上海市1999～2003年流行性感冒流行特征分析

Analysis on epidemic characterization of influenza in Shanghai from 1999 to 2003

目的了解上海市流感流行特征,探讨流感病毒优势株的变化,为流感防制提供科学依据。方法选择流感监测点,采用流行病学、病原学和血清学方法进行调查。结果1999年流感样病例春秋两季高峰明显,2000年以来季节发病高峰减弱。流感病毒优势株为B型和H1N1型,分别占总病毒分离数的62.81%和32.23%,H3N2亚型活动弱,仅4.96%。1999年主要流行株为B型,2000年为H1N1亚型,2001年以来H1N1亚型和B型交替成为优势株。H1N1亚型病毒抗原性存在某些变异,B型病毒抗原性未发生变异。一般人群流感抗体水平保持较高水平,H3N2、H1N1和B型几何平均滴度(GMT)分别为70.00,67.33和87.67,但小年龄和老年龄组的抗体水平低于成年人。结论上海市近5年流感发病高峰减弱,以B型和H1N1亚型为优势株,其抗原性末发生明显的变异。与我国北方等省H3N2亚型为优势株不同。小年龄和老年人为易感人群。需加强H3N2亚型流感病毒监测,注意H3N2亚型病毒变异引起流行的可能性。

Objective To study the epidemic characterization of influenza in Shanghai, and to discuss the changes of the predominant strains of influenza in order to provide scientific basis for the prevention of influenza.Methods Surveillance sites were selected and the investigation was carried out by the methods of epidemiology, pathology and serology.Results There were two apparent seasonal peaks in 1999, but the trend was weakened since 2000. The predominant strains of influenza were B type and influenza A subtype H1N1 with the rate of isolation 62.81% and 32.23% respectively,and they are both prior to influenza A subtype H3N2 whose rate was 4.96%. The main predominant strain were B type in 1999, and influenza A subtype H1N1 in 2000. Since 2001,the strains were both co-circulating. It seemed that variations had occurred in the antigenicity of infiuenza A subtype H1N1,but nor did B type. The antibody in general public remained at a comparatively high level. The GMT of H3N2, H1N1 and B were 70.00, 67.33, 87.67 respectively. The antibody levels in the groups below 5 years old and beyond 60 years old were lower than those in the other groups. Conclusion The incidence peak of inrtuenza had declined during these 5 years in Shanghai. Unlike influenza A subtype H3N2 as the predominant strain of the northern China, B type and influenza A subtype H1N1 were the main predominant strains in Shanghai. There weren't obvious changes of antigenicity. The younger and the older were vulnerable populations. It was necessary to strengthen the surveillance of influenza A subtype H3N2, especially to concern the possibility of epidemic due to the variation of influenza A subtype H3N2.