Molecular epidemiological and serological studies of hantavirus infection in northern Vietnam.

The distribution of anti-hantavirus antibodies in humans and rodents in northern Vietnam was examined. In total, 837 serum samples from healthy humans (617) and patients with fever (220), living in six different areas were screened for IgG antibodies against Hantaan or Seoul virus (SEOV) by ELISA, IFA, and Western blot analysis. Antibody-positive sera were identified in 7/617 (1.1%) healthy donors, 5/150 port workers in the port of Hai Phong, and 2/185 residents of Ha Nam Province. In comparison, positive sera were detected in 5/220 (2.3%) fever patients in the provinces of Ha Nam (1/58) and Thanh Hoa (4/146). Antibody-positive Rattus norvegicus were found in the provinces of Ha Nam (7/52) and Thanh Hoa (1/67), in Haibatrung District (7/43) in Hanoi, and in Hai Phong Port (21/62), while antibody-positive R. rattus (2/17) were found in Hai Phong Port. Part of the Gc region from the viral genome was amplified by RT-PCR using lung tissue samples from R. norvegicus in Haibatrung (2/7) and Hai Phong Port (7/9), but not from R. rattus (0/2). Viral sequences were located in the SEOV clade and formed a single lineage with Indonesian SEOV, suggesting that Vietnamese SEOV is part of a distinct lineage among Asian SEOVs.

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.

Expression of domain-3 envelop protein of Dengue virus type 2 in Escherichia coli

Envelope protein (E) of Dengue virus is an important antigen for immune response of Dengue virus, in which domain 3 (E3) encodes important specific epitopes of each serotype of the virus. It would be of a great value to express domain 3 and apply the recombinant proteins for development of the kit for DF/DHF diagnosis. The domain 3 of the gene coding for the envelope protein of dengue virus type 2 was amplified by PCR with primer pair that hangs BamHI and Xhol restriction sites at the 5 prime of the forward and reverse primer, respectively. The template for domain-3 amplification was the gene encoding preM-E protein that had been cloned and sequenced before. The amplified region of the gene was then inserted into the pET-TRX Fusion Expression Vector System with BamHI and Xhol restriction sites and transformed into E. coli BL21 DE3 Star. Recombinant protein D2E3 was expressed in a fusion form with Thioredoxin and His-Tag after induction with ImM IPTG. Recombinant D2E3 was purified with ProBond Nickel-Chelating Resin column (Invitrogen) and the purified recombinant D2E3 protein was used to check the reaction with the antibodies against native dengue antigens in the patient's sera by ELISA, Western blot and Dot blot. The results showed that, recombinant D2E3 protein of Dengue virus type 2 could react specifically with antibodies in the patient's sera.

Result of serological and virological surveillance of Dengue fever/Dengue haemorrhagic fever in the Northern Vietnam, 2003

In the year 2003, 525 specimens seem to be infected with Dengue fever/Dengue haemorrhagic fever in the Northern Vietnam were sent to the National Institute of Hygiene and Epidemiology, those specimens with IgM, IgG antibodies against Dengue virus was 85 cases (16.2%). In 2003, the number of Dengue fever/Dengue haemorrhagic fever was sporadic distributed in some provinces. Owing to active prevention of Dengue fever/Dengue haemorrhagic fever, so Dengue virus type 2 discovered early in Ha Tay, Thanh Hoa, Nghe An and Tay Nguyen provinces; Dengue virus type 1 in Ha Noi, Nghe An, Tay Nguyen provinces and Dengue virus type 4 in Ha Tinh, Thanh Hoa, and Tay Nguyen provinces

Serological study of Hantavirus in worker of Hai Phong port at 2003

In the year 2003, for Hantaan virus, a serological surveillance ELISA method was performed on 155 serum samples collected from the workers of Haiphong port.26/155 samples were positive or in suspect with rodent sera. The samples submitted to 2nd examen by indirect fluoresceine immuno-assay showed that 3/26 samples were positive 3 positive samples were undertaken further studies by WB technique with specific SEO antigenes ,which confirmed anti-hantaan virus (IgG) and nuclecapsid protein (NP) of51 kD weigt. Results showed that Hantaan virus was found among Haiphong port workers

Situation Dengue fever/Dengue haemorrhagic fever in Ha Noi, Nam Dinh, Thanh Hoa, Nghe An provinces, 1996 - 2001

Serum samples from patients with Dengue hemorrhagic fever were collected at the hospitals of Hanoi,Namdinh,Thanhhoa and NgheAn in 1995-2001 year period were investigated.The number of suspected patients with Dengue hemorrhagic fever was varied during the years, the highest in the year 1995, 1998, then decreased progressively to 2001. In 2 years of 1995-1996 period and 1998-2001 period 4 types of epidemiologic virus were found. The highest number of isolated samples was 54 in the year 1996, then1998. The endemic types varied obviously by years

Occurrence of dengue serotypes in northern Viet Nam, 1999-2001

In the period of 1999 - 2001, there were some outbreaks of dengue fever (DF) and dengue hemorrhagic fever (DHF) in North Vietnam. From 185 blood samples collected from clinically suspected patients at National Institute of Epidemiology, there were 47 positive. By indirect immunofluorescent assay with monoclone antibiotics, 18 samples (38.3%) were identified as dengue virus of type I, 9 samples (19.2%) dengue virus of type II, 20 samples (42.6%) dengue virus of type IV. There was not dengue virus of type III

Surveillance of dengue fever/dengue haemorrhagic fever in three provinces of central region of Vietnam, 2000-2002

The surveillance of Dengue fever/Dengue hemorrhagic fever was conducted in 3 provinces Khanh Hoa, Quang Ngai, Quang Nam (Central Vietnam) during 2000-2002 year period. In terms of serology, virology, an active surveillance network was established involving all health stations, the relating institute, the Department of preventive medicine and MOH, using the standard MAC-ELISA bio-kit of National Institute of Hygien and Epidemiology. No case of the disease was reported, while in surrounding areas, cases were detected. MAC-ELISA kit has had high fidelity, giving quick results

Some observations on dengue fever/ dengue hemorshagic fever in some provinces year 2003 through serological virological surveillance

Serum samples from patients with Dengue fever/dengue hemorrhagic fever (DF/DHF) were collected and sent to the Central Institute of Hygiene and Epidemiology in the year 2003. The analysis showed that Dengue virus of type 2 circulated in Ha Tay, Thanh Hoa, Nghe An and Tay Nguyen. In Thanh Hoa, Nghe An, Ha Noi, there were 2 types concurrently and in Tay Nguyen, 3 types of Dengue virus. Results of serological surveillance were reliable because they were detected by provincial laboratories and verified by the Department of Dengue virus of the Central Institute of Hygiene and Epidemiology

Senological observation on the posibility of existance of Hantaan virus endemic in rat and human in some localities of North Vietnam, year 2000

In the year 2000, 443 samples of human serum and 131 samples of serum of rodents were assayed by ELISA. Results showed that there were 2.0% of human sera and 2.0% of rodent sera positive with hantaan virus. These preliminary results suggested that Hantaan virus can be the causal factor of hemorrhagic fever in human and in rat

Some types of Dengue virus in Viet Nam from 1987 to 2002

In 1987-2002 period 1444/9660 samples (14.9%) of Dengue virus were isolated. Type 1 of Dengue virus appeared from 1989 to 1996. type 2 from 1987-1997, type 3 from 1996-1998, and type 4 recently. Gene structure of Viet Nam isolated virus in the year 1987 was similar to those in the world and in Jamaica and type 3 virus in the year 1988 was similar to that of Thailand 1987. The most of human virus isolated from adult were in the North, while in the South mainly at the age of 5-14 (60.28%)