Four synchronous epidemics of measles and scarlet fever are observed in the historical data collected by colonial authorities in Victoria, Australia from 1853 to 1876, suggesting some sort of synergistic relationship between the two diseases. While epidemics of measles, as recorded by the colonial record keepers, still occurred during the remainder of the study period (until 1916), no further epidemics of scarlet fever occurred after 1876. This is suggestive of a change in Victoria’s disease ecology in the late 1870s. After analysis of the historical data for potential artifactual cases, it does not appear to be the result of confusion in diagnosis and changes in case definitions do not appear to have affected reporting of the causes of death. We conclude that the most likely explanation for the observed pattern is an epidemic synergy that ended after the 1876 epidemic. We hypothesize that this synergistic relationship between measles and scarlet fever in mid-nineteenth-century Victoria ended due to a shift in the dominant group A streptococci (GAS) M-type or the loss of a GAS bacteriophage. Support for this hypothesis comes from observations that other diagnoses associated with group A strep infections also changed their mortality profiles during the 1870s, particularly “Bright’s disease,” a possible descriptor of post-streptococcal glomerulonephritis. We situate the emergence and end of this pattern within the demographic and socioeconomic conditions of the Victorian gold-mining boom in the 1850s to 1870s and postboom changes in fertility, mortality, and housing infrastructure, highlighting the importance of social conditions in disease evolution.

中文翻译：

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1853-1916 年，澳大利亚维多利亚州的麻疹和猩红热流行病协同作用和不断演变的致病毒力

1853年至1876年澳大利亚维多利亚殖民当局收集的历史数据中观察到麻疹和猩红热的四次同步流行，表明这两种疾病之间存在某种协同关系。虽然根据殖民地记录员的记录，麻疹的流行在研究期间的剩余时间（直到 1916 年）仍然发生，但在 1876 年之后没有进一步的猩红热流行。这表明维多利亚的疾病生态在晚期发生了变化1870 年代。在分析了潜在人为病例的历史数据后，这似乎不是诊断混淆的结果，病例定义的变化似乎也没有影响死因的报告。我们得出结论，对观察到的模式最可能的解释是在 1876 年流行病之后结束的流行病协同作用。我们假设 19 世纪中叶维多利亚州麻疹和猩红热之间的这种协同关系由于主要 A 组链球菌 (GAS) M 型的转变或 GAS 噬菌体的丢失而结束。对这一假设的支持来自观察到与 A 组链球菌感染相关的其他诊断也改变了他们在 1870 年代的死亡率概况，特别是“布莱特病”，可能是链球菌感染后肾小球肾炎的描述。我们将这种模式的出现和结束置于 1850 年代至 1870 年代维多利亚时期金矿开采繁荣的人口和社会经济条件以及繁荣后生育率、死亡率和住房基础设施的变化中，