Migration most likely source of cholera epidemic in Yemen

The most likely source of the cholera epidemic in Yemen has been discovered by scientists. Through the use of genomic sequencing, scientists at the Wellcome Sanger Institute and Institut Pasteur estimate the strain of cholera-causing the current outbreak in Yemen - the worst cholera outbreak in recorded history - came from Eastern Africa and entered Yemen with the migration of people in and out of the region.

The results, published on January 2 in Nature show that genomic data and technologies can enable researchers to estimate the risk of future cholera outbreaks in regions like Yemen and ultimately be used to better target interventions.

Yemen is facing the worst epidemic of cholera since records began. The disease has affected over 1 million people and caused almost 2,500 deaths.

The population in Yemen has experienced two outbreaks of cholera; the first occurred between September 2016 and April 2017, and the second began later in April 2017 and has since resulted in more than 1 million suspected cases.

To understand the nature of the strain of bacteria behind these devastating cholera outbreaks, researchers from the Wellcome Sanger Institute, Institut Pasteur and their collaborators sequenced the genomes of Vibrio cholerae from cholera samples collected in Yemen and nearby regions.

Researchers compared these genomic sequences to a global collection of over 1000 cholera samples from the current and ongoing pandemic, known as the seventh cholera pandemic.

Scientists discovered that the cholera strain causing the Yemen epidemic is related to a strain first seen in 2012 in South Asia that has spread globally, but the Yemeni strain did not arrive directly from South Asia or the Middle East. This particular cholera strain was circulating and causing outbreaks in Eastern Africa between 2013 and 2014, prior to appearing in Yemen in 2016.

Cholera is a diarrhoeal disease, transmitted through contaminated food and water, which is most prevalent in regions with poor sanitation. In Yemen, where there have been more than three years of conflict, around 16 million of the 29 million inhabitants have no access to safe water and basic sanitation.