Australia's players were united in camp on Monday, with an intra-squad warm-up match on Tuesday before the first ODI in the multi-format series on Thursday in Adelaide.
While some members moved to South Australia as early as last week, players from NSW and Victoria were isolating before arriving by charter flight and car to minimise COVID-19 risk.
Among those missing, however, are Sophie Molineux and Georgia Wareham, with the spinners both injured for the Ashes ODIs, Test and T20s.
Jonassen is returning to the squad after missing the October series against India with a leg injury, while Perth spinner Alana King has been called into the squad.
Shouldering more responsibility is of no concern to Jonassen, who has taken 192 wickets across all formats for Australia and is the world's No.1 ranked ODI bowler.
"I've looked at myself s trying to lead this spin group anytime I'm a part of it," Jonaseen said.
"I don't really feel any extra expectation or pressure or weight on my shoulders.
"I've been fortunate enough to play for Australia for a number of years and be involved in the set up for a number of years.
"I try and just impart whatever experiences I've had with whoever the other spinners are."
Ash Gardner is expected to take on more of a spinning role, with King marginally winning out over Amanda Jade-Wellington to be selected.
Meanwhile, Australia's players have stated they will follow whatever protocols required to protect them from COVID-19, with flow-on effects well beyond the Ashes.
Players must dine outdoors and only move in small numbers, while gym sessions have also been limited to pairs and done outdoors in the early stages of the camp.
The series has already been impacted by the virus, with a member of England's support staff testing positive shortly after arriving last week.
Officials are keeping Australia and Australia A players apart — with the exception of Tuesday's match — to avoid an outbreak impacting both camps.
Players from the 'A' camp will be used as cover in the Ashes if an outbreak occurs, while any player who contracts the virus late in the series would not be able to travel to New Zealand to quarantine for the ODI World Cup.
"It's just been a matter of listening to the advice that we're getting from the experts and doing everything that we can," Jonassen said.
"We're all human, the same as everybody else. We all have sort of similar concerns and similar worries.
"Obviously with World Cups or big important series, it adds another element.
"But everyone has similar stresses as well with whether they can see family or whatnot."
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