Recommendable!
"... found that in the Ganges Delta, cholera bacteria rapidly gain and lose special armour that protects against attacks from the virus, known as bacteriophage ICP1.
The new research ... highlighted that maintaining these anti-viral defences leads to lower disease severity of cholera in humans and reduced ability to spread outside the country for this bacterial strain. ...
By looking at the ecology of cholera in South Asia, this study challenges the long-held belief that the Ganges Delta is the global source of cholera. Knowing more about the strains and the factors that influence the spread of cholera bacteria in different regions could help provide an early warning system, identifying high-risk strains before they escalate and allowing for early intervention. ...
Globally, we are in the seventh cholera pandemic, which started in 1961, with an estimated 1.3 to 4 million cases and up to 143,000 deaths per year from the condition worldwide. It has been shown that the seventh pandemic is caused by V. cholerae strain 7PET O1, originating from the Bay of Bengal, which borders Bangladesh and India, and it was thought that the Ganges Delta was the global source of cholera.
This new research sequenced bacterial samples from across Bangladesh and North India, creating the most comprehensive dataset of cholera in this area to date, containing over 2,300 genomes collected across approximately 20 years. They found that it was the Ganges Basin, not the Ganges Delta, that was the primary global source of cholera in that time.
By tracking the bacterial spread, they also uncovered that the bacteria do not simply follow the flow of rivers. Instead, they tend to stay within national borders, suggesting that human travel and population density are more important for cholera transmission than the natural environment.
They also found V. cholerae in Bangladesh, strain 7PET O1, rapidly gain and lose genetic elements known as defence systems, which act like armour helping them survive against their viral nemesis, the bacteriophage ICP1. ..."
From the abstract:
"The seventh pandemic of cholera, caused by the seventh pandemic El Tor lineage of Vibrio cholerae, was previously shown to have emanated in three global waves from the Bay of Bengal, bordering Bangladesh and India.
However, the respective roles of the Ganges Delta and Basin regions in seeding these global pandemic waves were not known.
Here we show that, although transmission events occur between Bangladesh and India, V. cholerae in the two countries has largely evolved separately over the past 20 years, apparently constrained by national borders rather than by hydrological features, such as the Ganges Delta and Basin.
Evolution within Bangladesh was distinct from that seen in India, involving rapid gain and loss of genes and mobile genetic elements, particularly those involved in phage defence. The loss of these systems was associated with increased risk of severe disease and transmission outside Bangladesh.
Lineage replacement in Bangladesh in 2018, resulting in a major change in phage defence systems, was accompanied by a rapid change in the lineage and anti-defence system of lytic phage ICP1.
Here we show that the Ganges Basin, falling across Bangladesh and Northern India, rather than the Ganges Delta, probably acts as a global launch pad for pandemic disease. This shifts our understanding of Bangladesh as the purported global source of cholera and underscores the potential role of phage in controlling spread of lineages within the current seventh pandemic."
Evolution of pandemic cholera at its global source (open access)
Fig. 1: Dynamics of V. cholerae sublineages in Bangladesh and their genetic profiles over time.
