Investigators at Massachusetts General Hospital (MGH) along with collaborators at the Sanger Institute in the U.K. and Dhaka Hospital of International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b) have, for the first time, analyzed numerous cholera strains in Dhaka, Bangladesh, where the disease is hyper-endemic to the population. Published in the June 25th issue of the journal Nature Genetics, the study found that multiple strains of cholera exist simultaneously in Dhaka and frequently, one individual may have several at a given time which may lead to genetic transfers and the formation of new strains.

“Our findings suggest that cholera maintains a very complex eco-system within and among humans in this hyper-endemic area,” says Edward T. Ryan, MD, director of global infectious disease at MGH and a co-author of the study. “A given strain can massively explode when optimal conditions come into existence, giving rise to new sub-strains that are constantly evolving and awaiting the next explosive expansion, and facilitating new epidemics in other at-risk communities such as Haiti and Africa.

By genetically sequencing samples collected from cholera patients at Dhaka Hospital from 2002 to 2005, investigators were able to trace all strains back to a common ancestor dated to approximately 1989 immediately following massive floods in Bangladesh and a large cholera epidemic involving more than 1 million people.

“New data shows that recent cholera outbreaks in Africa and the Western Hemisphere resulted from repetitive importation from South Asia,” says Ryan. “This means that any meaningful control strategy will require the elimination of the disease at its source which is why understanding how it survives and circulates is so critical.”

A full release for the study, which was supported by the National Institutes of Health and the Welcome Trust, can be found online at the Sanger Institute.

Massachusetts General Hospital, founded in 1811, is the original and largest teaching hospital of Harvard Medical School. The MGH Research Institute conducts the largest hospital-based research program in the nation, with an annual research budget of more than $900 million and major research centers in HIV/AIDS, cardiovascular research, cancer, computational and integrative biology, cutaneous biology, genomic medicine, medical imaging, neurodegenerative disorders, regenerative medicine, reproductive biology, systems biology, photomedicine and transplantation biology. The MGH topped the 2015 Nature Index list of health care organizations publishing in leading scientific journals and earned the prestigious 2015 Foster G. McGaw Prize for Excellence in Community Service. In August 2017 the MGH was once again named to the Honor Roll in the U.S. News & World Report list of "America's Best Hospitals."