The coronavirus spread through a Tasmanian hospital from two elderly patients who had been passengers on the Ruby Princess cruise ship, hopping from healthcare worker to healthcare worker at end-of-shift handovers and forming clusters among the attendees of planning meetings.

The North West Regional and North West Private hospitals in Burnie were closed and 1,300 staff were sent into a mandatory quarantine, along with their families, on Easter Sunday when earlier efforts to control the spread had failed.

An interim report into the outbreak, which has been linked to 11 deaths, found that 20% of the 73 healthcare workers who later tested positive to Covid-19 turned up to work when they had respiratory symptoms because they did not want to leave colleagues shorthanded and believed their symptoms related to other chronic respiratory conditions. Some worked as many as six days while symptomatic.

Speaking to reporters in Hobart on Thursday, premier Peter Gutwein said no one should be blamed for the outbreak.

“This is simply a case of people going about their lives, going about their jobs, while this dreadful set of circumstances has ensued and has wreaked havoc and misery on so many people,” he said.

Gutwein said Tasmania would learn from the outbreak.

By the time the first two cases of Covid-19 infection among staff at the hospital were reported to the Tasmanian Health Service on 2 April, 11 other people had already experienced symptoms, the report by Tasmania’s director of public health, Dr Mark Veitch, and deputy director, Dr Scott McKeown, found..

“Following these initial infections, multiple potential chains of direct person-to-person transmission were apparent,” the report said. “These were between staff, or between staff and patients (in both directions). These transmission events occurred within the different northwest healthcare facilities through either the transfer of infectious patients or through infectious staff working in multiple locations including aged care facilities.”

Seventy-seven per cent of staff who later tested positive attended work during the infectious period, which begins 48-hours before the first symptoms are detected. Just over half did not attend work when they had symptoms, and 29% experienced symptoms on their last day of work before calling in sick. By 21 April, 114 cases, including 22 patients and 19 family contacts of healthcare workers, had tested positive.

Veitch and McKeown said that staff continuing to work while symptomatic, meetings in small rooms, shortcomings in infections practices and “incomplete or delayed” identification of close contacts contributed to the virus’s rapid spread. The hospital still runs on a paper-based system, which they said made it difficult for contact traces to identify the timing of handovers or late changes to the roster.

They did not find any evidence of inappropriate social gatherings by staff.

Similarly, the report found that strict adherence to the 14-day quarantine, which lifted on 27 April, helped bring the outbreak under control.

“Throughout the outbreak the diligence, professionalism and commitment of all staff involved was always on display,” Tasmania’s chief medical officer, Prof Tony Lawler, said. “The resilience of staff at all affected facilities and services needs to be acknowledged, and the community should be proud of the service provided under incredibly difficult circumstances.”

Lawler made 17 recommendations, including transitioning to an electronic system for rosters and clinical reports, limiting staff and patient movement between facilities, and addressing the underlying reasons behind staff working when sick.

He also recommended hospitals implement consistent staff screening processes, introduce a training campaign and buddy system to ensure adherence to infection control measures and use of PPE, and said the northwest should have dedicated registered nurses working on the Covid-19 response.

The Tasmanian government said it would implement the recommendations in full.

