Department of Environmental Sciences, University of Virginia, Charlottesville, Virginia, United States of America.
PLoS One. 2012;7(3):e34091. doi: 10.1371/journal.pone.0034091. Epub 2012 Mar 28.
The substantial winter influenza peak in temperate climates has lead to the hypothesis that cold and/or dry air is a causal factor in influenza variability. We examined the relationship between cold and/or dry air and daily influenza and pneumonia mortality in the cold season in the New York metropolitan area from 1975-2002. We conducted a retrospective study relating daily pneumonia and influenza mortality for New York City and surroundings from 1975-2002 to daily air temperature, dew point temperature (a measure of atmospheric humidity), and daily air mass type. We identified high mortality days and periods and employed temporal smoothers and lags to account for the latency period and the time between infection and death. Unpaired t-tests were used to compare high mortality events to non-events and nonparametric bootstrapped regression analysis was used to examine the characteristics of longer mortality episodes. We found a statistically significant (p = 0.003) association between periods of low dew point temperature and above normal pneumonia and influenza mortality 17 days later. The duration (r = -0.61) and severity (r = -0.56) of high mortality episodes was inversely correlated with morning dew point temperature prior to and during the episodes. Weeks in which moist polar air masses were common (air masses characterized by low dew point temperatures) were likewise followed by above normal mortality 17 days later (p = 0.019). This research supports the contention that cold, dry air may be related to influenza mortality and suggests that warning systems could provide enough lead time to be effective in mitigating the effects.
温带地区冬季流感高发，这导致了一个假设，即寒冷和/或干燥的空气是流感变异的一个因果因素。我们研究了寒冷季节纽约大都市区 1975-2002 年期间寒冷和/或干燥空气与每日流感和肺炎死亡率之间的关系。我们进行了一项回顾性研究，将纽约市及其周边地区 1975-2002 年的每日肺炎和流感死亡率与每日气温、露点温度（衡量大气湿度的指标）和每日大气团类型联系起来。我们确定了高死亡率日和时期，并采用时间平滑器和滞后来解释潜伏期和感染与死亡之间的时间间隔。未配对的 t 检验用于比较高死亡率事件与非事件，非参数引导回归分析用于检查较长死亡率事件的特征。我们发现，露点温度低的时期与 17 天后高于正常的肺炎和流感死亡率之间存在统计学上显著的关联（p=0.003）。高死亡率事件的持续时间（r=-0.61）和严重程度（r=-0.56）与事件发生前和期间的早晨露点温度呈负相关。潮湿极地气团常见的周（露点温度低的气团特征）也会导致 17 天后的死亡率高于正常（p=0.019）。这项研究支持寒冷、干燥的空气可能与流感死亡率有关的观点，并表明预警系统可以提供足够的提前期，以有效地减轻其影响。
