Spinner Jess Jonassen will miss the first two matches of the Australian women's T20 tri-series in Ireland after testing positive for Covid-19 on the eve of the squad's departure for the United Kingdom.

The spin-bowling all-rounder is being isolated at home in Brisbane and will miss the first two matches of the four-game tri-series. The Queenslander will now fly to Northern Ireland next Monday to join the team for the remainder of the series.

Tasmania all-rounder Heather Graham has been called into the squad as back-up and will arrive in the United Kingdom in the coming days.

The T20 tri-series, which includes two matches apiece against Ireland and Pakistan and begins on July 16, will serve as preparation for the Birmingham Commonwealth Games, where Australia will begin their bid for a gold medal against India on July 29.

Jonassen's absence from the first two T20 matches could open the door for another spin-bowling all-rounder in Grace Harris -- who earned a recall for Australia's Ashes T20s against England in January in place of an injured Beth Mooney -- or leg-spinner Amanda-Jade Wellington.

The Australian squad arrived in Belfast on Tuesday and had several days to prepare for their opening T20 against Pakistan on Saturday (1 am Sunday AEST).

Australia's squad: Meg Lanning (c), Rachael Haynes (VC), Darcie Brown, Nicola Carey, Ashleigh Gardner, Heather Graham, Grace Harris, Alyssa Healy, Jess Jonassen, Alana King, Tahlia McGrath, Beth Mooney, Ellyse Perry, Megan Schutt, Annabel Sutherland, Amanda-Jade Wellington