An outbreak of COVID-19 following a voyage of the Ruby Princess cruise ship was "not some accident" but was "very likely to happen" due to preceding events, a Sydney court has heard.
A class action lawsuit began on Wednesday in the Federal Court in Sydney, two-and-a-half years after the ill-fated trip.
About 2,600 passengers embarked on the voyage on March 8, 2020, before the ship returned to Sydney amid an outbreak of illness.
More than 660 people tested positive for COVID-19 in subsequent weeks and 28 people died, according to a previous inquiry into the matter.
The class action alleges that Carnival, the charter of the vessel, and Princess Cruise Lines, the owner and operator, breached duties of care by allowing the trip to proceed.
It claims there was a failure to take appropriate measures to protect passengers from the risk of infection and alleges a breach of Australian Consumer Law.
Barrister Ian Pike SC, representing lead plaintiff Susan Karpik, said by the time the Ruby Princess departed, there had been 100,000 confirmed cases of COVID-19 globally.
There had also been outbreaks on board the Diamond Princess and Grand Princess.
"What occurred at the end of the voyage ... was not some accident, it was something that was very likely to happen in light of what occurred prior to the boat sailing," Mr Pike said during an opening address.
By February 20, more than 600 people on board the Diamond Princess had tested positive for COVID-19.
"That accounted for the majority by far of the world's cases of COVID-19 outside China," the barrister said.
Mr Pike alleged that at all times Carnival and Princess knew, or ought to have known, there were not sufficient supplies to manage an on-board outbreak, which the respondents deny.
The court was shown a series of emails, including one sent by the Ruby Princess's senior physician, Ilse von Watzdorf, to NSW Health the day before it sailed.
She warned she was not able to guarantee there would be enough masks for everyone that may present the following day — and said the same applied to swabs.
In response, she was advised it was "important to have a good supply going forward" and to purchase some in one of their next ports.
Other emails reveal discussions within Carnival about taking guest temperatures at embarkation.
"We need to get on with this as quickly as possible," the company's president, Sture Myrmell, wrote in an email on March 11.
He said Royal Caribbean had already implemented the measure and they were "way behind", having been "talking about it for four weeks now".
Mr Pike said that was a "simple precaution that could have been introduced".
"In circumstances where they knew they could not implement the obvious precautions because of inadequate supplies, this boat never should have sailed," he said.
David McLure SC, representing Carnival and Princess, said his opponents have put the case on the basis the duties of care owed stemmed from "the relationship of occupier and entrant".
"We describe it as a juridical fact that there is no decision of any court in this country that has recognised the kind of duties that the applicant contends were here," he said.
The duties alleged against Carnival included the duty to "cancel the cruise to eliminate the risk", Mr McLure said in his opening address.
He argued that when a person decides to go on a cruise ship, they necessarily make a choice to have some close encounter with other people.
"It's not correct to say that when a person is on a cruise ship, they are then removed from the ability to take themselves out of any particular setting where they feel uncomfortable because, for example, there are too many people there or people who they think are ill."
He said at least one thing a person could choose to do would be to "isolate themselves in their stateroom with their open-air balcony".
In court documents, Carnival argues several defences, including that the risk of a passenger contracting a contagious disease was "an obvious risk" to a reasonable person in the circumstances.
It claims the passengers knew or were presumed to have known that risk and, by going on the voyage, they "voluntarily accepted" that risk.
Carnival claims the risk could not be avoided by the exercise of reasonable care and skill.
The trial is expected to run for four weeks.
