Rodó Xavier, Bouma Menno Jan, Rodríguez-Arias Miquel-Àngel, Roy Manojit, De Yebra Pau, Petrova Desislava, García-Díez Markel, Pascual Mercedes
ICREA, Barcelona, Spain.
CLIMA (Climate & Health) Group, ISGlobal, Barcelona, Spain.
PLoS Negl Trop Dis. 2024 Aug 1;18(8):e0012275. doi: 10.1371/journal.pntd.0012275. eCollection 2024 Aug.
Explanations for the genesis and propagation of cholera pandemics since 1817 have remained elusive. Evolutionary pathogen change is presumed to have been a dominant factor behind the 7th "El Tor" pandemic, but little is known to support this hypothesis for preceding pandemics. The role of anomalous climate in facilitating strain replacements has never been assessed. The question is of relevance to guide the understanding of infectious disease emergence today and in the context of climate change.
METHODOLOGY/PRINCIPAL FINDINGS: We investigate the roles of climate and putative strain variation for the 6th cholera pandemic (1899-1923) using newly assembled historical records for climate variables and cholera deaths in provinces of former British India. We compare this historical pandemic with the 7th (El Tor) one and with the temporary emergence of the O139 strain in Bangladesh and globally. With statistical methods for nonlinear time series analysis, we examine the regional synchrony of outbreaks and associations of the disease with regional temperature and rainfall, and with the El Niño Southern Oscillation (ENSO). To establish future expectations and evaluate climate anomalies accompanying historical strain replacements, climate projections are generated with multi-model climate simulations for different 50-year periods. The 6th cholera pandemic featured the striking synchronisation of cholera outbreaks over Bengal during the El Niño event of 1904-07, following the invasion of the Bombay Presidency with a delay of a few years. Accompanying anomalous weather conditions are similar to those related to ENSO during strain replacements and pandemic expansions into Africa and South America in the late 20th century. Rainfall anomalies of 1904-05 at the beginning of the large cholera anomaly fall in the 99th percentile of simulated changes for the regional climate.
CONCLUSIONS/SIGNIFICANCE: Evolutionary pathogen change can act synergistically with climatic conditions in the emergence and propagation of cholera strains. Increased climate variability and extremes under global warming provide windows of opportunity for emerging pathogens.
自1817年以来，霍乱大流行的起源和传播原因一直难以捉摸。进化病原体变化被认为是第七次“埃尔托”大流行背后的主要因素，但对于之前的大流行，几乎没有证据支持这一假设。异常气候在促进菌株替代方面的作用从未得到评估。这个问题对于理解当今和气候变化背景下传染病的出现具有重要意义。
方法/主要发现：我们利用新收集的关于前英属印度各省气候变量和霍乱死亡的历史记录，研究气候和假定的菌株变异在第六次霍乱大流行（1899 - 1923年）中的作用。我们将这次历史大流行与第七次（埃尔托）大流行以及孟加拉国和全球范围内O139菌株的短暂出现进行比较。通过非线性时间序列分析的统计方法，我们研究了疫情的区域同步性以及该疾病与区域温度、降雨量和厄尔尼诺 - 南方涛动（ENSO）的关联。为了建立未来预期并评估伴随历史菌株替代的气候异常，我们使用多模型气候模拟针对不同的50年时间段生成了气候预测。第六次霍乱大流行的特点是，在1904 - 1907年的厄尔尼诺事件期间，孟加拉的霍乱疫情惊人地同步，此前孟买管辖区已被入侵数年。伴随的异常天气状况与20世纪后期菌株替代以及大流行扩展到非洲和南美洲期间与ENSO相关的状况相似。在霍乱大异常开始时的1904 - 1905年降雨异常处于区域气候模拟变化的第99百分位。
结论/意义：进化病原体变化在霍乱菌株的出现和传播中可与气候条件协同作用。全球变暖下增加的气候变异性和极端事件为新兴病原体提供了机会窗口。
