During the 1998 Japanese Encephalitis epidemic in Northern Vietnam the authors have examined 402 patients which were clinically diagnosed as "acute encephalitis syndrome". The IgM anti JE was evidenced in only 132 cases. The seropositivity is patients under 5 years of age was 33.0 - 42.1% in 1998, compared with 64.2 - 75.7% during the period of 1989 - 1995.
Encephalitis, Japanese ; Encephalitis Viruses, Japanese ; Serologic Tests

Particle agglutination assay (PA) was developed and applied for detecting specific IgM antibodies to Japanese encephalitis virus in recent years. In this study, the sensitivity of PA and MAC-ELISA were 91.11 and 97.77%, respectively
Encephalitis, Japanese ; Encephalitis Viruses, Japanese ; diagnosis

In 2004, 13 mosquito samples and 31 pig blood samples were collected at reveral districts, Gia Lai province for virus isolating. Isolating virus was carried out by Aedes albopictus clone C6/36 cells. Identifying virus was implemented by RT-PCR with generate primers of Alpha, Bunya, Flavi viruses and specific primers of Japanese encephalitis and Nam dinh virus. Result: one Japanese encephalitis virus strain was isolated from pig blood samples at Ia Grai, Gialai and six Nam dinh virus strains were isolated from Clux tritaeniorhynchus, Culex vishnui and Culex gelidus at Chu se, Gia Lai.
Encephalitis, Japanese ; Viruses

During 2003 - 2004, in total 976 sera and cerebrospinal fluid samples from patients with acute encephalitis syndrome (AES) were collected from Pediatric Hospital, several Centers of Preventive Medicine and National Institute of Hygiene and Epidemiology, Tay Nguyen for screening viral pathogens cause AES using MAC-ELISA with Japanese encephalitis (JE), West Nile and Nam Dinh virus antigens. Results: Out of 976 sera and cerebrospinal fluid samples of AES patients were screened using JE virus antigen, 46.1% (454/976) cases were confirmed to be JE virus infection. Out of 239 cerebrospinal fluid samples of AES patients were screened by Nam Dinh virus antigen, 13.4% (32/239) cases were confirmed to be Nam Dinh virus infection. Out of 103 sera and cerebrospinal fluid samples of AES patients were screened by West Nile virus antigen, there were no positive result was confirmed with this antigen. To date, JE virus is leading cause of AES in Vietnam, with over 80% cases in children under 15 years old. It should be intensive JE vaccination for all children under 15 years old in order to control JE soon.
Encephalitis, Japanese, West Nile virus

From 2000ml supernatant fluid of infected Aedes albopictus cells clone C6/36, Nam Dinh virus antigen was prepared by ultracentrifuge generating 5ml purified antigen. Protein content of the purified antigen is 4.4 mg/ml and antigen titer stabilizes for two years at - 80oC. The purified antigen was used for detecting IgM against Nam Dinh virus in cerebrospinal fluid from acute encephalitis syndrome patients by indirect IgM-ELISA. The examination of 814 cerebrospinal fluid samples of acute encephalitis syndrome, which were confirmed non-Japanese encephalitis during 1998 - 2004. The positive proportion with Nam Dinh virus antigen has been found to be 6.59 % - 20.06%. Most of positive cases in children were under 15 years old. Acute encephalitis syndrome cases due to Nam Dinh virus mainly occurred in May, June and July, in the same season of Japanese encephalitis in the Northern area of Vietnam.
Antigens ; Encephalitis ; Viruses ; Diagnosis

In the year 2002, a new arbovirus strain coded 02VN208 was isolated from cerebro- spinal fluid of patients with acute encephalitis syndrom by C6/36 mosquito cell lines. It’s a virus of 50nm spherical enveloped shape with ARN genetic materia. From a part of the extended sequence,specific primer pair was designed for determining the virus strains of the patients and the mosquitoes isolated by RT-PCR . 6 viral strains belonging to the same genotype of 02VN208 viral strain were confirmed. Results suggested that it’s a new arbovirus named Namdinh virus. Further study should be developed serologically and ultra morphologically
Encephalitis ; Viruses ; diagnosis ; Cerebrospinal Fluid ; epidemiology

Haemagglutination Inhibition Technique was applied to study conversion anti-Japanese encephalitis (JE) virus antibodies in pigs in Hoai Duc, Ha Tay, in 2002. The results showed that antibody conversion in pigs occurs year-round. Vero and C6/36 cells were used to isolate JE virus. From 83 mosquito pools and 30 pig blood samples, 7 JE viruses strains were isolated from mosquito pools, and 4 JE viruses strains were isolated from pig blood samples. These JE viruses strains were isolated either in the epidemic or in the non epidemic season. Sequencing of E gene region of JE virus strains that were isolated from mosquitoes and pigs, circulating of genotype I of JE virus in North Vietnam in 2002
Encephalitis Virus, Japanese ; Encephalitis Viruses ; Encephalitis ; Viruses

From 2001 September to 2002 August, 566 serum samples of 5-6 months pig at Hoai Duc district, Ha Tay province were supervised. Results showed very high frequency of JE infection among pig population during epidemic season with the percentage of positivity was 82% in June. By contrast during another months of non-epidemic season, the frequency of JE infection among pig population was very low, with the percentage of positivity was between 1.96% and 14%
Encephalitis, Japanese ; Serum ; Encephalitis

In September – December 2001 period, from 4987 female Culex mosquitoes collected in Cat Que commune, Hoai Duc district, Ha Tay province, 4 viral species were isolated by clone C6/36 cells of Vero and Aedes albopictus. Among them, 2 species were alpha virus, 01VN61 virus was isolated from Culex tritaeniorhynchus and 01VN62 virus from Culex gelidus, both strains were adapted to 1-2 days age mice. By sequencing technique on E1 gene and 3 NCR gene area, 01VN62 virus was identified as Safiyama virus, a virus of alpha virus
Alphavirus ; Culicidae ; Culex

453 cases of acute encephalitis syndrome were studied in the year 2002 at the National Institute of Pediatrics and 21 provinces of North Vietnam. Using Aedes albopictus clone C6/36, from CSF, 6 strains of Japanese encephalitis virus were isolated. By ELISA – Sandwich technique and indirect immunofluorescent assay, 4 virus strains were determined, including 4 strains of JE virus and 2 unknown viruses. 43.26% of cases of acute encephalitis syndrome were caused by JE virus. JE incidence in children of 1-4 years old reduced from 37.62% in 1989-1995 year period to 11.22% in 2002, due to the intensive immunization for children 1-5 years old.
Encephalitis, Japanese ; Encephalitis ; Diseases ; epidemiology