Three weeks after her Tokyo Paralympics silver medal, Parker finished the half-Ironman distance triathlon in seven hours 54 minutes 43 seconds at St George in Utah on Saturday.

Parker said the event was harder than the Hawaiian Ironman world championships, where she finished second in her age group six years ago.

The 32-year-old from Newcastle was left a paraplegic after a 2017 bike accident.

Parker was preparing in the Las Vegas heat for the 70.3 worlds when she had to wait in a car after a training session.

She had her feet on the dashboard and because Parker has no feeling in that part of her body, she did not realise they were being scorched by the sun through a red-hot windscreen.

She ended up with severe burns and had to spend time in a St George hospital for treatment.

Two nurses and a doctor worked with race officials to help Parker through the race, dressing her wounds after the 1.9km swim and the 90km bike.

"They were unbelievable, I couldn't ask for a better support system here," Parker said.

"I'm sore, it was the hardest race, the hardest course that I have ever come across.

"I've raced Kona twice and it was harder than that.

"My arms were killing, but I got it done and it was a great experience. It will make every other Ironman easy."

Burnt feet and toes weren't the only drama Parker endured leading into the race.

Just days after she was released from hospital, Parker and her trainer Brad Fernley were involved in a car crash in which both vehicles were written off, although they emerged unscathed.

Parker said she had to stop at times on the steep hills during the 21.1km run leg. She was was first women's para racer across the finish line, almost 45 minutes ahead of her nearest rival.

An unusual storm system also brought heavy downpours and gusty wind.

Norwegian Gustav Idan successfully defended his men's elite 70.3 world title, crossing the line in 3:37:13, while Australian Sam Appleton was eight minutes behind in ninth place.

British star Lucy Charles-Barclay won her first 70.3 world title in 4:00:20 and Ellie Salthouse was the first Australian elite woman in 14th.

Meanwhile, this year's World Triathlon sprint and relay championships have been called off due to a surge in COVID-19 infections in Bermuda.

The event was scheduled for October 15-17 in Bermuda, where COVID-19 cases are at their peak.

The Atlantic island has recorded 4218 COVID-19 cases and 38 deaths since the pandemic began, according to a Reuters tally.

Governing body World Triathlon and the Bermuda Local Organising Committee said in a joint statement that they used a tool provided by the World Health Organisation (WHO) to conduct a risk assessment of the event, amid the changing conditions.

"The analysis considered the island's recent spike in COVID-19 infections in addition to the Bermuda Hospital's elevated COVID-19 patient intake, and the organising committee in consultation with World Triathlon made the decision not to proceed with the October event," the statement said.