| Typhoid and paratyphoid are acute enteric communicable diseases transmitted by fecal-oral route, of which pathogenies are Salmonella typhi and Salmonella Paratyphoid ABC. According to"China Law of Communicable Disease Control", they belong to type B of infectious diseases.Typhoid and paratyphoid spread all over the world, but most of cases are in developing countries.Worldwide, the estimated new cases and dealths per year are 16 millions to 17 millions and 0.6 millions respectively. In China, the incidence rates of typhoid fluctuated between 10.00 per 100 thousand and 50.00 per 100 thousand before 1990, and decreased to the range of 4.08 per 100 thousand and 10.45 per 100 thousand after 1990. However, paratyphoid A broken out constantly, and the number of cases increased rapidly since 1995.Worldwide typhoid and paratyphoid took place in break out with a high frequency. Many researches have been conducted to explore the risk factors and concluded that the major factors of the outbreaks were lack of public health facilities, water and food contaminations.In China, Zhejiang is one of the high-incidence provinces. The incidence of typhoid and paratyphoid re-increased in recent years with local outbreaks and epidemics frequently. Through describing and analyzing the epidemic status of typhoid and paratyphoid, the objective of the study is to explore their epidemiological characteristics and prevalent rules, as well as main risk factors and prevention andcontrol measures in Zhejiang Province.Materials and methodsData of provincial typhoid and paratyphoid epidemics and incidence of floating population from 1953 to 2003 were obtained from datum collections of communicable disease epidemics of Zhejiang Province, data of provincial typhoid and paratyphoid epidemics during 2004 to 2005 from online direct reporting system of China center for disease control and prevention(CDC), the outbreak data from Zhejiang CDC . All data were settled and analyzed according to distributions of population, region and time characteristics,.According to GB16001-1995 , cases were diagnosed by multi-grade hospitals. Laboratory work were done by experienced experimenters.The investigation of risk factors was carried out in Wenling city of Zhejiang province. 1:1 matched case-control studies were adopted . Cases were paratyphoid A patients undergoing laboratory diagnosis. Controls were selected from healthy people, which never infected typhoid or paratyphoid, and matched with cases by sex, age, occupation and residence.Applying uniform-made questionnaires that were pre-investigated first, face-to-face interviews were carried out by interviewers that had received uniform training. Investigation contents included general characteristics, dietary habits, dietary 10 days before infection, health habits, drinking water etc..All questionnaires were uniformly coded, and the database was established by means of Excel. Cross-sectional analysis and case-control study were done after checking data. Cross-sectional analysis included epidemic characteristics of typhoid or paratyphoid in Zhejiang province and Wenling city. In the case-control study, we focus emphasis on risk factors, such as diet and drinking water. Group analysis, pair analysis and conditional Logistic regression were done.All statistical analysis was processed in softwares of Excel ,EPI-INFO 2002 and SPSS 12.0.ResultsPart I. Epidemical characteristics of typhoid and paratyphoid in Zhejiang provinceIn the 1950s, the average incidence rate of typhoid and paratyphoid in Zhejiang province was 12.40 per 100 thousand. The average incidence rate was 6.19 per 100 thousand in the 1960s, 3.18 per 100 thousand in the 1970s and 8.27 per 100 thousand in the 1980s. The incidence rate increased abruptly in 1986 and exceeded 10 per 100 thousand from 1987 to 1994. In 1990, the incidence rate was 19.04 per 100 thousand.In 1995, the incidence rate of typhoid and paratyphoid was 9.76 per 100 thousand in Zhejiang province. The incidence rate was around 10.00 per 100 thousand from 1996 to 1999 . However, during 2000 and 2004, the incidence rate increased yearly. In 2004, outbreaks emerged in some regions and the incidence rate reached 17.52 per 100 thousand, which was up to the peak of past years. In 2004, the cases of typhoid and paratyphoid were respectively 2665 and 5567.Taizhou, Wenzhou, Shaoxing, Jinhua and Ningbo city always had the high incidence rates of typhoid and paratyphoid in recent years. Incidence rates of the above regions exceeded 10 per 100 thousand after 2000. The incidence rate of typhoid and paratyphoid in Taizhou, which had the most severe epidemic situation was 61.56 per 100 thousand in 2004 year.With economy development in Zhejiang province, more and more floating population entered. The cases of typhoid and paratyphoid increased with a large annual range.During July to October, typhoid and paratyphoid had a higher incidence rate in Zhejiang province. However, in 2004 and 2005, there had been two peaks of incidence rates due to some outbreaks, among which one is January and April, another is July to October.From the beginning of 2001, the main pathogeny of typhoid and paratyphoid was salmonella paratyphi A instead of previous Salmonella typhi. In 2004, 94.74% of total pathogenies were salmonella paratyphi A.There had 12 outbreaks of typhoid and paratyphoid in Zhejiang province in 2004. Four of them were occurred in Taizhou city. In Wenlin, there was an outbreak of paratyphoid disease from January to April.Part II. Risk factors of typhoid and paratyphoid in Zhejiang provinceWe analyzed the epidemic situation and done a field epidemiology study in Wenling .In the case-control studies, we found that having breakfast(OR=2.70, 95%CI: 1.32-5.59) and frequency(OR=9.00,95%CI: 1.12-17.13), having lunch and supper(OR = 3.88 ,95%CI: 1.90-8.12), having repasts at outdoor within 1-10 days(OR = 4.62 , 95%CI: 2.20-9.90) would increase the risk of infecting paratyphoid and had dose-response relationships. In addition, the style of eating seashell was a risk factor too (0R=11.49, 95%CI: 2.82—46.76) .Using hierarchical analysis, it was found that eating uncooked bloody clam(OR=5.04, 95%CI:1.05~24.30) and jellyfish (OR=10.81, 95%CI: 1.34—88.92)were the important risk factors. After the analysis of hierarchical analysis, we alsofound that using well water was an important risk factor at Taiping district of Wenling(OR=3.62, 95%CI: 1.56—8.41) .Using conditional Logistic regression of multiple factors, we found that eating uncooked and half cooked seashell (OR=4.61, 95%CI:1.08—19.58), as well as having lunch and supper at outdoor(OR = 1.71, 95%CI : 1.04—2.82), were risk factors in Wenling.ConclusionsThis study indicates that typhoid and paratyphoid has been at the peak period of prevalence since 2001 in Zhejiang Province. Taizhou, Wenzhou, Shaoxing, Jinhua and Ningbo have quite high incidence rates of typhoid and paratyphoid. Nowadays, the main type of cases in Zhejiang province is paratyphoid A.In history, most cases of typhoid and paratyphoid came from the north Zhejiang where are plain and water-rich region , such as Jiaxing and Huzhou. However, the regions in east-south of Zhejiang, such as Taizhou and Wenzhou, which had a large number of floating population and their incidence rates increased obviously. Among typhoid and paratyphoid cases, the proportion of floating population increased yearafter year.Water pollution, especially well water, is the main reason of outbreaks of typhoidand paratyphoid that happened in populous region such as schools. In coastland such as Wenling, food, especially aquatic product (such as Oyster and blood clam) is the important reason of sporadic and epidemic of typhoid and paratyphoid, which will cause the high incidence rate around the New Year's day and Spring Festival.The epidemic situation of paratyphoid A that happened in Wenling in 2004 was a local prevalence with a wide sporadic characteristic . Drought and short of water are the main reasons that result in the prevalence, and eating fresh or half-cooked shellfish and well water are main risk factor.This study also indicates that the epidemic situation of typhoid and paratyphoid is a important problem of public health in Zhejiang province. We should focus the emphases on researches of risk factors causing outbreak and prevalence and searching for the best prevention and control measures.
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