Bay of Bengal found to be the source of global cholera pandemic

A recent study has determined that the Bay of Bengal was the source of a global cholera pandemic that has spread to Asia, Europe and the Americas over the past 60 years.

A team of scientists from the Sanger Institute at Cambridge University said that the disease has migrated via long-haul flights and have demonstrated that the infection is evolving into a more antibiotic-resistant form, according to the BBC.

In the study, which appears in the journal Nature, the researchers analyzed the genome of 154 cholera samples taken from around the world. Genome sequencing technology has improved in the last few years, making such an extensive study possible. Until recently, it is more likely that only four or five samples would have been used.

Similarities in the samples demonstrated how the bacteria are related to one another, while subtle differences between them show how they are evolving.

"We were surprised to see that the pattern we see is very clear," Dr. Nick Thomson of the Sanger Institute said, the BBC report. "All of the samples were related. There is a single global source of cholera in the Bay of Bengal."

It remains unclear why the Bay of Bengal is at the center of the pandemic, though the local ecology, climate and presence of river deltas are likely factors as to why it thrives there.

The study shows cases of cholera jumping quickly from continent to continent, suggesting that it was possibly spread by passengers on long flights.

"I think that's the only possible explanation. Our data show that this has happened, for example from Angola to South America. Many people can have cholera with no symptoms, so they transmit it without realizing,” Thomson said, according to the BBC.

Three waves of cholera have emerged from the Bay of Bengal since the 1950s. Since the second wave began, all of the strains have been shown to be antibiotic resistant, a worrying development. The resistance must have been acquired within 15 years of the first use of tetracycline and furazolidone to treat the disease.

"I'm not surprised it happened so fast," Thomson said, the BBC reports. "We think that antibiotic resistance moves between strains, and in one fell swoop a strain can become multi-resistant.”