| ObjectiveBy exploring various layered schemes, on the basis of determining different layered schemes, the numbers of newly-infected hepatitis C virus (HCV) were estimated by gender and age-group during 2007-2014 in China. The results from the study could be used to understand of HCV infection status and imply policy-making for the strategy of HCV control and prevention. Moreover, it could provide statistical method of the estimation of newly-infected HCV cases for similar infectious diseases with a new idea and estimated method in the future.MethodsReported incidence of cases of hepatitis C during 2007 and 2014 across China, the national communicable disease reporting quality of survey results in 2005,2009 and 2014, an outbreak data of HCV from the clinic in a county, and social and economic indicators associated with the development of HCV in 2012 at the city level were collected for the use of the study.First, sorting out and analyzing numbers of reported cases of the hepatitis C at the city and county levels by sex and age group, after corrected numbers of reported incidence of HCV, adjusting for the hospital and community under-reporting rates of HCV.Secondly, due to the presence of spatial heterogeneity in the distribution of hepatitis C virus, different layers of urban residents per capita disposable income, rural per capita net income, and per capita gross domestic product (GDP), corrected reported incidence rate of HCV at the level city, and corrected reported incidence rate of HCV at the county level were explored; five layered schemes of the optimal layer from each indicator were determined according to Pd values.Thirdly, constructing an relational function of the corrected numbers of reported incidence of the disease with incubation period of HCV and newly-infected function of HCV; backcalculation of infection rates (BIR)was used with the expectation maximization algorithm (EM); in the above optimal five layered schemes and provincial administrative divisions, numbers of newly-infected cases and rates of HCV during 2007 and 2014 by sex and age group were estimated.Finally, at the national and provincial levels, numbers of newly-infected HCV cases, rates and standardized rates by year, gender and age group were presented; these numbers were compared with corresponding numbers of reported incidence rates for the same period.ResultsOverall, under the 5 optimal layered schemes and in provincial administrative divisions numbers of newly-infected cases of HCV and trends by year were similar, The estimated results under five optimal layered schemes demonstrated that the total numbers of newly-infected cases of HCV were about 3,080,339～3,104,690, which was more than 2.3 times the numbers of reported incidence of HCV during 2007 and 2014. During 2007 and 2014, the numbers of newly-infected cases of HCV (standardized rate) showed a general upward trend, average value of 232.1 thousand (18.30/100,000 for the standardized rate) in 2007 increased to nearly 500 thousand in 2014 (36.43/100,000 for the standardized rate).The estimated numbers of newly-infected cases of HCV (standardized rate) during 2007 and 2014 by gender and age group under the five layered schemes were similar:first of all, from the view of gender, the gender proportion of the standardized rates of the newly-infected cases of HCV across the five layered schemes were similar, the gender proportion between the standardized rates of the newly-infected cases of HCV were similar compared to the reported incidence rate of HCV; male standardized rate of the newly-infected cases of HCV was higher than that of females, but the differences between the two was decreased with years.Secondly, from the view of age group, from 2007 to 2014, except for the newly-infected rate of HCV in 5-14 years group was relatively stable, other age groups demonstrated a upward trend; the number of newly-infected cases of HCV (standardized rate) in 15-49 age group was the highest among all of the age groups, the number of newly-infected cases of HCV was up to a maximum of 277,908 and the standardized rate of the newly-infected cases of HCV was reached to 20.75/100,000, which was the main infection population of HCV.In Xinjiang, Qinghai and Henan provinces, the newly-infected rates of HCV were higher than those in other provinces during 2007 and 2014. The newly-infected rate of HCV in the eastern provinces was lower than those in the central and western regions. During 2007 and 2014, the annual number of newly-infected cases of HCV in the provinces was higher in men than that in women, especially in 15-49 years old and 50～69 years old groups.ConclusionIn our country,the number of infection cases of HCV about 3.1 million, more than twice the number of reported incidence of HCV during 2007-2014,which showed that the actual existence of a large number of infection cases of HCV do not reported,those will greatly threaten human health and increase the burden of disease caused by HCV.During 2007 and 2014, the numbers of newly-infected cases of HCV (standardized rate) showed a upward trend with years.Male standardized rate of the newly-infected cases of HCV was higher than that of females, but the gap between the two rates were decreased with years. The number of newly-infected cases of HCV (standardized rate) in 15～49 age group was the highest among all of the age groups, which was the main infection population of HCV. Meanwhile,the spatial distribution of the newly-infected rate of HCV was not even.The newly-infected rate of HCV in the eastern provinces was lower than those in the central and western regions.The space layered estimating of newly-infected cases of HCV could improve the estimation efficiency.This study show the result of the different layered schemes estimates roughly the same, suggesting that choose the most accessible and quality data layered according to the actual situation in future public health practices, estimating the newly-infected cases of HCV. |
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