SWIMMERS are being urged to take extra care in waters off Queensland amid warnings the deadly irukandji jellyfish is moving further south.

Four people have been hospitalised since Wednesday after suffering suspected irukandji stings off Queensland’s Fraser Coast.

The irukandji - the world’s smallest and most venomous box jellyfish - is usually found in waters north of Mackay, about 700km further up the coast.

James Cook University Associate Professor Jamie Seymour said it was clear the species was following warming sea temperatures south.

“We’ve got good data now that shows quite nicely that irukandji has been spreading down the east coast of Australia, moving slowly but surely southwards,” he told ABC radio.

“It’s only a matter of time before they get to the southern end of Fraser Island down to the Sunny Coast.”

Queensland Ambulance supervisor Martin Kelly said at least one of the cases off the Fraser Coast had been positively identified as an irukandji sting.

He said while it was enticing to swim in areas off the Queensland coast, it could also be quite dangerous.

“People can wear stinger suits but ... where you have a choice of not swimming in an environment where they (stingers) are you should do that or stay in the very shallow water,” he said.

“Prevention is far, far better than a cure.” Irukandji jellyfish are typically difficult to see as they are only roughly a cubic centimetre in size.

Their stings can cause very high blood pressure or affect the heart, potentially resulting in death.

They can also cause severe muscular pain, anxious behaviour, headaches and vomiting.

Stings should be doused in copious amounts of vinegar or seawater until medical help arrives, Mr Kelly said.