传染病暴发调查

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1、实习七 爆发调查一、疾病爆发（一、疾病爆发（disease outbreak）图 13-2 点源爆发的流行曲线 因为点源流行的流行曲线近似对数正态曲线，所以 )(log)log()log(log2bxax xxbxx-axxbxaxx （13-1）)()()(10020210mmmmmmmmababx （13-2）xmt0 （13-3）三、爆发调查的主要目的三、爆发调查的主要目的确定疫情性质，就是确定本次爆发的性质确定疫情性质，就是确定本次爆发的性质查清爆发危害程度，就是疾病三间分布查清爆发危害程度，就是疾病三间分布查明病因和爆发影响因素，如传染源和传播途径等查明病因和爆发影响因素，如传染源和

2、传播途径等确定高危人群，并且予以有效的保护确定高危人群，并且予以有效的保护制定切实措施，控制疾病爆发和流行，并总结经验制定切实措施，控制疾病爆发和流行，并总结经验教训，避免此类事件再次发生教训，避免此类事件再次发生在多数情况下，首先根据经验采取常规初步措施，然后在爆发在多数情况下，首先根据经验采取常规初步措施，然后在爆发调查过程中不断修正。爆发调查中的干预主要是实用性的，调查过程中不断修正。爆发调查中的干预主要是实用性的，因为情况紧急，以及由于伦理的原因也不太可能设对照，所因为情况紧急，以及由于伦理的原因也不太可能设对照，所以研究性往往不强。以研究性往往不强。回忆：平均潜伏期（X）(M2M0)

3、(M0M1)/(M2M0)(M0M1)M1：病例数所占总数比例16时点；M0：50时点；M2：84时点、暴露日期M0X 19961997Age group(years)GenderTOTALMaleFemale0-92(17%)*2(8%)4(11%)10-192(17%)3(12%)5(13%)20-393(25%)9(35%)12(32%)40-592(17%)8(31%)10(26%)60+3(25%)4(15%)7(18%)TOTAL12(101%)26(101%)38(100%)*percentages refer to column totals.Of the initial 38

4、 persons who met the case definition,26(68%)were female with a median age of 31 years.Table 1.Age group and gender distribution for persons with E.coli O157:H7 infection(with PFGE pattern),Michigan,June 15-July 15,1997.(N=38)APPENDIX 1Age group(years)GenderTOTALMaleFemale0-15(3%)5(3%)10(3%)1-977(48%

5、)77(43%)154(45%)10-1936(22%)18(10%)54(16%)20-2910(6%)20(11%)30(9%)30-396(4%)12(7%)18(5%)40-497(4%)5(3%)12(4%)50-597(4%)17(10%)24(7%)60+14(9%)24(13%)38(11%)TOTAL162(100%)178(100%)340(100%)Age group(years)GenderTOTALMaleFemale0-92(17%)*2(8%)4(11%)10-192(17%)3(12%)5(13%)20-393(25%)9(35%)12(32%)40-592(1

6、7%)8(31%)10(26%)60+3(25%)4(15%)7(18%)TOTAL12(101%)26(101%)38(100%).MI CasesFoodNet DataThe 38 cases of E.coli O157:H7 infection meeting the investigation case definition were reported from 10 counties in the lower peninsula of Michigan.Figure 3.Date of illness onset for persons with E.coli O157:H7 i

7、nfection and the outbreak PFGE pattern,MI,June 15-July 15,1997.(N=38)Propagated source:single exposure,no secondary cases(e.g.,measles)Propagated source:secondary and tertiary cases(e.g.,hepatitis A)Common source:point exposure(e.g.,salmonella)Common source:Intermittent exposure(e.g.,contaminated bl

8、ood product)Figure 3.Date of illness onset for persons with E.coli O157:H7 infection and the outbreak PFGE pattern,MI,June 15-July 15,1997.(N=38)PeakOne incubation period Rubella=18 daysProbable time of exposureMaximum incubation 21 daysMinimum incubation 14 daysProbable time of exposureFigure 3.Ave

9、rage incubation period=4 days(range 3-8 days)Variable Cases(n=27)Controls(n=54)Female 18(67%)36(67%)Med Age 31 31 Rec water exposure 9(33%)21(39%)Other Ill person 6 (22%)9(17%)Day care 16(59%)33(61%)Farm 2(7%)2(4%)Fair 12(44%)24(44%)Travel 8 (30%)13(24%)Hamburger 17(63%)36(67%)Meat 14(52%)26(48%)Milk 21(78%)44(81%)Alfalfa sprouts 15(56%)4(7%)Lettuce 18(67%)34(62%)