New research published in the journal PLOS Neglected Tropical Diseases suggests that an El Niño event may have played a role in aiding the establishment and spread of a novel cholera strain during an early 20th-century pandemic. The study, conducted by Xavier Rodo of Instituto de Salud Global de Barcelona, Spain, and his colleagues, supports the idea that climate anomalies could create opportunities for the emergence of new cholera strains. This is particularly relevant given that the ongoing cholera pandemic, which began in 1961, has claimed the lives of over 1 million people worldwide.
The drivers of past cholera pandemics have been a subject of uncertainty, but one hypothesis posits that anomalous climate conditions may work in conjunction with genetic changes of Vibrio cholerae to facilitate the spread and dominance of new strains. To investigate this further, Rodo and his team examined historical records of climate conditions and cholera deaths in various regions of former British India during the sixth cholera pandemic, which lasted from 1899 to 1923. By using statistical and computational tools, they were able to compare past conditions with climate and cholera data from the ongoing pandemic.
The analysis revealed that abnormal patterns of cholera deaths from 1904 to 1907 coincided with unusual seasonal temperatures and rainfall levels associated with an El Niño event. This timing correlated with the establishment of a new invasive strain during the sixth pandemic. Furthermore, the historical climate conditions bore similarities to strong El Niño events that have been linked to cholera strain changes in the current pandemic. These findings provide evidence that anomalous climate events could potentially aid in the establishment and spread of new cholera strains.
Looking ahead, the researchers utilized climate prediction models to explore future possibilities for climate-facilitated emergence of new cholera strains. They discovered that climate change-driven increases in climate variability and extremes could heighten the chances of novel strains emerging through the end of the current century. In light of these findings, the scientists emphasize the need for additional research that focuses on the interaction between cholera evolution and climate anomalies to deepen the understanding of this deadly disease and its potential impacts on public health.
Dr. Rodó and Dr. Mercedes Pascual, a co-author of the study, highlight the importance of considering both climate conditions and pathogen evolution as key drivers of major epidemics and pandemics. They note that these two factors are often studied separately but can come together synergistically to underlie the establishment and widespread transmission of new strains. Their research provides indirect evidence of the combined impact of climate anomalies and pathogen evolution on the emergence of unusually large outbreaks, underscoring the need for integrated approaches to studying and addressing infectious diseases like cholera.