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Household survey of dengue infection in central Brazil: spatial point pattern analysis and risk factors assessment.

Urban dengue fever is now considered a major public health threat in most American countries. A household survey was conducted in the city of Goiania in central Brazil in 2001 to assess prevalence of dengue infection and individual and area-based risk factors. Spatial point pattern analysis was performed using the dual Kernel method. A total of 1,610 households were surveyed; 1,585 individuals more than five years old had blood and data collected. Sera were tested for IgM/IgG antibodies by an enzyme-linked immunoassay. Area-based indicators derived from census data were linked to geocoded residential address. The seroprevalence of dengue was 29.5% and the estimate prevalence surface reached 50% in the outskirts areas. The risk of infection was significantly associated with older age (P < 0.01), low education (odds ratio [OR] = 3.45, 95% confidence interval [CI] = 1.82-6.55), and low income (OR = 1.32, 95% CI = 1.02-1.71) in multivariate analysis. This study highlighted the heterogeneity of dengue transmission within the city and can assist in spatial targeting control interventions.

Adolescent↗

[The cloning and sequence analysis of cDNA of the partial E genomic region of Dengue type 4 virus from a Chinese patient].

The partial envelope (E) protein gene of Dengue virus type 4 (DV4), derived from the serum of a patient with dengue fever in an epidemic during October 1993 in Guangdong Province of China, was cloned and sequenced. DV RNA was converted to cDNA by reverse transcription with random primers before the polymerase chain reaction using DV4 specific primers was performed. The amplified product of 421bp was subsequently filled in 3' recessed ends, isolated, purified and inserted into pUC18 and pUC19 plasmid vector. Their sequences were determined by dideoxy nucleotide chain termination method. A comparison between DV4 Chinese strain and several other previously reported strains shows the homology to be 93.72% for the same dengue serotype, 61.26-64.40% for the other dengue serotypes, only 40.31% for Japanese encephalitis virus, which belongs to the member of flavivirus family. A conserved sequence with 12 amino acids observed from deduced protein sequence probably represents an essential functional element among flavivirus family.

Amino Acid Sequence↗

[Analysis of the E gene sequences of three dengue virus type 1 isolates in Guangdong province].

OBJECTIVE: To trace the infection sources of three dengue virus type 1 isolates found in Guangdong province, namely GD05/99, GD14/97 and GD23/95. METHODS: According to the genomes of dengue virus type 1 S275 strain, a pair of primers was designed for amplification of the structural protein E gene of the isolated dengue virus type 1 strains by reverse transcriptase-PCR. The amplified gene fragment was then cloned into pMD18-T vector and sequenced. RESULTS: GD14/97 and GD05/99 shared a high nucleotide homology with Cambodia (98% and 99% respectively) and may belong to the same genotype. GD23/95 had a 95% nucleotide homology with A88, higher than that with other strains. GD23\95 and A88 may belong to another genotype. CONCLUSION: The dengue fever outbreak in Guangdong during 1999, 1997, and 1995 may originate from the viruses from different countries.

Base Sequence↗

Elimination of dengue by community programs using Mesocyclops(Copepoda) against Aedes aegypti in central Vietnam.

From September 2000 to June 2003, a community-based program for dengue control using local predacious copepods of the genus Mesocyclops was conducted in three rural communes in the central Vietnam provinces of Quang Nam, Quang Ngai, and Khanh Hoa. Post-project, three subsequent entomologic surveys were conducted until March 2004. The number of households and residents in the communes were 5,913 and 27,167, respectively, and dengue notification rates for these communes from 1996 were as high as 2,418.5 per 100,000 persons. Following knowledge, attitude, and practice evaluations, surveys of water storage containers indicated that Mesocyclops spp. already occurred in 3-17% and that large tanks up to 2,000 liters, 130-300-liter jars, wells, and some 220-liter metal drums were the most productive habitats for Aedes aegypti. With technical support, the programs were driven by communal management committees, health collaborators, schoolteachers, and pupils. From quantitative estimates of the standing crop of third and fourth instars from 100 households, Ae. aegypti were reduced by approximately 90% by year 1, 92.3-98.6% by year 2, and Ae. aegypti immature forms had been eliminated from two of three communes by June 2003. Similarly, from resting adult collections from 100 households, densities were reduced to 0-1 per commune. By March 2004, two communes with no larvae had small numbers but the third was negative; one adult was collected in each of two communes while one became negative. Absolute estimates of third and fourth instars at the three intervention communes and one left untreated had significant correlations (P = 0.009-< 0.001) with numbers of adults aspirated from inside houses on each of 15 survey periods. By year 1, the incidence of dengue disease in the treated communes was reduced by 76.7% compared with non-intervention communes within the same districts, and no dengue was evident in 2002 and 2003, compared with 112.8 and 14.4 cases per 100,000 at district level. Since we had similar success in northern Vietnam from 1998 to 2000, this study demonstrates that this control model is broadly acceptable and achievable at community level but vigilance is required post-project to prevent reinfestation.

Aedes↗

Molecular epidemiology of dengue 2 viruses in the Philippines: genotype shift and local evolution.

The pre-membrane (prM) and envelope (E) genes of 41 viruses isolated from dengue fever (DF), dengue hemorrhagic fever (DHF), and dengue shock syndrome (DSS) patients from 1995 to 2002 were sequenced to determine the genetic variability of dengue 2 (DENV 2) viruses in the Philippines. The envelope sequence data were compared with a global sample of DENV 2 obtained from GenBank. Phylogenetic analysis revealed that two distinct genotypes, Asian 2 and Cosmopolitan, are currently circulating locally, each with the potential to cause severe hemorrhagic disease. After the initial isolation in 1998, the Cosmopolitan genotype has gradually and effectively replaced Asian genotype 2 in the Philippines. Members of this genotype were closely related to viruses from Australia, Singapore, and Thailand.

Animals↗

Serotype-specific differences in clinical manifestations of dengue.

Dengue, the most prevalent arthropod-borne viral disease of humans, is caused by four serotypes of dengue virus (DENV 1-4). Although all four DENV serotypes cause a range of illness, defining precisely which clinical characteristics are associated with the distinct serotypes has been elusive. A cross-sectional study was conducted on 984 and 313 hospitalized children with confirmed DENV infections during two time periods, respectively, in the same hospitals in Nicaragua: a 3-year period (1999-2001) when DENV-2 accounted for 96% of the viruses identified, and the 2003 dengue season when DENV-1 predominated (87% of identified serotypes). When the two periods were compared, more shock (OR 1.91, 95% CI 1.35-2.71) and internal hemorrhage (OR 2.05, CI 1.16-3.78) were observed in the period when DENV-2 predominated, whereas increased vascular permeability was associated to a greater degree with the DENV-1 period (OR 2.36, CI 1.80-3.09). Compared with the DENV-2 period, the DENV-1 season was associated with more hospitalized primary dengue cases (OR 3.86, CI 2.72-5.48) and more primary DENV infections with severe manifestations (OR 2.93, CI 2.00-4.28). These findings provide new data to characterize the pathogenic potential of distinct DENV serotypes in human populations.

Adolescent↗

[Construction and identification of genomic cDNA subclones of dengue 2 virus NGC strain].

OBJECTIVE: To construct the cDNA subclones spanning the entire genome of dengue 2 virus NGC strain for further construction of full-length infectious viral cDNA clone. METHODS: Two pairs of primers were designed according to the restriction endonuclease sites in the viral genome of dengue 2 virus NGC strain. After viral RNA extraction from the brain of infected new-born mice, two parts of full-length viral cDNA were amplified by long RT-PCR and cloned into the vector pCR-XL-TOPO. The partial sequence of the recombinant plasmid was determined. RESULTS AND CONCLUSION: Sequence analysis and digestion with restriction enzymes demonstrated that the two cDNA subclones were specific for dengue 2 virus NGC strain, suggesting the successful construction of the two cDNA subclones of dengue 2 virus NGC strain.

Animals↗

Molecular detection of dengue viruses in field caught Aedes aegypti mosquitoes from northeastern Argentina.

Most molecular protocols for Dengue virus detection described so far are time consuming and cumbersome with mosquito samples. In order to count with a sensitive and specific molecular detection system for monitoring possible Dengue outbreaks and circulating viral serotypes in field-caught Aedes aegypti populations from Northeastern Argentina, a RT-PCR and RFLP assay was developed. The original RT-PCR assay proposed by Sudiro et al. for human serum was optimized for mosquito samples. Modifications were done at the RNA extraction-purification and at the thermal profile steps. The generic 230 bp amplicon was validated by RFLP assay and cycle sequencing. Results showed that, due to the generic characteristic of the primers used, certain mosquito genome regions could be co-amplified, making confirmation of the Dengue specific amplicon by RFLP assay a required step. Under these conditions, the proposed method can be employed as a Dengue viral generic screening procedure in Aedes aegypti mosquito samples, giving in our hands an estimated 99.52% of confirmed negatives (207/208 tested samples).

Aedes↗

Clinical presentations and laboratory findings in suspected cases of dengue virus.

OBJECTIVE: To study the clinical presentations and laboratory findings of patients presented with fever in a Hospital in Portsudan, Sudan and to detect dengue virus antibodies in their blood. METHODS: This study was carried in Almwani Hospital during the period from April to July 2005. Eighty-four patients were included in this hospital-based study. All of them had fever. Their blood films, Widal tests for typhoid, stools and urine investigations were normal. The clinical data were collected using questionnaires. Two samples of blood were taken. One was for general hematological investigation (white blood cell and platelets count), while serum was taken from the other sample for serological detection of the dengue virus antibodies using the enzyme-linked immunosorbent assay (ELISA) technique. RESULTS: The fever was associated with vomiting (22 patients) and abdominal pain (44 patients). In 93% of the cases bleeding (epistaxes, purpura, malena, hematemesis, and others) occurred. Routine laboratory findings were leucopenia (90% of the cases) and thrombocytopenia (88% of the cases). The diagnosis was confirmed by ELISA detection of dengue virus immunoglobulin M antibodies (in 88% of the patient's sera). CONCLUSION: In endemic areas with mosquitoes such as Aedes aegypti, infection with dengue virus should highly be suspected in patients presented with fever. The ELISA or rapid tests for detection of the viral antibodies should be added to the routine investigations to any patient with complain of fever with no obvious cause. Surveillance program and mosquito control measures should be activated in Portsudan.

Adolescent↗

[Effects of Dengue virus infection on PGIS expression and PGI2 secretion of human vascular endothelial cells].

AIM: To elucidate the effects of Dengue virus on the expression and secretion of prostacyclin (PGI(2)) in endothelial cells. METHODS: Cultured human umbilical vein endothelial cells (HUVEC) were infected by Dengue virus II(DV(2)) for different duration. PGI(2) level in the supernatant was determined by radioimmune assay. Cytoplasmic RNA of the infected HUVEC was prepared using the Trizol method and was assayed for prostacyclin synthase (PGIS) by RT-PCR. RESULTS: PGIS expression as well as PGI(2) secretion of the DV(2) group were significantly increased (P<0.05) at 48 h, 72 h and 96 h post-infection compared to the control group. CONCLUSION: DV(2) could promote the expression of PGIS mRNA in HUVEC and increase the level of PGI(2), which may increase the vascular permeability. The dysfunction of vascular endothelial cell (EC) induced by DV may be related to the pathogenesis of Dengue haemorrhagic fever (DHF) and Dengue shock syndrome(DSS).

Cells, Cultured↗

An insular outbreak of dengue fever in a rural south Indian village.

In mid 1990, an epidemic of fever affected a single village in Kaniyambadi Block, South India. The illness was characterized by a fever of approximately five days duration, accompanied by headache, chills, sweating and muscle pain. The overall attack rate was 22.5 per cent. The attack rate was uniform across the various age groups and between the sexes. Testing of the acute and convalescent serum samples obtained from cases showed a serological response to dengue virus. The Aedes house index in the village was found to be 36 per cent with toilets serving as active breeding sites. Adjacent villages studied showed similarly high rates of Aedes prevalence, although no cases of the same fever were seen. Since previous exposure to dengue increases the risk for epidemics of dengue hemorrhagic fever and dengue shock syndrome, health education on methods of Aedes control is continuing.

Adolescent↗

[Reappearance of dengue in New Caledonia from 1985 to 1988].

From 1971 to 1980, dengue outbreaks occurred in New-Caledonia due to dengue viruses type 2, 1 and 4 successively. After an eclipse of four years, dengue reappeared in 1985 through 1988. Out of 109 cases confirmed by virus isolation, dengue serotypes 1, 2, 3 and 4 caused 15, 23, 17 and 54 cases respectively; in 28 other cases, the Flavivirus type could not be identified and in 26 cases an Alphavirus (Ross River) was pointed out. The DEN 3 virus, unknown in New-Caledonia before 1985, was discretely transmitted until 1988. The 1989 outbreak showed the necessity of rigorous vector control measures.

Aedes↗

Clinical & virological study of dengue fever outbreak in Jalore city, Rajasthan 1985.

An epidemic of acute febrile illness caused by dengue virus occurred in Jalore town, in south-west Rajasthan, in April and May, 1985. Most patients had classical signs and symptoms of dengue fever or had only a mild atypical febrile illness. A few patients had in addition haemorrhagic manifestations/shock or encephalitis. Virological studies (carried out by the National Institute of Virology, Pune) showed that dengue type 3 virus was the main etiological agent. This is the first reported outbreak of dengue in the arid zone in western Rajasthan, that occurred in summer (April-May) in contrast to other parts of India, where such outbreaks are commonly reported after the rains (between August and November).

Adolescent↗

[Epidemic dengue 2 on Liouchyou Shiang, Pingtung County in 1981].

During the summer of 1981, an outbreak of dengue occurred on Liouchyou Shiang, an islet about 15 km. southwest of Taiwan. More than 12, 500 people, approximately 80% of the inhabitants, were estimated to be affected in this epidemic which had been the first dengue outbreak in Taiwan since 1945. Neither shock nor fatal case was found. The epidemic subsided in October and there was no confirmed dengue case in Taiwan from 1982 to 1985. All the 21 virus strains isolated from the blood of patients were now identified as type 2 dengue virus and believed to be the first isolation in Taiwan. The pathogen was probably introduced from the Philippines.

Adolescent↗

[Dengue in Burkina Faso (ex-Upper Volta): seasonal epidemics in the urban area of Ouagadougou].

During the rainy season of 1982 30 patients (29 european and 1 voltaic) presented with an intense dengue-like syndrome in Ouagadougou city. 73.3% of these cases possessed anti-flavivirus fluorescent antibodies while 30%, were positive for specific anti-Dengue IgM antibodies. Vero type E 6 cell cultures were used to isolate six strains of Dengue 2 virus; monoclonal antibodies were used for viral identification. These strains constitute the first isolates of human Dengue virus in Upper Volta. Authors present conditions of virus isolations, describe the observed syndrome and discuss the epidemiological interest of this outbreak.

Adolescent↗

Dengue virus isolation in Indonesia, 1975-1978.

Virus isolations from dengue hemorrhagic fever patients in Indonesia are reported from 1975 to 1978. All 4 dengue serotypes were endemic in Jakarta, but dengue 3 was the predominant virus isolated. This type was also the most frequently isolated virus from patients outside Jakarta and had the widest distribution in Indonesia. The sensitivity of the mosquito inoculation technique for isolation of dengue viruses is discussed.

Antigens, Viral↗

A retrospective serological study of Japanese who contracted dengue fever in Thailand.

Between September and November 1981, some members of a survey team from Japan suffered from a febrile illness diagnosed clinically as dengue fever during their stay in a village in Khon-Kaen Province, in the north-eastern part of Thailand. The morbidity rate in the team was as high as 69% (11/16). Blood samples were taken from 12 of the 16 members of the team in February, 1982 in Japan and the serum specimens were examined for antibodies to dengue (DEN), Japanese encephalitis (JE) and yellow fever (YF) viruses respectively. The results of the tests indicated that all 8 members who had had symptoms had been infected with DEN type 1 virus. No case of inapparent infection with dengue viruses was found. Of these 8 persons, seven had had neutralizing (N) antibody to JE virus before infection, but their clinical manifestations had been similar to those of an individual without N antibody to JE virus and were typical symptoms of dengue fever, such as leukopenia and "saddle-back" fever, without hemorrhagic manifestations, as seen from platelet counts and hematocrit values.

Adult↗

An outbreak of type 2 dengue fever in the Seychelles, probably transmitted by Aedes albopictus (Skuse).

Between December 1976 and September 1977 the Seychelles group of islands in the Indian Ocean was struck by an extensive epidemic of dengue fever. The peak of the epidemic was in the last week of February. Type 2 dengue virus was isolated from patients and mosquitos. Aedes albopictus was the sole vector. The clinical picture was that of classical dengue. Haemorrhagic fever and the shock syndrome were not observed.Absenteeism from schools and offices, anamnestic questioning, and prevalence of antibodies in sera collected after the epidemic was over, indicated that approximately 75% of the population had been infected. Serological evidence was obtained of an epidemic of dengue in the islands more than 40 years earlier. This was confirmed by archival records.

Adolescent↗