Population-Based Estimate of the Burden of Acute Gastrointestinal Illness in Jiangsu Province, China, 2010–2011
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Epidemiol. Infect. (2013), 141, 944–952. f Cambridge University Press 2012 doi:10.1017/S0950268812001331 Population-based estimate of the burden of acute gastrointestinal illness in Jiangsu province, China, 2010–2011 Y. J. ZHOU 1,Y.DAI1,B.J.YUAN1,S.Q.ZHEN1,Z.TANG1,G.L.WU1,Y.WANG1, M. H. ZHOU 1* AND Y. CHEN 2* 1 Institute of Food Safety and Assessment, Jiangsu Provincial Center for Disease Control and Prevention, Nanjing, People’s Republic of China 2 China National Center for Food Safety Risk Assessment, Beijing, People’s Republic of China Received 31 October 2011; Final revision 28 April 2012; Accepted 31 May 2012; first published online 16 July 2012 SUMMARY To determine the burden and distribution of acute gastrointestinal illness (AGI) in the population, a cross-sectional, monthly face-to-face survey of 10 959 residents was conducted in Jiangsu province between July 2010 and June 2011. The adjusted monthly prevalence was 4.7% with 0.63 AGI episodes/person per year. The prevalence was the highest in children aged <5 years and lowest in persons aged o65 years. A bimodal seasonal distribution was observed with peaks in summer and winter. Regional difference of AGI prevalence was substantial [lowest 0.5% in Taicang, highest 15.1% in Xinqu (Wuxi prefecture)]. Healthcare was sought by 38.4% of the ill respondents. The use of antibiotics was reported by 65.2% of the ill respondents and 38.9% took antidiarrhoeals. In the multivariable model, gender, education, season, sentinel site and travel were significant risk factors of being a case of AGI. These results highlight the substantial burden of AGI and the risk factors associated with AGI in Jiangsu province, China. Key words: Acute gastrointestinal illness, cross-sectional studies, epidemiology. INTRODUCTION portant. In the USA about 179 million episodes of AGI occur each year and result in 600 000 hospital- Acute gastrointestinal illness (AGI), usually present- izations and 5000 deaths [3, 4]. Although AGI is ing as diarrhoea and vomiting, is a common and im- usually self-limiting, due to the high annual number portant public health problem worldwide [1]. It is of individuals affected, illness imposes a substantial recognized as one of the leading causes of morbidity economic burden upon the population and healthcare and mortality in developing countries, especially for system [5]. children aged <5 years [2]. While AGI mortality is Although AGI is very common in the community, low in developed countries, AGI morbidity remains cases of AGI tend to be under-reported by traditional im- surveillance, which requires cases to present to the healthcare system. To address this, several * Author for correspondence: Dr Y. Chen, China National Center population-based studies have been conducted in for Food Safety Risk Assessment, 7 Panjiayuan Nanli, Chaoyang developed countries in order to obtain more accurate District, Beijing 100021, People’s Republic of China. (Email: [email protected]) [Y. Chen] estimates of incidence [6–9]. Measuring the actual (Email: [email protected]) [M. H. Zhou] disease burden within the population is important Downloaded from https://www.cambridge.org/core. IP address: 170.106.35.234, on 27 Sep 2021 at 12:51:08, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0950268812001331 Gastroenteritis in Jiangsu, China 945 Beijing CHINA Study area Xuzhou JIANGSU PROVINCE Yellow Sea Yizheng Taizhou Liyang Jiangyin Changshu Wuxi Taicang Suzhou Sampling sites Fig. 1. Map of the sampling sites in Jiangsu province, China. for understanding of disease dynamics and guiding their suitability, willingness of local authorities and prevention strategies for gastroenteritis, especially feasibility of completing the studies. The sentinel sites foodborne diseases. were: (i) Xinqu (Wuxi prefecture) (population In China, information on AGI comes mainly 404 573), (ii) Quanshan (Xuzhou prefecture) (popu- from hospital-based or laboratory-based surveillance lation 615 007), (iii) Canglang (Suzhou prefecture) [10, 11]. To adjust hospital-based measurements of (population 325 696), (iv) Hailing (Taizhou prefec- the burden of AGI in China, the Chinese Center for ture) (population 374 267), (v) Jiangyin (population Disease Control and Prevention launched a national 1 420 105), (vi) Changshu (population 1 066 400), population-based study on AGI in 2010. The data (vii) Taicang (population 538 506), (viii) Liyang presented in this paper are from a subsample of par- (population 765 842) and (ix) Yizheng (population ticipants from Jiangsu province. We conducted the 608 092). The sentinel sites represent about 7.9% first community survey to estimate the number of of the total Jiangsu permanent resident population cases of AGI in Jiangsu province, China between July (77 250 011) in 2009. 2010 and June 2011. The objectives of the present Each sentinel site was divided into several blocks study were to determine the temporal and demo- in terms of population proportioned distribution. graphic distribution of AGI in the population, inves- In total, we generated 693 blocks from the nine sen- tigate the burden of self-reported AGI, describe tinel sites. Households were randomly selected from healthcare-seeking behaviour for AGI and identify each block and the number of households surveyed risk factors associated with AGI. was proportional to population size. Within each household, one individual with the next birthday was selected to participate in the survey. Up to three at- METHODS tempts were made to contact the selected individual at different times of the day to complete the survey. Study design and sample If the selected individual declined or no one lived at A cross-sectional, face-to-face survey was adminis- the residence, the neighbouring house (i.e. the nearest tered from July 2010 to June 2011 within nine residence), was selected as replacement. Proxy purposively selected sentinel sites in Jiangsu province respondents were used for all children aged <12 years (Fig. 1). The sentinel sites were selected based on and for individuals aged 12–18 years when parental Downloaded from https://www.cambridge.org/core. IP address: 170.106.35.234, on 27 Sep 2021 at 12:51:08, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0950268812001331 946 Y. J. Zhou and others consent was not given to interview them directly. each sentinel site each month. All the data analyses Written and informed consent was obtained from all were performed using the software package SPSS, respondents before the interview. Surveys were ad- version 16.0 (SPSS Inc., USA). ministered in Chinese. Response rate was calculated by dividing the num- A target sample size of 1110 interviews per region ber of completed surveys by the number of house- was calculated to detect a prevalence of 7%, with a holds visited. The monthly prevalence of AGI was 5% level of precision and a 1.5% allowable error. calculated as the number of respondents reporting This translated into a total of 9990 interviews, with an AGI in the 4 weeks prior to the interview divided by overall allowable error of 0.5% (Epi Info v. 3.0.2; the total number of respondents. The incidence rate CDC, USA). To achieve this target, about 93 inter- of AGI/person per year was calculated using the ter- views were completed each month for each sentinel minology and formulae outlined by Rothman & site over a 12-month period. Greenland [7, 12, 13]. These estimates were adjusted for known differ- Data collection ences between the survey sample and the target population by weighting for age and sex using the fifth Household interviews were performed by trained national population census data of Jiangsu province healthcare workers using a standard questionnaire. as the reference population. The x2 test was used for The questionnaire was validated and developed testing the association between demographic factors specifically for the purposes of this study. All and the occurrence of AGI. Mean duration of diar- respondents were asked if they suffered from diar- rhoea with respect to different age groups was rhoea, or vomiting in the 4 weeks prior to the inter- compared by analysis of variance (ANOVA). Values view. If the respondent reported diarrhoea or of P<0.05 were considered statistically significant. vomiting, they were asked for more details regarding Multivariable logistic regression was used to estimate symptoms and timing, what they thought had caused odds ratios (ORs) for each of the geographical, their illness, travel to other city/province, the use demographic variables. Weighting was not included of medical consultation and treatment, admission in the logistic regression since the purpose of the to hospital and whether a stool sample was sent analysis was to identify relative ORs among risk fac- for diagnostic purposes, the social and economic im- tors. In multivariable analysis, to determine the vari- pact of illness, and illness in other members of ables in the model we used the forward elimination the household. Additional questions were asked about method. Explanatory variables tested were gender, demographic factors, including the respondent’s sex, age, education, occupation, household size, house- age, information on household size and occupation. hold type, residence, season, sentinel site and travel history. Variables with P<0.05 were included in the Case definition final model. AGI was defined as diarrhoea of o3 loose stools in a 24-h period or significant vomiting with at least one other symptom (abdominal pain/cramps, fever). All RESULTS analyses excluded those persons who considered their Response rate and prevalence of AGI symptoms to be due to non-infectious causes of diar- rhoea or vomiting such as Crohn’s disease, irritable The overall response rate was 87% with 10 959 bowel syndrome, ulcerative colitis, excess alcohol, completed interviews.