Grimstad P R, Barrett C L, Humphrey R L, Sinsko M J
Am J Epidemiol. 1984 Jun;119(6):913-30. doi: 10.1093/oxfordjournals.aje.a113814.
The vast under-reporting of La Crosse virus and St. Louis encephalitis virus infections in Indiana residents was evident when numerous inapparent infections were detected retrospectively using serum dilution neutralization analyses of serum obtained in November 1978-April 1979 from 10,208 persons (0.2% of the state's population). An antibody prevalence rate of 3.6% to St. Louis encephalitis virus was detected in the sample population as a whole, with rates as high as 13.2% for residents of individual counties. The estimated average annual rate of infection for the whole population was 0.32%. The antibody prevalence to La Crosse virus in the sample population as a whole was 2.3%, with rates ranging up to 12.5% for residents of individual counties. The estimated average annual rate of infection for the whole population was 0.29%. The epidemiologic behavior of the two viruses was quite different. Age-specific antibody prevalence for St. Louis encephalitis virus indicated a pattern of endemic infection existed in the population as a whole; antibody prevalence rose as the population aged. However, many other infections apparently occurred during the 1975 and earlier epidemics. Age-specific antibody prevalence for La Crosse virus indicated a typical pattern of endemic infection was present. The antibody prevalence to La Crosse virus was best described by the Poisson distribution and that of St. Louis encephalitis virus by the negative binomial distribution. These data support the hypothesis that St. Louis encephalitis virus primarily produces intermittent epidemics in the Midwest while La Crosse virus produces continuous seasonal endemic infections. However, evidence suggestive of a low level of interepidemic St. Louis encephalitis virus infection in the population was also obtained. Computer-drawn synagraphic mapping view "maps" of regional antibody prevalence rates demonstrated the existence of distinct foci of infection for each virus in the human population.
1978年11月至1979年4月期间，从10208人（占该州人口的0.2%）采集血清，通过血清稀释中和分析进行回顾性检测，发现众多隐性感染，这表明印第安纳州居民中拉克罗斯病毒和圣路易斯脑炎病毒感染的漏报情况极为严重。在整个样本人群中，检测到圣路易斯脑炎病毒抗体流行率为3.6%，个别县居民的流行率高达13.2%。整个人口的估计年平均感染率为0.32%。整个样本人群中拉克罗斯病毒抗体流行率为2.3%，个别县居民的流行率高达12.5%。整个人口的估计年平均感染率为0.29%。这两种病毒的流行病学行为差异很大。圣路易斯脑炎病毒的年龄特异性抗体流行率表明，整个人口中存在地方性感染模式；抗体流行率随人口年龄增长而上升。然而，在1975年及更早的疫情期间显然还发生了许多其他感染。拉克罗斯病毒的年龄特异性抗体流行率表明存在典型的地方性感染模式。拉克罗斯病毒的抗体流行率最好用泊松分布来描述，而圣路易斯脑炎病毒的抗体流行率则用负二项分布来描述。这些数据支持以下假设：圣路易斯脑炎病毒主要在中西部地区引发间歇性疫情，而拉克罗斯病毒则引发持续的季节性地方性感染。然而，也获得了表明人群中圣路易斯脑炎病毒存在低水平流行间期感染的证据。计算机绘制的区域抗体流行率的合成图“地图”显示，人群中每种病毒都存在明显的感染聚集区。
