models with the best fit varied by province. The forecasted regional monthly rates during January to December 2006 should range from 0.27 to 17.89 per 100,000 population. The peak for 2006 should be much higher than the peak for 2005. The highest peaks in 2006 should be in Loei, Buri Ram, Surin, Nakhon Phanom, and Ubon Ratchathani Provinces.     

A realistic age structured transmission model for dengue hemorrhagic fever in Thailand

The influence of age structure in the susceptible class of the Susceptible-Infected Recovered (SIR) model used to describe the transmission of dengue hemorrhagic fever (DHF) was studied. This was done by first dividing all of the population classes into cohorts and then writing a set of coupled SIR equations for each cohort. The consequences of assuming different behavior of the transmission rates on the age structure in the DHF incidence rates were determined. In order for the predicted incidence rates to be similar to the DHF incidence patterns observed in several provinces in Thailand during the DHF epidemic in 1998, the transmission rates should be age dependent.