The finding is important for studying the origin and spread of epidemics caused by the cholera bacterium, Vibrio cholerae.
Andrew Camilli at Tufts University School of Medicine in Boston, Massachusetts, USA, and colleagues compared V. cholerae bacteria from natural sources (the bacteria live in soil and fresh water) and those taken from human stool samples.
They found that human-derived bacteria are "hyper-infectious", and that they over-express genes required for obtaining nutrients and increasing motility.
|V. cholerae is 500-times more infectious after passing through human guts.
Furthermore, the bacteria remain hyper-infectious after being excreted into the environment by the host.
There are between 100,000 and 300,000 cases of cholera infection reported each year.
The infection causes acute diarrhea and vomiting, and 1 in 100 victims dies from dehydration.
Hosts may also prime other infectious bacteria, the authors say.