广西输入性SARS病例传播因素的流行病学研究

EPIDEMIOLOGICAL INVESTIGATION IN THE SPREAD FACTORS OF IMPORTATION CASES OF SEVERE ACUTE RESPIRATORY SYNDROME IN GUANGXI

目的:为了明确输入性SARS病例在广西引起易感人群传染的危险性以及影响病毒传播的危险因素,为预防SARS在广西的再度流行提供科学依据。方法:①应用回顾性研究和随访研究的流行病学方法收集2003年在广西发生的两个疫点中的输入性和继发性SARS病例资料,应用描述流行病学方法描述每个输入性病例引起继发性病例传播的传播链。②通过对输入性SARS病例到继发性病例的发生的流行病学调查资料和传播链的分析,找出影响输入性病例传播的危险因素。③应用血清流行病学方法,于2003年5月及2005年11月分别两次对此两疫点发生的输入性、继发性SARS病例、家庭成员及密切接触者、参与诊治的医护人员进行血清流行病学调查。应用ELISA法检测研究对象血清中的SARS冠状病毒抗体IgG和IgM。结果:参与诊治先证A诊治的全部医护人员的继发性隐性感染率为2·1%(2/97),显著低于参与先证A护理的亲属的继发性发病率41·7%(5/12)(P<0·01)。参与先证A1护理的亲属9人中,有5人属于继发性隐性感染,继发性感染率为55·6%(5/9),远高于医护人员的继发性感染率4%(3/75)(P<0·01)。结论:输入性SARS病例如果IgM、IgG双抗体阳性者病毒的传染力极强,第2代病例可能由于病毒的变异而导致毒力下降。广西输入性病例引起第2代病例的感染主要原因是通风不良、近距离无防护密切接触;通风良好可以降低空气中的病毒浓度,即使出现感染,也仅引起隐性感染;气候是影响SARS的流行重要因素之一。

Objective.To make clear the spread situation of Severe Acute Respiratory Syndrome （SARS） in susceptible persons and the factors influencing the importation cases of SARS spread so as to prevent again SARS spread in Guangxi. Methods. ①Epidemiological respective study and visiting methods were used to collect the data of the area of the two importation cases （case A and case A1）, and of the secondary cases of SARS that confirmed in Guangxi 2003 as well. ②To find out the factors affecting the spread of importation SARS, the epidemiological survey data and spreading chain was investigated. ③With serological epidemiology survey, antibody IgG and IgM of SARS in the subjects, the importation and the secondary cases as well as the persons who contacted with the importation cases directly or indirectly, were tested with ELISA method. Result：The covert infection rate （2.1% （2/97） in medical workers who provided medical care for the forerunner case A was significantly lower than the rate 41.7%（5/12） of the secondary overt infection in patient＇s acquainted persons who had looked after the importation case A （ P〈0.01）. The infection rate 55.6%（5/9） （including covert and overt infection） in acquainted persons who attended to the importation case A1 was also remarkable higher than the secondary infection rate 4% （3/75） in medical workers who had offered medical care for the importation case A1 （ P〈0.01）. Conclusion. The investigation results suggest that the infectivity of the importation cases is higher in the patients who have two antibodies positive, IgG and IgM of SARS, and with lower infectivity in the secondary cases for the virus variation. The main dangerous factors of the importation SARS spread in susceptible persons in Guangxi relates to the crowded and poorly ventilating air condition at home and the contacted patients without personal protective measures. With good air ventilation, the concentration of virus in the air may be diluted and cause just only covert infection; the climate is one of the important factors in the prevalence of SARS in Guangxi.