Shigellosis, the bowel infection that results from shigella exposure, can result in vomiting, stomach cramps, diarrhoea, fever and nausea. Symptoms can appear between 12 hours and four days after exposure, and can last between four and seven days. It is estimated to cause 190 million cases of diarrhoea globally a year.

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Researchers are not yet sure what is behind the outbreak, but they suspect it may be linked to a rise in casual sex through online dating and reduced fear of contracting HIV due to the increase in people taking pre-exposure prophylaxis medication known as PrEP. A jump in global travel is also thought to be linked to the surge.

"We know that the incidence of shigella has gone up, not just in Victoria, but across Australia over the past 10 years and it is a major public health concern," lead researcher and University of Melbourne Professor, Deborah Williamson, said.

"These things can seemingly emerge from nowhere and spread very rapidly. One of the most concerning aspects of our data is that 80 or so years ago we saw just a tiny handful of these very drug resistant cases and now it is becoming one of the more dominant strains of shigella."