The Epidemiological Study On Measles Of Jiangsu Province

Objectives: (1) To analyze epidemiological characteristics of measles in Jiangsu Province and to provide the evidence for strategies and measures of measles prevention and control. (2) To know the level of immunity against measles so as to impose control and supervision to monitor the process of the measles elimination in Jiangsu Province. (3) To identify the genetic characterizations of wild-type measles viruses in Jiangsu Province, to track out the infection sources, ensure the route of transmition and cut it out scientifically. (4) Modelling ARIMA, using the incidence data that reported by China Information System for Diseases Control and Prevention to forecast the incidence between 2008 to 2012. Establishing the epidemiological model to predict the number of measles cases in the next years of Jiangsu Province and to estimate the reproductive number(R0) from 2008 to 2012. To find out whether the goal of eliminating the measles could be achieved before 2010.Contents: (1) Epidemiological characterizations of measles in Jiangsu Province. (2) Population-based serosurveys in Jiangsu Province. (3) The molecular epidemiological study on wild-type measles viruses in Jiangsu Province. (4)Application of mathematical models on incidence forecasting in measles of Jiangsu Provinvce. Methods: (1) Analyzing the disease distributing of measles with descriptive epidemiology. (2) According to the manufacturer's instructions, sera were tested and interpreted, using German Virion-Serion anti-measles IgG enzyme immunoassay. (3) Vero-SLAM cell was used for measles viral isolation from the throst swabs of measles patients. Fragment of 600 nucleotide acids of the carboxyl end of nucleoprotein gene were amplified using reverse transcription-polymerase chain reaction(RT-PCR) method, and then the PCR products were directly sequenced and analyzed. Phylogenetic analysis and the diversity analysis were done with Bio-Edit. (4) Based on the reported data of measles of Jiangsu Province between 1952 to 2007, model was fitted to check out the sample from 2008 to verify its practicability. A dynamics model of measles, using method of ordinary differential equation, was formulated in order to determined the reproductive number(R0) between 2008 to 2012.Results: (1) The distribution of age among measles patients show evidently to a bidirectional movement. The peak of incidence had changed from 5-9 years age group to less than 1 year age group. Another peak distributed in 25-30 years age group. Most measles cases distributed in the cities which had many floating population instead of those with an undeveloped economy. Seasonal variation was not changed. (2) The seropositive rates and measles IgG levels among age groups had statistical significance. The seropositive rates among regions had statistical significance. Significant differences were found in the seropositive rates among regions in age groups of 0-7 months, 8 months-2 years, 10-14 years, 15-19 years, 30-39 years and 40+ years. In ages 8 months-2 years the seropositive rates were significantly elevated in vaccined than in unvaccined. (3) Two hundred and eleven measles viruses isolated were all identified as H1 genotype, and all belonged to H1a sub-genotype in Jiangsu Province during 2003 to 2008. The averge genetic distance of isolated was 1.79%. The average genetic distance within and between the year showed that the range was 1.59% to 2.64% and 1.19% to 2.84% respectively. (4) The number of measles cases was estimated to be gradually decreasing in the following years in Jiangsu Province, but constantly more than 4000. R0 was estimated to be 2.58 to 3.39 and predicted to greater than 1(the epidemic threshold) until 2012. Assuming the vaccined proportion of susceptible more than 92 percent and other condition stay steadily, R0 will close to 1.Conclusions: Measles epidemiological characterizations had changed a lot in the past decades. H1a sub-genotype was the predominant genotype of wild measles virus circulated in Jiangsu Province, which was the same as the dominant genotype prevalence in other provinces in the mainland China. The aim of measles elimination cannot be achieved if the immunication strategies unchanged. To carry out the goal, the timeliness and coverage of childhood vaccinations should be improved and innovative strategies will be required to improve measles immunity among babies and adults.