Another child has been flown to Hervey Bay Hospital with a suspected Irukandji sting after swimming in a creek off Wathumba Road on K'gari (Fraser Island) in Queensland on Wednesday afternoon.
It follows three young girls who had been swimming at the same site being flown to hospital on Tuesday, also with suspected Irukandji stings.
The ABC understands the girls have since been released from hospital.
Following the incidents, a toxicologist is calling for more research into venomous jellyfish, warning that beaches may be forced to close in the future if the movement of marine stingers changes over time.
Toxicologist and James Cook University associate professor Jamie Seymour said it was "not unusual" to have severe stingers at K'gari (Fraser Island).
"We've seen over the last 15–20 years the number of stings from Fraser Island increase," Dr Seymour said.
"We certainly found Irukandji jellyfish down there probably 15 years ago."
The 2019 season was particularly bad for jellyfish stings in Queensland, with 19 people taken to hospital with suspected Irukandji stings.
The Queensland Ambulance Service (QAS) describes Irukandji as a small, extremely venomous species of box jellyfish.
The creature is approximately 2 centimetres in diameter, making them hard for swimmers to spot in the water.
Their stings can cause severe pain, vomiting, and breathing difficulties.
Unknown movements
Dr Seymour said more information about jellyfish was urgently needed, including their movements and physiology.
"Our biggest issue is that we know very little about these animals in areas like Fraser Island," he said.
"We don't know where they come from, we don't know the times of year they turn up and when they disappear.
"We've found one species of jellyfish down there that gives rise to Irukandji Syndrome.
"We know there's at least eight [species] in Australia."
Beach closures possible
Dr Seymour warned that if the number of severe stings increased, authorities may have to implement extreme measures.
"I can see very soon that the only option we're going to have is to stop people getting in the water," he said.
"[If] You end up with half a dozen of these animals on the beach, you have one option; that's to shut the beach.
"These animals are going to become more and more of a problem for a variety of reasons, but mainly because we've got more and more people getting in the water."
Queensland's Department of Environment and Science (DES) was contacted for comment.
Dr Seymour said a solution was needed that would "decrease the effect of people being stung".
"For Irukandji, we really need a handle on the entire east coast [and] west coast of Australia," he said.
"Anywhere north of probably Fraser Island for the east coast, and all the way down into Ningaloo on the west coast."
