An aggressive species of marine bacteria responsible for many more deaths than sharks worldwide each year has been found in Sydney Harbour, with experts predicting outbreaks in spots along the city’s waterfront as water temperatures rise with global warming. 

Vibrio bacteria, which includes the species that causes cholera, can cause serious illness in humans and animals, including gastrointestinal sickness through consumption of contaminated seafood and flesh-eating infections in swimmers.

According to a new study by University of Technology Sydney scientists, two species of potentially dangerous Vibrio bacteria were detectable in particularly high concentrations when the water was warmest and in areas of mid-salinity, around Parramatta Park, Olympic Park and Rozelle.   

In the report, published in Frontiers of Microbiology on Tuesday, UTS researchers detail the composition of water samples collected from Sydney Harbour between Parramatta Park and Chowder Bay. 

While the cholera-causing strain of Vibrio cholerae was not found in any of the samples, a closely related strain of this species was detected in high quantities. It can cause skin infections and gastrointestinal infections if ingested or exposed to open wounds.

A second pathogen, Vibrio vulnificus, was also detected. It is responsible for 95 per cent of all seafood-related deaths in the US, and aggressive flesh-eating infections in swimmers, where it carries a mortality rate of up to 50 per cent amongst those infected, the report states.  

A spokesperson for the Department of Health said swimming in water always carries the risk of infection. 

“Germs, including a large range of bacteria and viruses, occur naturally and are very common in the environment. Vibrio species are commonly found in aquatic environments. Many of these bacteria and viruses are harmless to people. However some can be harmful if swallowed or if they infect wounds.”

Simple precautions include “not getting water in your mouth, keeping any wounds covered with a watertight dressing and avoiding injuries on sharp objects.”

Food and water safety is never simple.