Asymptomatic norovirus infection during outbreaks in China: A systematic review and meta-analysis.

Acute gastroenteritis outbreaks may be caused by the excretion of norovirus (NoV) from asymptomatic individuals. Despite numerous studies involving asymptomatic NoV infection during outbreaks in China, a comprehensive assessment of its role has not been conducted, which is critical for emergency management. Our objective was to assess the prevalence of asymptomatic NoV infection during outbreaks in China. We conducted a comprehensive search of multiple databases, including PubMed, Web of Science, Cochrane Library, China National Knowledge Infrastructure, China Wanfang, and China Weipu, between January 1, 1997 and June 19, 2023. The retrieved articles and their references underwent screening, which utilized polymerase chain reaction-based assays for the detection of NoV in asymptomatic individuals during outbreaks that occurred in China. The primary summary data were the prevalence of asymptomatic NoV infection in outbreaks. We generated pooled estimates of asymptomatic prevalence in the population as a whole and in subgroups by using random-effect models. Of the 97 articles included, the pooled asymptomatic prevalence of NoV among 5117 individuals in outbreaks was 17.6% (95% confidence interval [CI]: 14.1-21.3). The asymptomatic prevalence of NoV GII (17.1%, 95% CI: 12.9-21.5) was similar to that of NoV GI (22.0%, 95% CI: 12.8-32.4). However, the proportion of asymptomatic individuals involved in NoV GII (57.44%) was significantly higher than that of NoV GI (5.12%), and NoV GII (75.26%) was reported much more frequently than NoV GI (14.43%) in the included articles. Meta-regression analysis of 11 possible influencing factors (geographic region, setting, season, sample type, genotype, transmission route, occupation, age, per capita income, study quality, and cases definition) showed that the source of heterogeneity might be related to the outbreak settings, per capita income, and study quality (p = 0.037, 0.058, and 0.026, respectively). Of particular note was the asymptomatic prevalence peaked in preschoolers (27.8%), afterward, it fell into trough in elementary and junior school children (10.5%), before the second peak located in adults (17.8%), and the elderly (25.2%). Prevalent genotypes reported include GII.4, followed by GII.17, GII.2, GII.3, GII.6, and so forth. The estimated asymptomatic prevalence of NoV during outbreaks in China was as high as 17.6%, with NoV GII dominating. In addition, genetic subtypes of NoV in outbreaks should be detected whenever possible. The role of asymptomatic individuals in NoV outbreaks cannot be ignored. This knowledge will help governments develop public health policies and emergency response strategies for outbreaks, assess the burden, and develop vaccines.

Epidemiology and transmission of hepatitis A in Shaanxi (western China) after more than ten years of universal vaccination.

Background: Hepatitis A (HepA) vaccination and economic factors can change the epidemiology of HepA. In China, the implementation of free vaccination for children under 1.5 years of age in 2008 has resulted in a decline in the overall incidence of HepA. Nevertheless, further investigation is required to comprehensively understand the epidemiological patterns of HepA in economically disadvantaged regions of China. Method: In this study, we evaluated the incidence, seroprevalence, and transmission characteristics of HepA in Shaanxi with less economically developed. We obtained data on reported cases of HepA from 2005 to 2020. Blood samples from 1,559 individuals aged 0 to 60 years were tested for anti-hepatitis A (HAV) antibodies. A questionnaire survey and blood sample collection were conducted in two sentinel sites from 2019 to 2021. Result: Between 2008 to 2020, the number of reported cases of HepA decreased from 3.44/100,000 person-years to 0.65/100,000 person-years, indicating an 81.1% decrease, which was particularly pronounced among younger age groups (0-19 years). From 2015-2020, infections were more likely to occur in people in their 40s and those over the age of 60. Farmers were still the most common occupation of HepA in the last decade. The results of the serological investigation showed the highest anti-HAV seroprevalence was observed in adults aged 39-60 years (94.6%) and those aged 28-38 years (87.8%). The 10-15 years group had the lowest seroprevalence at 49.3%. During the study period, a total of 22 cases were reported by sentinel sites, but the common risk factors (like raw food exposure, travel history, and closed contact with patients) were not identified. Conclusion: Given the greater severity of illness in the adult population and the ambiguous transmission routine, enhanced surveillance for HepA and evaluations that identify feasible approaches to mitigate the risk of HAV transmission are urgent priorities.

Safety analysis of a live attenuated mumps vaccine in healthy adolescents in China: A phase 4, observational, open-label trial.

Mumps is an acute infectious disease, which was well controlled in the past, but recently it has resurged in some areas. This study aimed to evaluate the safety profile of the live attenuated mumps vaccine after large-scale vaccination. We conducted an observational, open-label phase 4 trial in Shaanxi, China from October 2020 to March 2021. Eligible participants were freshmen of junior high school who were not above 14 years old. Adverse events following immunization (AEFI) monitoring was carried out by active and passive surveillance. Safety follow-ups were conducted during the study participation. Overall, 10057 subjects were enrolled in the active surveillance analysis. A total of 214 subjects reported adverse reactions with an incidence of 2.13% (214/10057). Most adverse reactions were grade 1, and the incidence of grade 1 adverse reactions was 1.44% (145/10057); 0.60% for grade 2 (60/10057); and 0.09% for grade 3 (9/10057). The majority of adverse reactions were solicited (1.73%, 174/10057). Injection-site pain was the most frequently reported local adverse reaction (0.71%, 71/10057), followed by redness (0.29%, 29/10057). The most common systemic adverse reactions were nausea (0.19%, 19/10057) and fever (0.16%, 16/10057). For passive AEFI surveillance, 57 AEFI cases were reported, with an incidence of 19.28/100000 (57/287608). And most AEFI cases were common adverse reactions (66.67%, 38/57). In total, the live attenuated mumps vaccine evaluated in this trial has a favorable safety profile and can be used for large-scale inoculation.

Impact of the COVID-19 pandemic on routine vaccination services in Shaanxi province, Northwest China: Non-pharmaceutical intervention period and mass COVID-19 vaccination period.

To better understand the impact of COVID-19 epidemic on routine vaccination, a cross-sectional study was carried out during non-pharmaceutical intervention period (2020) and mass COVID-19 vaccination period (2021) in Shaanxi province. Data on NIP (National Immunization Program, Free), nNIP (non-National Immunization Program, Paid), and COVID-19 vaccines inoculated and vaccination clinics were collected. At the beginning of the COVID-19 epidemic, the rate of routine vaccination clinics providing vaccination services was only 20.0%, rabies vaccination clinics was 89.9% and obstetric vaccination clinics was 95.9%. Compared with 2019 (as baseline), NIP vaccines inoculated in 2020 and 2021 decreased by 3.5% and 19.2%, respectively, on the contrary, nNIP vaccines increased by 25.8% and 34.7%, respectively. In 2021, 74.9% of vaccination clinics were involved in mass COVID-19 vaccination, and there was not a significant impact of mass COVID-19 vaccination on the number of other vaccines inoculated. Vaccination coverage of all NIP vaccines was not different from that in previous years. COVID-19 epidemic had a short-term impact on routine vaccination at beginning. The impact of mass COVID-19 vaccination on routine vaccination could even be ignored. The COVID-19 epidemic has once again made people realize the great harm of infectious diseases, and has improved everyone's willingness to receive routine vaccines.

Neutralizing antibody levels associated with injectable and aerosolized Ad5-nCoV boosters and BA.2 infection.

BACKGROUND: Several COVID-19 vaccines are in widespread use in China. Few data exist on comparative immunogenicity of different COVID-19 vaccines given as booster doses. We aimed to assess neutralizing antibody levels raised by injectable and inhaled aerosolized recombinant adenovirus type 5 (Ad5)-vectored COVID-19 vaccine as a heterologous booster after an inactivated COVID-19 vaccine two-dose primary series. METHODS: Using an open-label prospective cohort design, we recruited 136 individuals who had received inactivated vaccine primary series followed by either injectable or inhaled Ad5-vectored vaccine and measured neutralizing antibody titers against ancestral SARS-CoV-2 virus and Omicron BA.1 and BA.5 variants. We also measured neutralizing antibody levels in convalescent sera from 39 patients who recovered from Omicron BA.2 infection. RESULTS: Six months after primary series vaccination, neutralizing immunity against ancestral SARS-CoV-2 was low and neutralizing immunity against Omicron (B.1.1.529) was lower. Boosting with Ad5-vectored vaccines induced a high immune response against ancestral SARS-CoV-2. Neutralizing responses against Omicron BA.5 were ≥ 80% lower than against ancestral SARS-CoV-2 in sera from prime-boost subjects and in convalescent sera from survivors of Omicron BA.2 infection. Inhaled aerosolized Ad5-vectored vaccine was associated with greater neutralizing titers than injectable Ad5-vectored vaccine against ancestral and Omicron SARS-CoV-2 variants. CONCLUSIONS: These findings support the current strategy of heterologous boosting with injectable or inhaled Ad5-vectored SARS-CoV-2 vaccination of individuals primed with inactivated COVID-19 vaccine.

Immunogenicity, safety and consistency of seven lots of an inactivated COVID-19 vaccine in healthy children and adolescents: a randomized, double-blind, controlled, phase IV clinical trial.

Background: CoronaVac has been authorized worldwide for preventing coronavirus disease 2019. Information on the safety, immunogenicity and consistency of different lots and workshops of CoronaVac is presented here. Methods: In this randomized, double-blind, phase IV clinical trial in healthy children and adolescents aged 3-17 years, we aimed to assess the lot-to-lot and workshop-to-workshop consistency, as well as immunogenicity and safety of seven lots of commercial-scale CoronaVac from three workshops. Eligible participants were enrolled into three age cohorts (3-5, 6-11 and 12-17 years). Within each cohort, participants were randomly assigned to seven groups to receive two doses of CoronaVac, with four weeks apart. Serum samples were collected before the first dose and 28 days after the second dose for neutralizing antibody testing. The primary objective was to evaluate the consistency of immune response among different lots within workshop 2 or 3, as well as among different workshops. The primary endpoint was geometric mean titer (GMT) of neutralizing antibody at 28 days after full-course vaccination. Results: Between July 27th and November 19th, 2021, a total of 2,520 eligible participants were enrolled. Results showed that 95% confidence intervals (CIs) of GMT ratios for all comparative groups among different lots or workshops were within the equivalence criteria of [0.67, 1.5]. The GMT and seroconversion rate for all participants were 126.42 (95%CI: 121.82, 131.19) and 99.86% (95%CI: 99.59%, 99.97%) at 28 days after two-dose vaccination. The incidences of adverse reactions were similar among seven lots, and most adverse reactions were mild in Grade 1, with no serious adverse event. Conclusion: CoronaVac is well-tolerated and can elicit a good immune response among children and adolescents. Lot-to-lot consistency results indicate stable manufacturing of commercial-scale CoronaVac.

Seroepidemiology of Tetanus among Healthy People Aged 1-59 Years Old in Shaanxi Province, China.

The study aims to determine the seroprevalence of antibodies against tetanus among healthy people aged 1−59 years old in Shaanxi province. IgG against tetanus in serum samples were detected by ELISA. 6,439 subjects were enrolled. The positive rate (≥0.01 IU/mL) was 84.39% and GMC was 0.03 IU/mL. There were significant differences in positive rates (χ2 = 308.944, p < 0.01) and GMC (Z = 5,200,000, p < 0.01) among different age groups. The positive rates (χ2 = 304.3, p < 0.01) and GMCs (χ2 = 146.417, p < 0.01) showed regional differences. Both full protection rate (≥0.1 IU/mL) (χ2 = 36.834, p < 0.01) and GMC (Z = 688,000, p < 0.01) increased with the doses of tetanus-toxoid-containing vaccines (TTCVs) administered. The positive rate (χ2 = 54.136, p < 0.01) and GMC (Z = 140,200, p < 0.01) decreased gradually with the time interval after full immunization with TTCVs. The full protection rate (≥0.1 IU/mL) (χ2 = 176.201, p < 0.01) and GMC (Z = 629,900, p < 0.01) decreased with the interval (years) since the last dose of TTCVs. There were significant differences in the positive rates and GMCs for different ages, regions, immunization histories of TTCVs, and doses of TTCVs administered. The full protection rate and GMC decreased with the interval following full immunization with TTCVs and the interval since the last dose of TTCVs. The importance of using tetanus booster doses should be emphasized in adolescents and adults.

Seroepidemiology of pertussis and diphtheria among healthy adults in Shaanxi Province, northwest China: A large - scale cross-sectional study.

To determine the estimated pertussis incidence in adults and the need for a booster dose by detecting pertussis and diphtheria antibody levels in adults in Shaanxi province, China. Blood samples were collected from healthy individuals aged 18-59 years in Shaanxi province in 2017. Serum immunoglobulin G (IgG) antibodies against pertussis toxin (PT) and diphtheria toxin (DT) were determined using enzyme-linked immunosorbent assay. The data on reported pertussis cases in Shaanxi province were collected from the China Information System for Disease Control and Prevention and compared with the results of this study. A total of 4307 subjects were enrolled. The mean concentration of anti-PT IgG was 19.6 IU/mL (95% CI = 18.9-20.3), and the positive rate (≥40 IU/mL) was 11.0% (474/4307), of which recent infections (≥100 IU/mL) accounted for 1.2% (53/4307). Only one adult case of pertussis was reported in 2017, which is much lower than the results of this study. The mean concentration of anti-DT IgG was 0.04 IU/mL (95% CI = 0.04-0.05), and the positive rate (≥0.01 IU/mL) was 82.3% (3543/4307). The mean concentration of anti-DT IgG decreased from 0.07 IU/mL in the 18-29 year-old group to 0.03 IU/mL in the 50-59 year-old-group, and the positivity rate decreased from 86.7% to 78.7%. Our study suggests that pertussis is not uncommon among adults. The existing surveillance system might have underestimated the true incidence of pertussis. The diphtheria antibody levels decreased with age. Booster vaccination against pertussis should be considered for adolescents and young adults.

Immunogenicity and Safety of an Inactivated Enterovirus 71 Vaccine Administered Simultaneously with Hepatitis B Virus Vaccine, Group A Meningococcal Polysaccharide Vaccine, Measles-Rubella Combined Vaccine and Japanese Encephalitis Vaccine: A Multi-Center, Randomized, Controlled Clinical Trial in China.

BACKGROUND: The aim of this study was to investigate the immunogenicity and safety of the enterovirus 71 vaccine (EV71 vaccine) administered alone or simultaneously. METHODS: A multi-center, open-label, randomized controlled trial was performed involving 1080 healthy infants aged 6 months or 8 months from Shandong, Shanxi, Shaanxi, and Hunan provinces. These infants were divided into four simultaneous administration groups and EV71 vaccine separate administration group. Blood samples were collected from the infants before the first vaccination and after the completion of the vaccination. This trial was registered in the Clinical Trials Registry (NCT03519568). RESULTS: A total of 895 were included in the per-protocol analysis. The seroconversion rates of antibodies against EV71 in four simultaneous administration groups (98.44% (189/192), 94.57% (122/129), 99.47% (187/188) and 98.45% (190/193)) were non-inferior to EV71 vaccine separate administration group (97.93% [189/193]) respectively. Fever was the most common adverse event, the pairwise comparison tests showed no difference in the incidence rate of solicited, systemic or local adverse events. Three serious adverse events related to the vaccination were reported. CONCLUSIONS: The evidence of immunogenicity and safety supports that the EV71 vaccine administered simultaneously with vaccines need to be administered during the same period of time recommended in China.

Immunogenicity and safety of an inactivated enterovirus 71 vaccine co-administered with measles-mumps-rubella vaccine and live-attenuated Japanese encephalitis vaccine: a phase 4, single-center, randomized controlled trial.

Co-administration of vaccines could be an efficient strategy to increase vaccination uptake and reduce the number of clinic visits. This randomized controlled study aimed to evaluate the immunogenicity and safety of enterovirus 71 (EV71) vaccine co-administered with measles-mumps-rubella (MMR) vaccine and live-attenuated Japanese encephalitis vaccine (LA-JEV). A total of 372 healthy infants were randomly assigned in a 1:1:1 ratio to receive simultaneous administration of EV71 vaccine (dose 1) and MMR on d 0 and EV71 vaccine (dose 2) and LA-JEV on d 30 (Group 1); administration of MMR and LA-JEV on d 0 and 30, respectively (Group 2); or administration of doses 1 and 2 of EV71 vaccine on d 0 and 30, respectively (Group 3). The non-inferiority analysis of the seroconversion for EV71 neutralizing antibody after vaccination was the primary outcome. According to per protocol set, antibody response against EV71, measles, mumps, rubella, and Japanese encephalitis (JE) virus was similar regardless of administration schedule. After vaccination, the seroconversion rate of EV71 neutralizing antibody in Group 1 (107 [97.27%] of 110) was non-inferior to that in Group 3 (109 [97.32%] of 112; difference - 0.05% [95% CI - 5.38 to 5.21]). The incidences of adverse reactions were 62.60% (77/123) in Group 1, 54.84% (68/124) in Group 2, and 37.70% (46/122) in Group 3, and most of them were mild to moderate in severity. No vaccine-related serious adverse events were reported. In total, the co-administration of combined EV71 vaccine with MMR and LA-JEV showed no interference with antibody response and demonstrated good safety profiles.

Metagenomic sequencing reveals viral abundance and diversity in mosquitoes from the Shaanxi-Gansu-Ningxia region, China.

BACKGROUND: Mosquitoes host and transmit numerous arthropod-borne viruses (arboviruses) that cause disease in both humans and animals. Effective surveillance of virome profiles in mosquitoes is vital to the prevention and control of mosquito-borne diseases in northwestern China, where epidemics occur frequently. METHODS: Mosquitoes were collected in the Shaanxi-Gansu-Ningxia region (Shaanxi Province, Gansu Province, and Ningxia Hui Autonomous Region) of China from June to August 2019. Morphological methods were used for taxonomic identification of mosquito species. High-throughput sequencing and metagenomic analysis were used to characterize mosquito viromes. RESULTS: A total of 22,959 mosquitoes were collected, including Culex pipiens (45.7%), Culex tritaeniorhynchus (40.6%), Anopheles sinensis (8.4%), Aedes (5.2%), and Armigeres subalbatus (0.1%). In total, 3,014,183 (0.95% of clean reads) viral sequences were identified and assigned to 116 viral species (including pathogens such as Japanese encephalitis virus and Getah virus) in 31 viral families, including Flaviviridae, Togaviridae, Phasmaviridae, Phenuiviridae, and some unclassified viruses. Mosquitoes collected in July (86 species in 26 families) showed greater viral diversity than those from June and August. Culex pipiens (69 species in 25 families) and Culex tritaeniorhynchus (73 species in 24 families) carried more viral species than Anopheles sinensis (50 species in 19 families) or Aedes (38 species in 20 families) mosquitoes. CONCLUSION: Viral diversity and abundance were affected by mosquito species and collection time. The present study elucidates the virome compositions of various mosquito species in northwestern China, improving the understanding of virus transmission dynamics for comparison with those of disease outbreaks.

Epidemiological Characteristics, Seasonal Dynamic Patterns, and Associations with Meteorological Factors of Rubella in Shaanxi Province, China, 2005-2018.

Rubella occurs worldwide, causing approximately 100,000 cases annually of congenital rubella syndrome, leading to severe birth defects. Better targeting of public health interventions is needed to achieve rubella elimination goals. To that end, we measured the epidemiological characteristics and seasonal dynamic patterns of rubella and determined its association with meteorological factors in Shaanxi Province, China. Data on rubella cases in Shaanxi Province from 2005 to 2018 were obtained from the Chinese National Notifiable Disease Reporting System. The Morlet wavelet analysis was used to estimate temporal periodicity of rubella incidence. Mixed generalized additive models were used to measure associations between meteorological variables (temperature and relative humidity) and rubella incidence. A total of 17,185 rubella cases were reported in Shaanxi during the study period, for an annual incidence of 3.27 cases per 100,000 population. Interannual oscillations in rubella incidence of 0.8-1.4 years, 3.8-4.8 years, and 0.5 years were detected. Both temperature and relative humidity exhibited nonlinear associations with the incidence of rubella. The accumulative relative risk of transmission for the overall pooled estimates was maximized at a temperature of 0.23°C and relative humidity of 41.6%. This study found that seasonality and meteorological factors have impact on the transmission of rubella; public health interventions to eliminate rubella must consider periodic and seasonal fluctuations as well as meteorological factors.

How Socio-Environmental Factors Are Associated with Japanese Encephalitis in Shaanxi, China-A Bayesian Spatial Analysis.

Evidence indicated that socio-environmental factors were associated with occurrence of Japanese encephalitis (JE). This study explored the association of climate and socioeconomic factors with JE (2006-2014) in Shaanxi, China. JE data at the county level in Shaanxi were supplied by Shaanxi Center for Disease Control and Prevention. Population and socioeconomic data were obtained from the China Population Census in 2010 and statistical yearbooks. Meteorological data were acquired from the China Meteorological Administration. A Bayesian conditional autoregressive model was used to examine the association of meteorological and socioeconomic factors with JE. A total of 1197 JE cases were included in this study. Urbanization rate was inversely associated with JE incidence during the whole study period. Meteorological variables were significantly associated with JE incidence between 2012 and 2014. The excessive precipitation at lag of 1-2 months in the north of Shaanxi in June 2013 had an impact on the increase of local JE incidence. The spatial residual variations indicated that the whole study area had more stable risk (0.80-1.19 across all the counties) between 2012 and 2014 than earlier years. Public health interventions need to be implemented to reduce JE incidence, especially in rural areas and after extreme weather.

Identify the susceptibility profile to measles in the general population: Serological survey of measles antibodies in Shaanxi province, China, in 2016.

The reported coverage with two doses of the measles vaccine (MCV) in Shaanxi Province, China, is greater than 95%, but the measles incidence over the whole province remains high. Cross-sectional serological surveys of measles antibodies in Shaanxi Province were conducted in 2016 to assess the population's immunity. The measles IgG levels were measured in serum samples using ELISA. The geometric means concentration (GMC) levels and seroprevalence rates with 95% CIs were calculated by region, gender, and age. A total of 3574 serum samples were collected from participants aged from 2 months to 49 years. The GMC of measles antibodies was 471.3 mIU/ml (95% CI: 445.9-498.2 mIU/ml), and the seroprevalence was only 85.9% (95% CI: 84.8-87.1%). A significant difference in the GMC (P < .05) but not the seroprevalence (P > .05) was observed among the 3 regions. The report measles incidences were high in individuals aged 0-7 months (33.2/100 000) and 8-17 months (26.8/100 000). Although both measles immunity (90.7%) and MCV coverage (89.7%) were low in children aged 8-17 months, the measles seroprevalence in adults was high at greater than 90%. These results revealed that further actions may be taken to increase vaccination coverage in children aged 8 months to 5 years over the whole province and teenagers in the south region. In particular, timely administration of the first MCV dose should be emphasized to prevent measles epidemics in children aged 8-17 months. Vaccination strategies may be varied by age and region.

Distribution and phylogenetic analysis of Culex flavivirus in mosquitoes in China.

Culex flavivirus (CxFV) is an insect-specific virus of the genus Flavivirus. CxFV strains have been isolated from Cx. pipiens, Cx. quinquefasciatus, and other Cx. species in Asia, Africa, North America, Central America and South America. CxFV was isolated for the first time in China in 2006. As this is a novel flavivirus, we explored the distribution and genetic characteristics of Culex flavivirus in China. A total of 46,649 mosquitoes were collected in seven provinces between 2004 and 2012 and were analysed in 871 pools. 29 CxFV RNAs from Cx. pipiens, Cx. tritaeniorhynchus, Anopheles Sinensis, and Culex spp. tested positive for CxFV in real-time RT-PCR. 6 CxFV strains were isolated from Cx. species collected in Shandong, Henan, and Shaanxi provinces, while no virus or viral RNA was detected in samples from Sichuan, Chongqing, Hubei, and Fujian. Phylogenetic analysis of the envelope gene indicated that Chinese strains formed a robust subgroup of genotype 1, together with viruses from the United States and Japan. This study demonstrates that the geographic distribution of CxFV in China is widespread, but geographical boundaries to spread are apparent. Our findings suggest that CxFV can infect various mosquito species in nature.

An improved FCM medical image segmentation algorithm based on MMTD.

Image segmentation plays an important role in medical image processing. Fuzzy c-means (FCM) is one of the popular clustering algorithms for medical image segmentation. But FCM is highly vulnerable to noise due to not considering the spatial information in image segmentation. This paper introduces medium mathematics system which is employed to process fuzzy information for image segmentation. It establishes the medium similarity measure based on the measure of medium truth degree (MMTD) and uses the correlation of the pixel and its neighbors to define the medium membership function. An improved FCM medical image segmentation algorithm based on MMTD which takes some spatial features into account is proposed in this paper. The experimental results show that the proposed algorithm is more antinoise than the standard FCM, with more certainty and less fuzziness. This will lead to its practicable and effective applications in medical image segmentation.

[Analysis on neutralization antibody titer of Japanese B encephalitis virus in healthy population in Shaanxi province].

OBJECTIVE: To detect Japanese B Encephalitis virus (JEV) neutralization antibody (NA) titer and evaluate immunologic barrier, analyze the factor of affecting JEV NA titer, and provide the data for JE control. METHOD: Cluster sampling was selected randomly in the region of high, middle, low JE incidence rate. To detect the NA of JEV by micro neutralization test. RESULTS: The positive rate of JEV NA (and GMT) was 81.3% (1:27.84) in Ankang prefecture where JE incidence rate was high, 47.9% (1:7.41) in Baoji prefecture where JE incidence rate was middle, 24.1% (1:3.04) in Tongchuan prefecture where JE disease rate was low. There was the tendency that JEV NA titer increased with increasing age in the region of high JE disease rate, and there was not this tendency in the region of low JE incidence rate. CONCLUSION: In shaanxi province, the children's JEV NA titer was low in the region of high JE incidence rate, and it is important to vaccinate JE vaccine for children. The adult's JEV NA titer was low in the region of low JE incidence rate. And it is important to control JE disease in adult groups.

[Analysis on data from the clinical acute viral encephalitis surveillance system in three prefectures in Shaanxi during 2005 - 2006].

OBJECTIVE: To describe the epidemiological features of viral encephalitis and burden of Japanese encephalitis (JE), and to identify potential strategies for effective JE control measures, using data from the Viral Encephalitis Surveillance Program (VESP) launched in Ankang, Baoji, and Weinan prefectures, Shaanxi province. METHODS: Data was gathered from sentinel hospitals reporting system on all the viral encephalitis (VE) cases identified between June 2005 and May 2007. County Center for Disease Control and Prevention (CDC) investigated the cases, drawing blood and cerebrospinal fluid (CSF) samples from the hospitals, and testing IgM antibody against JE using ELISA. We used Epi Data and Excel for data entry and analysis. RESULTS: A total of 1097 VEs were reported and 1053 (96.0%) had blood or CSF samples collected and tested for IgM antibody against JE. Three hundred and eleven cases (29.5%) showed JE antibody positive (JE confirmed case). Among the JE confirmed cases, numbers of those under 15 year of age accounted for 33.7%, 43.9% and 88.3% in Baoji, Weinan and Ankang prefectures respectively. The rest were mainly children aged 5-14 years old (53.3%). Toddlers,farmers and children accounted for 85.2% in JE confirmed cases. About half of other VE cases (51.0%) were students of all age. Data an investigation on 398 reported VE cases at discharge, showed that 67.1% of JE confirmed cases recovered while 83.7% of the other VE cases fully recovered. The case fatality rates were 9.2% for JE confirmed cases and 3.1% for other VE cases. 578 cases were followed up at 90-days after discharge, 69.6% of JE confirmed cases and 90.2% of other VE cases recovered, with case fatality rates were 13.6% and 3.6% for JE confirmed cases and for other VE cases, respectively. The sequelae rates were 10.0% for JE confirmed cases and 4.5% for other VE cases. CONCLUSION: The peak of the VE season was the same as that of JE. There were 45.6% of reported JE cases with negative JE IgM, suggesting that it is necessary to carry out laboratory testing for clinical diagnosis cases. The fact that high risk population was different at prefectures levels suggested that more attention be paid in JE control and prevention.