SYDNEY, April 13 -- When swimming in Australia's most famous harbour, take caution as there could be a pathogenic marine bacteria around you which causes more deaths each year than sharks, the nation's scientists warned on Wednesday.

High concentrations of two Vibrio bacteria species have been found in the warmest parts of Sydney harbour, one of the Australia's most densely populated and heavily used waterways, and also in less salty areas deeper inside the estuary.

Though the Vibrio bacteria causes cholera, the strain found in Sydney Harbour instead causes gastrointestinal illness through the consumption of contaminated seafood as well as flesh eating infections in swimmers with open wounds.

"This pathogen is responsible for 95 percent of all seafood-related deaths in the United States and carries a high mortality rate of approximately 50 percent in infected individuals," University of Technology microbiologist Dr. Maurizio Labbate said in a statement on Wednesday.

The findings, published in the scientific journal Frontiers in Microbiology, add to the understanding around the occurrence and distribution of the pathogenic bacteria, with the"perfect storm"scenario for outbreaks occurring in warm, less saline waterways.

This understanding is essential as more and more Vibrio-related infections increase in coastal ecosystems worldwide, particularly in ecosystems under environmental stress and water temperatures warm from human-induced climate change.

"Given the potential for these species to cause serious illness in humans as well as disease in a wide range of marine organisms including fish, corals and oysters, understanding when, where and why outbreaks of pathogenic Vibrios will occur is essential for public and ecosystem health management," said chief investigator and UTS Associate Professor of microbial ecology Justin Seymour.