An outbreak of type π vaccine-derived poliovirus in Sichuan province, China: emergence and circulation in an under-immunized population.

BACKGROUND: During August 2011-February 2012, an outbreak of type Π circulating vaccine-derived poliovirus (cVDPVs) occurred in Sichuan Province, China. METHODS: A field investigation of the outbreak was conducted to characterize outbreak isolates and to guide emergency response. Sequence analysis of poliovirus capsid protein VP1 was performed to determine the viral propagation, and a coverage survey was carried out for risk assessment. RESULTS: One clinical compatible polio case and three VDPV cases were determined in Ngawa County, Ngawa Tibetan and Qiang Autonomous Prefecture, Sichuan Province. Case patients were unimmunized children, 0.8-1 years old. Genetic sequencing showed that the isolates diverged from the VP1 region of the type Π Sabin strain by 5-12 nucleotides (nt) and shared the same 5 nt VP1 substitutions, which indicate single lineage of cVDPVs. Of the 7 acute flaccid paralysis cases (all>6 months) reported in Ngawa Prefecture in 2011, 4 (57.1%) cases (including 2 polio cases) did not receive oral attenuated poliovirus vaccine. Supplementary immunization activities (SIAs) were conducted in February-May, 2012, and the strain has not been isolated since. CONCLUSION: High coverage of routine immunization should be maintained among children until WPV transmission is globally eradicated. Risk assessments should be conducted regularly to pinpoint high risk areas or subpopulations, with SIAs developed if necessary.

[Investigation on the source of infection regarding an avian influenza (H5N1) case in Hong Kong that returning from Guangzhou].

OBJECTIVE: We conducted an epidemiologic investigation to determine the source of infection on an avian influenza (H5N1) case who returned from Guangzhou, in Hong Kong. METHODS: Data related to epidemiologic investigation, medical observation on close contacts, Syndromic Surveillance on poultry salesmen, emergency monitoring, detection of the samples, source tracing on potential Avian influenza virus (H5, H7, H9) infected people, situation on environment pollution by avian influenza virus in the markets etc. were gathered. The determination of infection source was through comparing the different genes between the case and positive environmental samples. RESULTS: The infected case witnessed the procedure of how a live duck was killed, in market A in Guangzhou during May 17(th) to 19(th). The case was diagnosed as respiratory tract infection in 2 Third-grade-Class A hospitals in Guangzhou on May 23(th) and 24(th). The diagnosis was made as Avian influenza cases on May 26(th) after going back to Hong Kong. 23 close contacts and 34 markets poultry salesmen did not show any ILI related symptoms. However, 2 poultry salesmen from the markets nearby the place where the Avian influenza case stayed, were detected having positive H9 avian influenza antibody, with the H9 positive rate as 6.06% (2/33). Among the environmental samples in the 2 markets nearby home of the patient, chopping block was found to have carried H5, with positive rate as 9.8% (5/51) while poultry cage was found to carry H9, with the positive rate as 2.0% (1/51). A H5 positive sample was found with clade 2.3.2.1, same to the case, from a chopping block at the market B where the sources of poultry was the same as market A. CONCLUSION: The source of infection seemed to come from the markets in Guangzhou, that calling for the strengthening of poultry market management, for avian influenza prevention. History related to contact of poultry should be gathered when a diagnosis of respiratory tract infection was made. Timely sampling and testing should be made to improve the sensitivity of diagnosis.

[A seroepidemiologic analysis of hepatitis B in Sichuan province].

OBJECTIVE: To understand the changes of hepatitis B infection rates, before and after the hepatitis B vaccine was included into EPI, and to evaluate the effect of immunization which would lead to the development of a more appropriate hepatitis B control strategy. METHODS: Seroepidemiologic method, with multi-section random sampling method were chosen. 14 sites from 8 counties were involved. 2-4 ml of the vein blood was drawn from all the individuals engaged in the study including 3806 samples. HBsAg, anti-HBs, anti-HBc of the samples were tested with ELISA. RESULTS: Standardized positive rates of HBsAg and HBsAb were found as 7.05% and 29.77% respectively with the overall infection rate of HBV as 40.30%. The hepatitis B vaccine coverage of the children under 15 years was 70.73% and the positive rates for both HBsAg and anti-HBs were 2.62% and 56.68%, respectively. The coverage of hepatitis B vaccine among children under 3 years was 83.44% and the positive rates of both HBsAg and anti-HBs were 1.47% and 67.69% respectively, hepatitis B vaccine coverage of children under 3 years was 85.77%, with positive rates of HBsAg and anti-HBs as 1.78% and 75.44% respectively. CONCLUSION: Results from our study revealed that since the introduction of hepatitis B vaccination, the prevalence rates of HBsAg and HBV infection had an obvious decline, especially in children aged under 15 years of old, suggesting that some changes had occurred in the epidemic characteristics of hepatitis B in Sichuan.

[The immunogenicity and safety of 10 microg recombination yeast hepatitis B vaccine applied in expanded population].

OBJECTIVE: To assess the feasibility of the 10 microg recombination yeast hepatitis B vaccine in the expanded applicable population group aged 5 - 18. METHODS: People with both HBsAg and anti-HBs negative were selected to take two-stage clinical experiment and the safety and immunogenicity were observed. Safety observation was conducted in 925 subjects, while 568 for immunogenicity. The observation group (aged 5 - 18) included 493 subjects, and (age > 18) 75 enrolled in control group. For the observation group, there were three sub-groups including a child group (141, aged 5 - 6), early youth group (177, aged 12 - 13), and youth group (175, aged 16 - 18). Both groups were administered with 10 microg recombination yeast hepatitis B vaccines with 3 doses at 0 month, 1st month, 6th month. To assess the immunogenicity, the vaccination reactions were observed during the following 4 weeks in order to assess the vaccine safety. The blood samples were taken during 4 - 6 weeks after fully vaccinated, and then anti-HBs were tested with RIA and analyzed by comparing the positive rate of anti-HBs, the geometric mean titer (GMT) and the protective rate between the two groups. RESULTS: Both observation and control group didn't show any general reactions, adverse events following immunization (AEFI) or coincidental cases when observed at 0.5 h, 6 h, 24 h, 48 h, 72 h, 1 week, 2 weeks, 3 weeks, 4 weeks after being vaccinated. The result of serum test showed, the positive rates of child group, early youth group, youth group and control group were respectively 100.00% (141/141), 97.18% (172/177), 98.29% (172/175) and 89.33% (67/75); the GMTs of anti-HBs were respectively 440.28, 875.38, 467.80, 131.06 U/L; the protective rates were respectively 100.00% (141/141), 97.18% (172/177), 97.14% (170/175) and 86.67% (65/75). The positive rate, GMT and protective rate of the experimental group were all higher than that of control group (chi(2)(positive rate) = 12.77, 5.12, 7.99; t(GMT) = 3.89, 4.13, 5.91; chi(2)(protective rate) = 16.81, 8.60, 8.44; P < 0.05). CONCLUSION: This vaccine could be expanded to 5 - 18 year-old population with safety and effectiveness, the positive rate and protective rate of anti-HBs were both higher than that of control group.

[Analysis on the adverse event following immunization (AEFI) after supplementary immunization activity of measles attenuated live vaccine in Sichuan province in 2007-2008].

OBJECTIVE: To analyze the characteristic and regular patterns of AEFI after Supplementary Immunization Activity (SIAs) of Measles Attenuated Live Vaccine in Sichuan Province in 2007-2008, to discuss the safety of MV SIAs and measures of reducing occurrence of AEFI. METHODS: The descriptive epidemiology analysis on related indexes were conducted. RESULTS: 59 cases of serious AEFI were reported in MV SIAs in 2007-2008. The incidence rate was 4.13/million dosage, and male was higher than female; The incidence between age groups was no significant statistics differences (chi2 = 0.53, P>0.05); people occurrencing serious AEFI within 2 days after vaccination accounted for 3/4. Allergic reaction dominated the clinical damage. Most of the cases were cured. CONCLUSION: Incidence of serious AEFI after MV SIAs was low. It is safe to conduct MV SIAs. Children of all age groups should be observed within 2 day after vaccination. To guarantee the smooth conduct of MV SIAs, we should strengthen AEFI surveillance and improve the skill for handling with serious AEFI.

[Antibody detection and sequencing analysis of hepatitis E virus in human population, swine and chicken in Sichuan region in China].

OBJECTIVE: To investigate the seroprevalence of HEV infection and genotype. METHODS: ELISA were used for detecting anti-HEV IgG of the serum samples, the nested reverse transcriptase PCR (RT-nPCR) was used for detecting HEV RNA in patient serum and swine bile samples. All samples were collected in 2005-2007 in some districts in Sichuan province. The primers used for genotyping were the ORF2 region of HEV genome. RESULTS: The anti-HEV IgG was detected positive in childrens 6.10% (41/672), adults 42.26% (280/ 661), swines 88.89% (32/36), chickens negative (0/59). 1 case of 15 serum samples of anti-HEV IgM positive and 3 of 54 swine bile samples were positive for HEV RNA by RT-PCR.Sequence analysis of 4 isolates has 92.1% to 98.6% nucleotide sequence homology. These isolates from human and swine were identified closely related to Ch-T21 strain 90.1%-96.9% sequence homology, which belonged to HEV genotype 4B. CONCLUSIONS: The swine were the risk factors in the spread of hepatitis E virus.