Recent research indicates that an El NiƱo event likely played a role in the emergence and propagation of a new cholera strain during an early 20th-century pandemic. This finding bolsters the concept that climate irregularities might provide a conducive environment for the appearance of new cholera strains. Xavier Rodo and his team from the Instituto de Salud Global de Barcelona, Spain, share these insights in the open-access journal PLOS Neglected Tropical Diseases.
Since 1961, over a million individuals around the globe have succumbed to an ongoing cholera pandemic, marking the seventh cholera outbreak since 1817. The factors behind previous cholera pandemics remain unclear. However, one theory suggests that unusual climate conditions might work alongside genetic shifts in Vibrio choleraeāthe bacterium responsible for the diseaseāthereby encouraging the spread and prevalence of new strains.
To investigate the potential connection between climate and cholera, Rodo and his colleagues employed a variety of statistical and computational techniques to analyze historical climate data and cholera mortality records from different regions of former British India during the sixth cholera pandemic, which spanned from 1899 to 1923. They also compared these historical patterns with current data from the ongoing pandemic.
Their analysis uncovered that unusual patterns of cholera deaths between 1904 and 1907 coincided with atypical seasonal weather and rainfall patterns linked to an El NiƱo event. This timing corresponds with the emergence of a new invasive strain during the sixth pandemic period. Furthermore, the historical climate conditions mirrored strong El NiƱo episodes connected to changes in cholera strains during the ongoing pandemic.
These observations support the hypothesis that abnormal climate events could facilitate the emergence and distribution of new cholera strains.
The researchers proceeded to evaluate future possibilities regarding climate-driven emergence of new cholera strains using standard climate models. They discovered that climate change, leading to increased climate variability and extremes, might elevate the chances of new strain emergence as we approach the end of this century.
In light of these findings, the scientists advocate for further exploration of the relationship between cholera evolution and climate anomalies to better understand this deadly disease.
Dr. Rodo and co-author Dr. Mercedes Pascual state, “Changes in climate conditions or the evolutionary shifts of a pathogen can significantly drive major epidemics and pandemics. Yet, these two factors are often examined separately when analyzing the cause of severe outbreaksā¦ Our study provides indirect evidence that they can work together synergistically to promote the establishment and widespread transmission of new strains.”
