Prevention and control strategy of COVID-19 in the vaccine era / 预防医学

Abstract@#Globally, non-pharmacological interventions, such as keeping social distance and wearing masks, are the primary prevention and control strategy in the early stage of the coronavirus disease 2019 (COVID-19) pandemic. The successful development and the urgency use of the COVID-19 vaccines in some countries brings a new stage of combining immunization with non-pharmacological interventions in the fight with COVID-19. For the shortage of vaccines, the immunization strategies vary in countries. To end the pandemic, 47%-85% of the population should be immunized with effective COVID-19 vaccines, thus we should boost the yield of vaccines, formulate scientific immunization strategies, promote the mass immunization, improve the willingness of vaccination, and increase the equity of vaccine allocation; meanwhile, we should strengthen the surveillance of virus variation, vaccine effectiveness and safety, and keep on the vaccine research to copy with the potential threat of the virus variation.

Epidemiological features and viral shedding in children with SARS-CoV-2 infection.

A pandemic of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection broke out all over the world; however, epidemiological data and viral shedding in pediatric patients are limited. We conducted a retrospective, multicenter study, and followed-up with all children from the families with SARS-CoV-2 infected members in Zhejiang Province, China. All infections were confirmed by testing the SARS-CoV-2 RNA with real-time reverse transcription PCR method, and epidemiological data between children and adults in the same families were compared. Effect of antiviral therapy was evaluated observationally and fecal-viral excretion times among groups with different antiviral regiments were compared with Kaplan-Meier plot. By 29 February 2020, 1298 cases from 883 families were confirmed with SARS-CoV-2 infection and 314 of which were families with children. Incidence of infection in child close contacts was significantly lower than that in adult contacts (13.2% vs 21.2%). The mean age of 43 pediatric cases was 8.2 years and mean incubation period was 9.1 days. Forty (93.0%) were family clustering. Thirty-three children had coronavirus disease 2019 (20 pneumonia) with mild symptoms and 10 were asymptomatic. Fecal SARS-CoV-2 RNA detection was positive in 91.4% (32/35) cases and some children had viral excretion time over 70 days. Viral clearance time was not different among the groups treated with different antiviral regiments. No subsequent infection was observed in family contacts of fecal-viral-excreting children. Children have lower susceptibility of SARS-CoV-2 infection, longer incubation, and fecal-viral excretion time. Positive results of fecal SARS-CoV-2 RNA detection were not used as indication for hospitalization or quarantine.

Risk factors for avian influenza virus in backyard poultry flocks and environments in Zhejiang Province, China: a cross-sectional study.

BACKGROUND: Human infection of avian influenza virus (AIV) remains a great concern. Although live poultry markets are believed to be associated with human infections, ever more infections have been reported in rural areas with backyard poultry, especially in the fifth epidemic of H7N9. However, limited information is available on backyard poultry infection and surrounding environmental contamination. METHODS: Two surveillance systems and a field survey were used to collect data and samples in Zhejiang Province. In total, 4538 samples were collected by surveillance systems and 3171 from the field survey between May 2015 and May 2017, while 352 backyard poultry owners were interviewed in May 2017 by questionnaire to investigate factors influencing the prevalence of avian influenza A virus and other AIV subtypes. RT-PCR was used to test the nucleic acids of viruses. ArcGIS 10.1 software was used to generate maps. Univariate and logistic regression analyses were conducted to identify risk factors for AIV infection. RESULTS: Of the 428 poultry premises observed by the surveillance system, 53 (12.38%) were positive for influenza A virus. Of the 352 samples from poultry premises observed by field survey, 13 (3.39%) were positive for influenza A virus. The prevalence of AIV was unevenly distributed and the dominant subtype differed among cities. Eastern (Shaoxing and Ningbo) and southern (Wenzhou) cities exhibited a higher prevalence of AIV (16.33, 8.94, and 7.30% respectively). Contamination of AIV subtypes was most severe in January, especially in 2016 (23.26%, 70/301). The positive rate of subtype H5/H7/H9 was 2.53% (115/4538). Subtype H5 was the least prevalent, while subtypes H7 and H9 had similar positivity rates (1.50 and 1.32% respectively). Poultry flocks and environmental samples had a similar prevalence of AIV (4.46% vs 5.06%). The type of live birds was a risk factor and the sanitary condition of the setting was a protective factor against influenza A contamination. CONCLUSIONS: AIV subtypes were prevalent in backyard poultry flocks and surrounding environments in Zhejiang Province. The types of live birds and sanitary conditions of the environment were associated with influenza A contamination. These findings shine a light on the characteristics of contamination of AIV subtypes and emphasize the importance of reducing AIV circulation in backyard poultry settings.

Nosocomial transmission of avian influenza A (H7N9) virus in China: epidemiological investigation.

STUDY QUESTION: Can avian influenza A (H7N9) virus be transmitted between unrelated individuals in a hospital setting? METHODS: An epidemiological investigation looked at two patients who shared a hospital ward in February 2015, in Quzhou, Zhejiang Province, China. Samples from the patients, close contacts, and local environments were examined by real time reverse transcriptase (rRT) polymerase chain reaction (PCR) and viral culture. Haemagglutination inhibition and microneutralisation assays were used to detect specific antibodies to the viruses. Primary outcomes were clinical data, infection source tracing, phylogenetic tree analysis, and serological results. STUDY ANSWER AND LIMITATIONS: A 49 year old man (index patient) became ill seven days after visiting a live poultry market. A 57 year old man (second patient), with a history of chronic obstructive pulmonary disease, developed influenza-like symptoms after sharing the same hospital ward as the index patient for five days. The second patient had not visited any poultry markets nor had any contact with poultry or birds within 15 days before the onset of illness. H7N9 virus was identified in the two patients, who both later died. Genome sequences of the virus isolated from both patients were nearly identical, and genetically similar to the virus isolated from the live poultry market. No specific antibodies were detected among 38 close contacts. Transmission between the patients remains unclear, owing to the lack of samples collected from their shared hospital ward. Although several environmental swabs were positive for H7N9 by rRT-PCR, no virus was cultured. Owing to delayed diagnosis and frequent hospital transfers, no serum samples were collected from the patients, and antibodies to H7N9 viruses could not be tested. WHAT THIS STUDY ADDS: Nosocomial H7N9 transmission might be possible between two unrelated individuals. Surveillance on patients with influenza-like illness in hospitals as well as chickens in live poultry markets should be enhanced to monitor transmissibility and pathogenicity of the virus. FUNDING, COMPETING INTERESTS, DATA SHARING: Funding support from the Program of International Science and Technology Cooperation of China (2013DFA30800), Basic Work on Special Program for Science and Technology Research (2013FY114600), National Natural Science Foundation of China (81402730), Special Program for Prevention and Control of Infectious Diseases in China (2013ZX10004218), US National Institutes of Health (1R01-AI108993), Zhejiang Province Major Science and Technology Program (2014C03039), and Quzhou Science and Technology Program (20111084). The authors declare no other interests and have no additional data.

Human infection and environmental contamination with Avian Influenza A (H7N9) Virus in Zhejiang Province, China: risk trend across the three waves of infection.

BACKGROUND: The third wave of H7N9 cases in China emerged in the second half of 2014. This study was conducted to identify the risk trends of H7N9 virus in human infections and environment contamination. METHODS: A surveillance program for H7N9 virus has been conducted in all 90 counties in Zhejiang since March 2013. All H7N9 cases were reported by hospitals through the China Information System for Disease Control and Prevention. Sampling sites for environment specimens were randomly selected by a multi-stage sampling strategy. Poultry-related workers for serological surveillance were randomly selected from the sampling sites for environmental specimens in the first quarter of each year. rRT-PCR and viral isolation were performed to identify H7N9 virus. A hemagglutination inhibition assay was conducted to detect possible H7N9 infection among poultry-related workers. RESULTS: A total of 170 H7N9 cases were identified in Zhejiang from 20 March 2013 to 28 February 2015. The proportion of rural cases increased from 42.2% (19/45) to 67.7% (21/31) with progression of the three epidemics (P < 0.05). In 32% (161/503) of towns and 16.0% (238/1488) of surveyed premises, H7N9 virus was detected in the environment. The positive rate of environmental specimens was 6.1% (868/14207). In addition, 912 poultry-related workers were recruited and 3.7% (34) of them tested positive for H7N9 antibodies. Positive detection of H7N9 virus during environmental surveillance increased from the first to third wave (P < 0.05). Almost all positive rates of environmental surveillance were higher in urban than rural in the second wave (P < 0.05), however they were higher in rural area in the third wave (P < 0.05). CONCLUSIONS: Our study highlights that the severity of poultry-related environmental contamination by H7N9 virus is intensifying. We strongly recommend that the local government stop illegal trading immediately and close live poultry markets in the territory. Poultry operations in slaughtering plants must be supervised rigorously. Prior to the closure of live poultry markets, daily cleaning and disinfecting of areas potentially contaminated by H7N9 virus, centralized collection and disposal of trash, designating certain days as market rest days, banning overnight poultry storage and other measures should be strictly carried out in both urban and rural areas.

[Analysis on coverage rate of primary immunization of measles vaccine among migrant children in Yiwu, Zhejiang province from 2007 to 2010].

OBJECTIVE: To investigate the coverage rate of primary immunization of measles containing vaccine (MCV1) among migrant children in Yiwu,Zhejiang province. METHODS: Household cluster sampling survey and probability proportion to size sampling method were adopted. A total of 967 migrant children born from 1st July 2007 to 1st July 2010 and their caregivers were selected as target population. Standard face-to-face interviews were conducted to investigate the subjects' knowledge, attitude, practice (KAP) of immunization, MCV1 vaccination and determinants. Multi-variable weighted average score method was adopted to evaluate the result of our survey on KAP. Kaplan-Meier analysis was adopted to assess the coverage of MCV1 and Cox regression analysis was adopted to explore the influencing factors associated with the coverage of MCV1. RESULTS: Out of the 967 children, 104 were born in 2007, accounting for 10.8%; 301 were born in 2008, accounting for 31.1%; 343 were born in 2009, accounting for 35.5% and 219 were born in 2010, accounting for 22.6%. Among the surveyed caregivers, 71.9% (695/967) were mothers and 90.2% (872/976) were migrant from other provinces. According to the result of survey on KAP among caregivers, 56.2% (543/967) scored ≥ 4 points on knowledge, 75.8% (734/967) scored ≥ 4 points on attitude and 48.7% (471/967) scored ≥ 4 points on behavior. 86.6% (838/967) of surveyed caregivers' education levels were under junior middle school.85.9% (831/967) of the migrant children were born in hospitals.36.3% (351/967) of the surveyed families' household income were under 2000 yuan per month.32.7% (316/967) of surveyed caregivers waited less than 15 min for immunization for each time. Coverage rate of MCV1 was 85.9% (831/967; 95%CI: 83.7%-88.1%). The timely coverage rates at 8 months, 12 months, and 24 months were 58.8% (569/967; 95%CI: 55.5%-62.1%), 88.2% (853/967; 95%CI: 86.0%-90.4%) and 98.6% (953/967; 95%CI: 97.8%-99.4%), respectively. The average age of MCV1 immunization for each birth cohort between 2007 and 2010 were 10.4, 10.1, 10.1 and 9.3 month, respectively; without statistical significance (χ(2) = 0.722, P = 0.398). According to the analysis by Cox regression, the caregivers aged ≤ 25 years (24.3% (235/967), RR = 1.520 (95%CI: 1.280-1.800)), the caregivers' education level above college (2.8% (27/967), RR = 3.841 (95%CI: 2.287-6.451)), delivered in county-level hospital (49.4% (478/967), RR = 6.048 (95%CI: 4.311-8.485)), household income > 4000 yuan per month (21.7% (210/967), RR = 1.366 (95%CI:1.163-1.604)), the average score of attitude towards immunization ≥ 4 points (75.9%(734/967), RR = 2.613 (95%CI: 1.026-6.655)), the average waiting time for each vaccination ≤ 15 min (32.7% (316/967), RR = 2.116 (95%CI: 1.341-3.339)) were the important factors to improve the timely immunization coverage rate of MCV1 among migrant children. CONCLUSION: The coverage of MCV1 were obviously delayed among migrant children in Yiwu, Zhejiang province. We suggest that the investigation of migrant children should be strengthened and remind or recall mechanism for immunization should be established. Increasing the open days for immunization clinics and reducing the waiting time for vaccination could also improve the coverage and timeliness of the MCV vaccination.

[Clinical and epidemiological characteristics of the 6 confirmed human cases with novel influenza A (H7N9) virus infection in Zhejiang].

OBJECTIVE: To explore the clinical spectrum, geographic location of human H7N9 avian influenza as well as the characteristics of population at high risk of infection, in order to develop strategies for the prevention and control of the infection. Clinical and epidemiological characteristics on the 6 confirmed human cases in Zhejiang were also analyzed. METHODS: Real-time fluorescent quantitative PCR was used to test the nucleic acid of human H7N9 avian influenza infection, from pharyngeal swabs of the patients and their close contacts. Face to face interview and descriptive method were used to collect related clinical and epidemiological data. Statistical analysis was performed by SPSS 17.0. RESULTS: Six confirmed cases were distributed in Hangzhou and Huzhou cities. The 6 confirmed human cases, including 5 males and 1 female were all confirmed with novel influenza A (H7N9) virus infection, with an average age as 60.83 years (with median as 64.50 years). Cough was the most common initial symptom to be noticed. The clinical manifestations would include fever, dizziness, pain of muscles, coughing, expectoration and short of breath. All the X-ray chest films showed severe pneumonia, and 5 of them having had other chronic diseases. None of the cases admitted to have had a history of exposure to ill/death avians. However, all of the cases had been frequently exposed to the agricultural-byproduct-trading-markets where the positive rate of novel influenza A (H7N9) virus in environmental specimens was up to 43.21%. 32 of the 375 close contacts (8.53%) to the 6 cases appeared abnormal symptoms, but no positive result related to novel influenza A (H7N9) virus nucleic acid was detected from their throat swabs. CONCLUSION: Acute infection on the respiratory system seemed the main clinical manifestation. Elderly men, especially those with chronic diseases were under high risk of human infection with H7N9 avian influenza. The source of infection might be associated with the exposure to poultry. There was still lack of evidence to confirm the route of person to person transmission on H7N9 avian influenza.

Evidence for H5 avian influenza infection in Zhejiang province, China, 2010-2012: a cross-sectional study.

BACKGROUND: The first outbreak of H5N1 highly-pathogenic avian influenza (HPAI) virus associated with several human deaths occurred in 1997 in Hong-Kong, China. While H5N1 virus infection in poultry workers has been studied in some detail, little is known about the environmental risk factors of the H5 avian influenza virus infection in China. METHODS: A cross-sectional study was performed to evaluate the environmental load of H5 viruses in poultry-contaminated environments and to explore potential risk factors associated with infection in poultry workers between October 2010 and March 2012. Serum and environmental samples were collected in Zhejiang province, China. The hemagglutination inhibition (HI) assay was used to analyze human sera for antibodies against H5N1 virus [A/Hubei/1/2010 (H5N1) and A/Anhui/1/2005 (H5N1)]. All participants were interviewed with a standardized questionnaire to collect information on exposure to poultry. H5 Avian influenza virus in the environmental samples was detected by real time RT-PCR. RESULTS: One hundred and five of 3,453 environmental samples (3.0%) tested positive for H5 avian influenza virus. Fifty-five of 1,169 subjects (4.7%) tested seropositive for anti-H5N1 antibodies. A statistically significant difference in H5 virus detection rate was found among the different environments sampled (<0.001), with the highest showed in live bird markets (68.6%). Detection rate varied according to the source of samples, sewage (9.5%), drinking water (19.0%), feces (19.0%), cage surface (25.7%), and slaughtering chopping boards (15.2%), respectively. Direct or close contact with poultry (OR =5.20, 95% CI, 1.53-17.74) and breeding numerous poultry (OR =3.77, 95% CI, 1.72-8.73) were significantly associated with seroprevalence of antibodies to avian influenza virus A (H5N1). CONCLUSIONS: The number of birds bred more than 1,000 and direct or close contact with poultry in the workplace or the environment would be a potential risk of H5N1 infection.

Waning immunity to measles in young adults and booster effects of revaccination in secondary school students.

The increasing proportions of adult cases were observed in the recent measles outbreaks in Zhejiang Province, China. In order to identify the high-risk age groups of measles for targeted intervention, a seroprevalence survey of measles antibody was conducted among 1961 participants aged 0-60 years randomly selected by age-stratified purpose sampling, and the effect of revaccination program in secondary school was evaluated in Zhejiang Province. The adjusted overall seropositivity rate of measles was 88% (95% confidence interval [CI]: 86-89%) with geometric mean titers (GMT), 976±86 mIU/ml. The seropositivity rate of measles was significantly lower in subjects aged 15-19 years than aged 5-9 years (90% vs 96%, χ(2)=5.21, p=0.022). Both seropositivity rate and GMT level of measles were higher in participants aged 10-14 years with ≥2 doses MCV than those with only 1 dose (95% vs 81%, 1276 mIU/ml vs 666 mIU/ml). The seropositivity rate increased from 91% to 100% after revaccination with MCV among 184 secondary school students. The proportions of measles cases aged ≥15 years were reduced gradually (χ(2)=55.47, p=0.000) from 2009 to 2011 after implementing the revaccination campaign on secondary school students since 2008. Our findings strongly suggested that a revaccination opportunity with MCV for adolescents helps to improve the population immunity, and it can be conducted effectively and practically in secondary school students.

[Epidemiological effects of the A (H1N1) influenza vaccine immunization program on students].

OBJECTIVE: To evaluate the epidemiological effects of vaccine immunization program related to A (H1N1) influenza in the middle school students. METHODS: Non-randomized clinical trial was designed to assess the A (H1N1) influenza vaccine on its efficacy. 14 883 students from 8 middle schools in Zhejiang province were recruited and classified into vaccinated or control groups, based on the status of immunization with A (H1N1) influenza vaccine. All subjects were followed up through one epidemic period (6 months) and the incidence rates of influenza-like illnesses, A (H1N1) influenza, and seasonal influenza in these two groups were compared to evaluate the efficacy of the vaccine. RESULTS: There were 6334 subjects in the vaccinated group and 8549 in the control group. 7441.75 person-years were followed from these two groups. The incidence rate of A (H1N1) influenza in vaccinated group was 1.64‰ per person-year, lower than that of the control group. The rate difference (RD) was -1.64‰ per person-year (95% confidence interval value from -3.04‰ to -0.23‰ per person-year), and the difference was significant (P = 0.010). The incidence rate of influenza-like illnesses in vaccinated group was 21.47‰ per person-year, lower than that of the control group (22.69‰ per person-year) and the difference was not significant (P > 0.05). The incidence rate of B influenza in vaccinated group was 6.63‰ per person-year, higher than that of control group (7.02‰ per person-year) but the difference was not significant (P > 0.05). CONCLUSION: This vaccine demonstrated a good epidemiological effect against the A (H1N1) influenza virus infection, observed through a student-immunization program. The cross-protection effect against the influenza-like illnesses and other seasonal influenzas was not noticed in this study.

[An outbreak of measles among unvaccinated migrant population in Zhejiang province, from June to August, 2010].

OBJECTIVE: On July 6, 2010, the parents of a patient with confirmed measles reported several suspected measles patients with fever and rash in their village. An investigation was carried out to verify and understand the cause of the outbreak. METHODS: Several suspected cases had an onset of fever and rash in this and other neighboring villages during June 1 to August 3, 2010. A confirmed case was a suspected case with measles-specific IgM identified in the serum. We conducted door-to-door visits and searched the Chinese Center for Disease Control and Prevention Information System to identify cases, also conducted a retrospective cohort study among migrant children aged 8 months-14 years to identify risk factors related to measles. RESULTS: We identified 19 measles cases (17 confirmed case, 2 suspected cases) in the village, and all of them were migrants. Children aged 1-2 years had the highest attack rate (13%). The primary case-patient had onset on the day she arrived in this village (June 4, 2010). Caretakers from an unlicensed private clinic were providing service in the village but did not report the outbreak to the public health authority. The outbreak was identified only after receiving a report from the parents of one of the patients, by that time the outbreak had lasted for one month. The measles vaccine coverage rate was 81% among the 315 migrant children aged 8 months-14 years. Among the 61 unvaccinated children, those who reportedly being contacted a measles patient had a higher attack rate (14/16, 88%) than those who did not (2/45, 4.4%) (Relative risk = 20, Fisher's exact 95% confidence interval: 5.7-94). CONCLUSION: The low measles vaccine coverage among migrant children and lack of measures taken on the incident, timely isolation diagnosis/reporting by the caretakers from the unlicensed private clinic etc. had contributed to this prolonged outbreak. Measures need to be taken to improve the immunization services for migrant populations and to enhance measles surveillance programs in the area.

[Case-control study on epidemiology factors of measles in Zhejiang Province in 2008].

OBJECTIVE: In order to analysis the main factors of measles prevalence in 2008, and to provide evidence for establishing scientific strategies on measles elimination. METHODS: 1:1 matched case-control study was conducted in 3 cities, and the conditional logistic regression was used to analyse the risk factor of measles. RESULTS: 358 matched pairs (716 objects) were investigated. Floating population, hospital exposure were related factors by single factor conditional logistic regression, and multiple factor conditional logistic regression showed the odds ratio of hospital exposure was 2.33 (P < 0.05). Meanwhile, non-immunization was the main possible risk factor in the subjects aged from 8 months to 2 years, which odds ratios for measles was 65.29 (P < 0.05). CONCLUSION: Hospital exposure, floating population and existing of non-immunization were the main factor for measles prevalence. It is necesarry to strengthen supervision and education for reducing the exposure opportunities. To perfect the floating population management and ensure the high coverage of 2 dose measles vaccine in children are suggested.

[A safety assessment on adverse reaction of recombinant B-subunit/inactivated whole cell oral cholera vaccine among non-infected population].

OBJECTIVE: To observe the safety of recombinant B-subunit/inactivated whole cell (rBS/WC) oral cholera vaccine among non-infected population. METHOD: A method of double-blind and case control was conducted randomly. 3041 non-infected persons who aged from 5- to 60-years-old were divided randomly into 3 groups, including 2 vaccine groups and 1 placebo group. The vaccine and placebo were taken respectively by vaccine groups and placebo group on the 1st, 7th and 28th day in every months of sequential 3 months. The adverse reaction was observed in sequential 3 days after intaking orally. The follow-up interviews were conducted in 1, 2, 3 months. RESULTS: No severe adverse reaction was occurred. The rate of adverse reaction was 1.70% in vaccine groups, 1.74% in placebo group. There was no statistically significant difference between two groups (chi2=0.013, P=0.909). The adverse reaction were mainly abdominal pain, diarrhea, partly anaphylaxis, and the others of dizziness, fatigue, weakness. Most people recovered within short time without any medical treatment. The adverse reactions might be related to psychogenic reaction. CONCLUSION: The safety of oral rBS/WC cholera vaccine among non-infected population was pretty good.

[Safety and immunogenicity of lyophilized live attenuated domestic varicella vaccine].

OBJECTIVE: To evaluate the safety and immunogenicity of the lyophilized live attenuated domestic varicella vaccine of Oka strain in Zhejiang province. METHODS: 785 susceptible children aged 1-13 years, who had no history of VZV infection and had not been immunized, were observed. RESULTS The results showed that 2.29% children had adverse reactions after 30 mins of inoculation, 3.69% children had adverse reactions after 4 hours, 3.82% children had adverse reactions after 24 hours, 1.78% children had adverse reactions after 48 hours, 0.25% children had adverse reactions after 72 hours, no adverse reactions were observed after six weeks. There were 3.82% children had fever, The incidence rate of other adverse reactions such as swell and scleroma were low. The vaccine had high sero-converson rate. CONCLUSION: The results showed that it has good safety and immunogenicity of the live attenuated domestic varicella vaccine.

[Study on relationship between hepatitis B virus DNA load and genotype with large envelope protein].

OBJECTIVE: To explore the relation between hepatitis B virus DNA load and genotype with the level of large envelope protein. METHODS: Serum HBV DNA was quantitively detected by using real time polymerase chain reaction (RT-PCR). The LHBs were detected by using enzyme linked immuno sorbent assay (ELISA) and HBV markers were detected by time differentiate immunofluorescence assay in 140 serum samples collected from chronic hepatitis B patients.The genotypes of HBV were identified by DNA sequencing; and analyze their relationship. RESULTS: There was no significant difference between positive rate of LHBs and that of HBV DNA in HBeAg negative and positive group (P > 0.05); The HBV LHBs absorbency was markedly correlated with the HBV DNA load ( R2 = 0.9267). The difference of HBV LHBs absorbency between HBV genotype B and C was not significant. CONCLUSIONS: The close correlation between HBV LHBs absorbence and HBV DNA load illustrated that he level of serum LHBs can be used to estimate the state of HBV replication; and there is no relationship between HBV LHBs absorbency and genotypes. So HBV LHBs may be used as a new serological marker to detect HBV replication.

[The emergence of candidate pathogenicity island 89K DNA sequence of Streptococcus suis isolated from sporadic patients in Zhejiang province].

OBJECTIVE: To identify the presence of candidate pathogenicity island 89K DNA sequence of Streptococcus suis serotype 2 (SS2) strains isolated from patient in Zhejiang province. METHODS: Genes and DNA fragments were amplified by PCR, using specific primers, and three amplified fragments of the 89K sequence were directly sequenced. The results were analyzed using software related to bioinformatics and epidemiology. RESULTS: 8 strains of SS2 all contained 89K sequence, cps2J and mrp virulent genes, and species-specific 16S rDNA. 3 amplified fragments of 89K candidate pathogenicity island of SS2 ZJ0501 were above 99% similar to SS2 strain identified from outbreaks in Jiangsu in 1998, and the gene fragment of coding DNA recombinant protein in the 89K sequence was highly homological with that of S. dysgalactiae and S.agalactiae. CONCLUSION: In recent years SS2 strains isolated from patients with clinical symptoms in Zhejiang province had been detected to have contained candidate pathogenic 89K DNA fragment.

[Study on a 10-year protective effects of vaccination against hemorrhagic fever with renal syndrome].

OBJECTIVE: To evaluate the epidemiological and serological efficacy after 10 years of vaccination against hemorrhagic fever with renal syndrome (HFRS) vaccines in Zhejiang province. METHODS: One county was randomly chosen as the research unit with all the healthy people between 16 and 60 years old were equally divided into study and control groups. The study group was vaccinated. Immunofluorescent antibody assay was used to test specific IgG antibody and Mcro-CPE method was used to test the titer of neutralizing antibody. RESULTS: Two weeks after the full-course immunization, the seroconversion rate became 100% (67/67, with 95% CI as 96.3%-100%) by immunofluorescent antibody test (IgG) and 44.4% (8/18 with 95% CI as 22.0%-69.0%) by neutralization test with GMT titers as 72.1 and 4.6 respectively. Booster immunization was provided one year later. Time span as two weeks prior to, one year, one and half years, two years, three years and five years after booster immunization, the rates of seroconversion on immunofluorescent antibody using IFAT method, were 28.6%, 83.3%, 75.0%, 53.1%, 22.6%, 10.0% and 55.0% respectively, and rates of seroconversion of neutralizing antibody by Mcro-CPE method were 14.8%, 55.6%, 35.0%, 31.3%, 26.0%, 10.0% and 50.0% respectively. Nine years after the reinforcement, the rates of seroconversion of immunofluorescent antibody by IFAT method was only 7.1%. The vaccinated group had no patient seen but the control group appeared 34 patients including 3 deaths. According to the ten-year observation, the vaccine seemed effective with the protection rate in population reached 100%. CONCLUSION: HFRS vaccine was effective on epidemiological, social and economical efficacy.

[Investigation on vibrio cholera carried in aquatic products of littoral areas, Zhejiang Province].

OBJECTIVE: To examine vibrio cholera (V.C) in aquatic products of littoral area, Zhejiang Province and to provide scientific evidence for administration of aquatic products and cholera epidemic control. METHODS: All 990 samples of aquatic products collected from local markets, eateries and aquafarms in three chosen areas. Samples were proliferated in alkaline liquid medium, and purified in NO: 4 medium, the isolations were identified biochemically, and phenotype of strains were defined by phagocyte and coagulation with V.C. diagnostic serum. Three virulence genes (ctx, ace, zct) of the isolated strains were detected by polymerase chain reaction (PCR). RESULTS: There were 1.41% samples caught by V.C., having a carrying rate highest in turtles of 8.9%. 14 strains were defined as three serogroups, and the numbers of Inaba, Ogawa, and Hikojima types were 2, 2, 10 respectively. Virulence genes had detected in 9 of 12 stains. All genes were detected in 5 strains, only ZOT genes in 3 strains, and both CTX and ACE genes in 1 strain. CONCLUSIONS: Aquatic products from inshore in Zhejiang Province caught with V.C. strains might be divided into three serogroups. Most of them should be virulence genes. Cholera epidemic outbreak might be caused by those contaminated products.