影响上海地区冬春季流感流行强度的关键局地气象因子研究

A study of critical local weather factors affecting the intensity of influenza epidemics during winter and spring in Shanghai

识别影响流感流行强度的关键气象因子有助于提高流感疫情预警、预测能力。基于2010—2018年上海市冬、春季周流感样病例数(ILI)和气象观测资料,采用分布滞后非线性模型(DLNM)和广义相加回归模型(GAM)系统分析了ILI与多种气象因子的关联,在此基础上使用多元逐步回归模型识别调控流感流行强度的关键气象因子。结果表明,冬、春季平均气温和相对湿度与ILI呈反向关系,低温和低湿效应的滞后持续时间较长,5℃和50%环境下滞后3周的累积风险分别为2.16(95%CI:1.18—3.95)和2.51(95%CI:1.96—3.23),且气温与相对湿度对ILI存在交互影响,干燥环境会显著加强冷效应。此外,与气温有关的不稳定天气要素也与ILI具有显著关联,其中气温日较差对ILI的影响在当周最大,每升高1℃,ILI风险增加1.8%(95%CI:0.2%—3.4%),ILI流行早期的冷空气活动频次与ILI呈单调递增线性关系,冷空气活动频次每增加1次,ILI风险增大6.8%(95%CI:2.1%—11.7%)。其中,流行早期阶段的频繁冷空气活动和流行期内的干燥环境为严重流感事件的爆发提供了合适的外界环境。研究结果可为科学理解暖冬背景下出现的大规模流感流行事件提供理论依据。

Identifying critical weather factors that affect the intensity of influenza epidemics can promote early warning of influenza outbreak.Based on influenza-like illness(ILI)and meteorological observations during winter and spring in Shanghai from 2010 to 2018,a distributed lag non-linear model(DLNM)and generalized additive regression models(GAM)are used to investigate the relationship between ILI and various weather factors.Additionally,the multiple stepwise regression model is used to pinpoint significant weather factors affecting the intensity of influenza epidemics.Results indicate that there are negative correlations between ILI and temperature and relative humidity,and the relative risk(RR)of ILI increases as both factors decrease.The effects can persist until three weeks later and remain statistically significant,e.g.the cumulative RR of exposure to cold(5℃)and dry(50%)environments are up to 2.16(95%CI:1.18—3.95)and 2.51(95%CI:1.96—3.23),respectively.Meanwhile,there is also a significant interaction effect between relative humidity and temperature,with a dry environment significantly enhancing the cold impact.In addition,unstable weather elements related to air temperature are also significantly associated with ILI,with the risk rising by 1.8%(95%CI:0.2%—3.4%)for every 1℃increase.The frequency of cold air activity at the start of the epidemic and the peak ILI risk also feature a significant monotonically increasing linear relationship,with an increase risk of 6.8%(95%CI:2.1%—11.7%)for one more cold air process.Among these sensitive weather factors,frequent cold air activities and dry conditions may form an environment conducive for the outbreak of serious influenza epidemic.The findings provide a theoretical basis for scientific understanding of widespread influenza epidemics that occurred in warm winters.