Zhang Shun-xiang, Gu Li-niu, He Jian-fan, Cheng Xiao-wen, Hu Dong-sheng, Lü Xing, Wu Chun-li, Lu Jian-hua, Fang Shi-song
Shenzhen Center for Disease Control and Prevention, China.
Zhonghua Yu Fang Yi Xue Za Zhi. 2009 Oct;43(10):861-6.
To determine the epidemiological characteristics of seasonal influenza in Shenzhen from 2005 to 2007 and the molecular variation of HA1 domain of influenza H3N2 viruses.
The consultation rate for influenza-like illness (ILI) were calculated weekly for indicating the influenza activities (the Shenzhen Influenza Surveillance System mainly consisted of 16 institutions with 9 hospitals, 6 districts and one municipal centers of disease control and prevention). Pharyngeal swabs from the cases of ILI, which were collected during 2005 to 2007 from the city-wide and quality-controlled surveillance network, were used to propagate the viruses. The HA1 region of the influenza A/H3N2 viruses were detected by RT-PCR and sequenced subsequently. The analyses of pairwise amino acid variations, genetic clustering and phylogenetics was performed.
The activity levels of influenza showed certain changes during each year from 2005 to 2007, and there were summer peaks from May to July in 2006 and 2007. The positive rates of influenza virus were 4.78% (114/2385), 5.77% (212/3674) and 12.12% (343/2831) from 2005 to 2007 respectively. The weekly isolating rates changed accordingly with the trend of the percentages of ILI. The proportions of influenza H3N2 virus were 25.46% (28/114) and 2.83% (6/212) in 2005 and in 2006 respectively, but the proportion increased to 62.68% (215/343), which indicated that H3N2 virus became the predominant strain in 2007. Phylogenetic clustering analysis of influenza H3N2 virus revealed that there were 5 clades. The viruses which were isolated in 2005 contained in the clade I and II, the viruses in 2006 were comprised in clade III, and clade IV and V included the viruses isolated in 2007. Although the stem of cladogram developed with one accord of the time isolated viruses, the viruses which were similar to vaccine strains had circulated in Shenzhen before a given strain was determined as vaccine strain by WHO. It was also noticed that more amino acid changes at antigenic sites, especially at sites A and B in the H3N2 viruses, were found in 2007 than that in 2005 and in 2006. But the sequences at the receptor-binding sites and disulphide bond sites were conserved and no new circulating strain for genetic reassortment had been found in the period.
Shenzhen might be one of areas where the ongoing genetic drift of influenza H3N2 viruses appeared earlier in China. The changes of influenza H3N2 virus showed the active status in the population. The results suggested that monitoring seasonal influenza viruses by sequence analysis could provide important and timely information on the appearance of strains with epidemiologic significance.
确定2005年至2007年深圳季节性流感的流行病学特征以及H3N2流感病毒HA1结构域的分子变异情况。
每周计算流感样疾病（ILI）的咨询率以指示流感活动情况（深圳流感监测系统主要由16个机构组成，包括9家医院、6个区和1个市疾病预防控制中心）。2005年至2007年期间，从全市质量控制监测网络收集的ILI病例的咽拭子用于病毒培养。采用RT-PCR检测甲型H3N2流感病毒的HA1区域并随后进行测序。进行氨基酸差异、遗传聚类和系统发育分析。
2005年至2007年每年流感活动水平呈现一定变化，2006年和2007年5月至7月出现夏季高峰。2005年至2007年流感病毒阳性率分别为4.78%（114/2385）、5.77%（212/3674）和12.12%（343/2831）。每周分离率随ILI百分比趋势相应变化。2005年和2006年甲型H3N2流感病毒比例分别为25.46%（28/114）和2.83%（6/212），但2007年该比例增至62.68%（215/343），表明H3N2病毒在2007年成为优势毒株。甲型H3N2流感病毒的系统发育聚类分析显示有5个分支。2005年分离的病毒包含在分支I和II中，2006年的病毒包含在分支III中，分支IV和V包括2007年分离的病毒。尽管进化树主干与分离病毒的时间一致发展，但在世界卫生组织将某一毒株确定为疫苗株之前，与疫苗株相似的病毒已在深圳传播。还注意到，2007年H3N2病毒抗原位点尤其是A和B位点的氨基酸变化比2005年和2006年更多。但受体结合位点和二硫键位点的序列保守，在此期间未发现新的基因重配流行毒株。
深圳可能是中国H3N2流感病毒持续基因漂移出现较早的地区之一。H3N2流感病毒的变化显示其在人群中的活跃状态。结果表明，通过序列分析监测季节性流感病毒可为具有流行病学意义的毒株出现提供重要且及时的信息。
