| ObjectiveThis research was aimed at evaluating the Measles Surveillance System in border areas of "Yunnan province to understand the running status of Measles Surveillance System and to find the problem existed. It was also aimed at revealing the epidemic characteristics of measles in border areas of "Yunnan province and illustrating the situation of measles outbreak and import epidemic while acquiring the gene type features of measles virus strains, cross-border imported measles cases and the distribution of imported genotypes in border areas of Yunnan province according to the molecular biologic surveillance. The research as to provide scientific basis on the measures of measles elimination and prevention for the import epidemic of measles in the "Yunnan province and border areas.MethodsMain performance indicators of MSS were evaluated according to the investigation and analysis of measles cases surveillance data that reported by border areas of Yunnan province through MSS during 2014-2015. Epidemic characteristics of measles and the epidemic situation of measles outbreak were analyzed and described by the methods from description epidemiology, which included field investigating, data collecting and processing. Data were summarized and analyzed by Excel 2007 and SPSS 17.0 software. The strains of measles from border areas in Yunnan province were cultured by virus proliferation used the Vero/SLAM cells, and the virus nucleic acids were extracted and identified by the method of Real-time fluorescence quantitative RT-PCR. The measles virus N gene fragments was amplified by the method of reverse transcription-polymerase chain reaction (RT-PCR), amplification products were identified by agarose gel electrophoresis and were sent to be purified and sequenced by biotechnology companies. Gene sequences were compared with 450 nucleotide sequences at the terminal of N Gene carboxyl with the WHO representative strains. Gene sequences affinity and phylogenetic analysis were conducted by MEGA 5.0 software.Results1 The operating conditions of MSSAccording to the diagnostic criteria for classification,928 cases of suspected measles were reported during the year from 2014 to 2015 while 799 cases excluded. The average rate of IDMC was 58.7/million, and the incidence of discarded measles and rubella cases was 49.8/million.The integrated investigation rate of individual case within 48 hours was 97.52%, the rate of case information inputting within 48 hours was 78.66%, deliverability rates of specimen within 3 days was 97.03%. And after the specimen received, the report rate within 4 days was 80.22%, the rate of blood specimens collecting for surveillance measles cases and sporadic cases that supervised by measles surveillance system was 97.20% and 98.30%. Serology confirmed rate of break cases was 100.0%, and pathogen specimen collected rate of the break measles cases was 83.33%. Overall, the sensitivity and specificity of MSS was high, but the promptness was unsatisfied while the collected rate of the second serum specimen was lower, both of the pathogen specimen collected rate and detection rate were low, and there existed the phenomenon that excluded measles cases by the serology results of the first serum specimen that collected after eruption within 3 days or excluded measles infection without laboratory confirming; we also found that some of CDC staffs are not familiar with the monitoring program, the measles epidemics disposal tasks implementation did not reach the position designated, And a small part of medical institutions omitted the reporting of suspected measles cases.2 Epidemic characteristics of measles casesThere were 129 confirmed cases of measles were reported during the year from 2014 to 2015, and the average incidence rate per year was 9.5/million. Most cases of measles cases emerged in the season of spring to early summer and late autumn (from February to May, and October to November). The number of reported cases in spring and the early summer autumn season was 96, which accounted for 75% of the total measles cases in the whole year. And measles became high epidemic of outbreaking since October. The high prevalence regions of measles included the Funing county that border on Vietnam, Malipo county and Cangyuan county that border on Myanmar, the numbers of reported measles cases and incidence in these county was 46 (52.2/million),27 (47.6/million) and 15 (41.2/million). And these cases that reported in these counties accounted for 68.22% of the total reported cases in border areas. On the features of epidemic, measles outbreak in Malipo while it was sporadic in Cangyuan, and both of these two styles of epidemic models co-existed in Funing. There were 83 cases of measles reported in the China-Vietnam border areas while 44 cases reported in the China-Myanmar border areas and 2 cases in the China-Laos border areas. The onset age of measles collected in the age group from 8 months to 6 years old, which accounted for 48.84% among peoples whom covered by the immunization program, while the incidence of measles among younger age group and adults had been increasing gradually, and the incidence rate was 237.9/million among patients from the age group of< 1 years old, and the incidence was the highest among all age groups. Occupational distribution showed a concentration of cases in scattered children and farmers. There were only 33 cases (25.58%) of measles reported history of immunization among all the measles cases and 49 cases (37.98%) reported history of treatment in medical institutions before measles attacked within 7 to 21 days, while 21 cases (16.28%) of measles were from migrant populatioa There were 42 outbreak cases of measles reported from 6 times of measles outbreaks from border areas, which accounted for 32.56% of the total reported cases. The outbreak cases concentrated in scattered children, farmers and students, and the place of outbreaks mainly clustered in families, schools and kindergarten and nursery organizations.10 imported cases were detected,9 cases of them were Burmese, and the other one came from Laos, The epidemic situation of measles input was serious.3 Laboratory examine results of measles casesThere were 77 pieces of measles’ pathogen specimen received by the provincial laboratory during the year from 2014 to 2015. After virus cultivation, nucleic acid abstraction and amplification of RT-PCR,23 pieces of specimen were detected positive bands at the site of 700 bp in AGE (agarose gel electrophoresis), and nucleic sequences acquired. The results of gene sequencing showed that among 23 pieces of specimen,15 pieces of specimen were H1 genotype strains,4 pieces of specimen were D9 genotype strains and 4 pieces of specimen were A genotype strain. All the 15 piece of HI genotype strains all belong to H1 a subtype which was the predominant genotype strain in Yunnan province. Further analysis showed that Chinese border’s H1 genotype strains were in the same transmission chain with "Vietnamese. D9 strains that detected in this research were imported from Myanmar and there existed a common D9 genotype transmission chain in the border areas between China and Myanmar while D9 genotype strains transmitted interactive between Chinese and Burmese borderline. H1 a and G9 genotype strains co-existed and circulated in border areas, while the 4 strains of A genotype were the vaccine related strains.ConclusionsMSS running well in border areas of Yunnan province, but some of counties in borer areas did not strictly implement the surveillance of measles according to the monitoring programs and schedules. Both the collected rate of the second serum specimen, pathogen specimen collected rate and detection rate were low, the productivity and quality of surveillance should be enhanced. Measles incidence rates were still on high level, but the effects of measles control in 2015 were much more better and satisfied compared with 2014, according to the change of numbers of measles infection, incidence rate, frequencies of outbreak, numbers of outbreak cases, numbers of counties that had measles cases reported and the temporal distribution. The levels of immunization programs were variant and unbalanced in different border area counties, and the prevention for measles were weak and insufficient among peoples in some areas. The onset age of measles infected was mainly concentrated in people who at the age of immunization stage while scattered children and farmers were susceptible to measles, incidence rates were higher among peoples who had no MCV immunization history and migrant peoples, and nosocomial infection also existed. H1 a gene subtype and D9 genotype strains were circulated in the border area, which was similar to the epidemic situations in the neighboring countries, and the condition of strains importing deserved to be alarmed. Further more, Training and guidance to the basic CDC staffs and health personnel should be strengthened that to ensure the quality and status of detailed epidemic investigations and serious laboratory examinations and to increase the sensitivity of MSS. The advertisement and education on prevention to infectious diseases should be strengthened in some key areas, especially in border areas. To strengthen the management of the floating children and routine immunization vaccination work, SIAs or leak seeding work should be taken that to achieve and maintain high levels of routine immunization MCV coverage; Also we should strengthen the guidance of the hospital infection prevention and control work, And the implementation of the schools or other kindergarten and nursery organizations check the immunization certificate inspection seeding work before entrance that prevent and avoid nosocomial infection and measles epidemic in school. The epidemiological and laboratory surveillance in border areas should be emphasized to report the imported cases in time and prevent the epidemic or transmission cross border. |
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