The 21-year-old triple Commonwealth Games gold medallist tested positive just days after a promotional photo-shoot on the Gold Coast.

The news sent shockwaves through the Australian swimming team as its biggest names were also at the launch and preparing for upcoming world championships.

The news comes as fellow Tasmanian and 2018 Commonwealth Games teammate Stewart McSweyn also battles to qualify for this year's Games in Birmingham suffering the after-effects of COVID.

Launceston-born Brisbane-based Titmus reportedly left Wednesday's race suit unveiling event early feeling unwell.

Swimming Australia subsequently confirmed her positive test.

"Ariarne has returned a positive test and has been isolating appropriately," a spokesperson was reported as saying.

Dolphins teammates including Emma McKeon, Zac Stubblety-Cook and Mack Horton were at the launch with some scheduled to fly to Spain this week for a camp ahead of world championships in Budapest on June 18.

"Those other athletes who attended the launch are following the relevant precautions as set out by the team doctor and all have returned negative tests," the SA spokesperson said.

"There is no delay to the planned travel over the weekend."

Several of the national team members, including Mollie O'Callaghan and Elijah Winnington, also train with Titmus at the St Peters Western club.

The news broke less than a fortnight after Titmus was confirmed in the Australian team for this year's Commonwealth Games having broken Katie Ledecky's long-standing 400m freestyle world record at the national championships in Adelaide.

She had also come close to the 200m world record.

The reigning Tasmanian Athlete of the Year, Titmus had opted out of competing at the world championships in order to focus on the Commonwealth Games which begin in late July.

At the unveiling of Australia's suits for the Commonwealth Games, Titmus said: "When I pull on a Speedo green and gold suit, I know I'm going to swim fast.

"There is a special feeling representing your country and wearing a suit I feel comfortable in takes my performance to the next level."

McSweyn, 27, is also battling to be fit for Birmingham. The King Islander, who contested both the 5000 and 10,000m at his maiden Commonwealth Games on the Gold Coast, has struggled to regain form after contracting COVID.

Basing himself in London, McSweyn was far from his best in recent 1500m Diamond League races in Doha and Birmingham.

His respective times of 3:48.67 and 3:44.14 were well short of his 3:29.51 personal best set a year ago.