Before the shutdowns and eerie images of a barren Times Square, before the bungled US federal response to a virus that has since killed 549,000 Americans and nearly 2.8m people worldwide, before most people even had a date they could loosely observe as a pandemic anniversary this past month, there was the Diamond Princess.

The cruise ship departed from Yokohama, Japan on 20 January 2020 for a roundtrip tour of southeast Asia. On board was an 80-year-old passenger from Hong Kong who had recently visited Shenzen, Guangdong Province, China. At the time, there were only four confirmed cases of the then-unnamed Covid-19 virus outside mainland China; within two weeks, the ship would be stalled in the Japanese harbor under quarantine as the largest coronavirus outbreak outside Wuhan – 712 people, 14 of whom would die.

The Diamond Princess became both a closely observed coronavirus case study – a closed-loop epidemiology experiment for the novel virus – and a dire warning about the contagion’s asymptomatic carriers and airborne spread. But to the 3,711 people aboard (2,666 guests and 1,045 crew members), the two-week quarantine was a metastasizing real-life horror film tentacled by pre-existing dynamics of class and nationality – an experience of terrifying paralysis, confusion and collapse chronicled in The Last Cruise, an HBO short documentary released this week.

In 40 dread-filled, unsettling minutes, The Last Cruise evokes the fear and anxiety of coexisting with a then novel, amorphous, poorly understood threat through mostly cell phone footage by passengers and crew. It’s not so much a retrospective – we’re not out of the pandemic woods yet, of course – as “an origin story”, the film’s director, Hannah Olson (who also recently made Baby God), told the Guardian. By hovering tightly to the perspectives of passengers and crew, The Last Cruise revisits “the way we felt in the early days of the pandemic – the moments of dismissal, denial, fear, uncertainty, panic”.

Unlike last October’s Totally Under Control, which snap-metabolized the US government’s galling failures to contain the coronavirus from film-makers Alex Gibney, Ophelia Harutyunyan and Suzanne Hillinger, Olson purposely does not include experts or epidemiologists in The Last Cruise. There’s no scientific retrospective on how the virus traveled through the ship’s air ducts, how Japanese health officials undertook a disorganized, inconsistent testing and isolation process (an untold number of passengers were never tested, and 57 people tested positive after they were released from the boat), or how various national governments managed talks rescue.

Instead, the gradual slide into a 21st century Titanic story of disaster shouldered unevenly by class plays through a verité collage of self-recorded videos escalating in desperation and fury. For vacationers, including about 400 Americans, holiday selfies and ebullient cell phone diaries curdled into grim recordings of listless days contained to a ship cabin, clogged toilets, air ducts suddenly taped over and intercom information drops whose import are made more unbelievable by the forced, chipper neutrality of the captain’s tone. While the viral threat boxed passengers in their sunlit cabins, the crew were forced into potential exposure in shared mess halls and undersea sleeping quarters, their labor necessary for the other two-thirds’ continued safety.

Olson began work on The Last Cruise from afar, as passengers remained quarantined on the ship and New York hovered in a state of denial about a virus that would eventually claim 31,000 residents. “I was watching the headlines like everybody else and seeing ‘ship quarantined in Japanese harbor, 500 cases of Covid on board’,” she recalled. She started collecting the ample social media output from those onboard, several of whom are interviewed in The Last Cruise – passengers frustrated with a limp, cold meal; crew justifiably terrified about working in shared facilities to prepare said meal without protective equipment, cramped next to coughing co-workers, left exposed by safety procedures one Japanese infectious disease expert on board later described as “completely inadequate”.

“I started wondering who gets to count as a human being?” Olson said. “Who gets to take cover in a crisis? Who gets to be in quarantine, and who has to be a human shield? That’s something I was watching play out in my own life in New York in March of last year, as I watched the rich head to their bunkers and [the term] ‘essential workers’ [was] born.”

At the same time the Centers for Disease Control and Prevention sent representatives aboard the ship in Hazmat suits, the US government advised against wearing or buying masks as a preventive measure; on 29 February, the US Surgeon General tweeted “Seriously people – STOP BUYING MASKS!” as they were “NOT effective in preventing general public from catching #Coronavirus.” The disconnect between “what my government was telling me and what I was seeing first-hand on Facebook” drew Olson deeper into the saga, as she amassed hundreds of hours of footage.

Though she was in contact with numerous people aboard the ship, most of The Last Cruise was filmed without her direction, by everyday citizens attempting to make sense of an unknown crisis unfolding in real time, and in some crew cases, breaking employment NDAs to call for help (the final people removed from the ship, in early March, were 69 Indonesian crew members). “Just as much as it’s a film about the feelings of the early crisis, it’s also about how we narrate our lives,” said Olson, “and what happens when cell phone vacation footage or a selfie you make when you’re working becomes part of this global story, and the timing and the details matter.”

From a laymen’s perspective, “so much of the experience of the onset of this pandemic was the information vacuum”, said Olson. But “what was appalling to me making this film was how much we knew and how many lives could’ve been saved if we would’ve listened to the lessons of this ship”. The Last Cruise is a “time capsule” of what scientists and government officials knew in February thanks to observing that ill-fated cruise ship: that the virus spread through asymptomatic carriers (including the Diamond Princess’s patient zero); that widespread testing of all people, including those without symptoms, was key to quantifying the threat and containing the spread; that the virus was transmitted through the air, including through ventilation systems.

Yet it would take until 3 April for the CDC to advise Americans to wear masks, and until 27 April to recommend testing for “people without symptoms” according to state and local guidelines. By that point, the US had one million confirmed cases of Covid and 56,000 deaths – a preventable tragedy of government incompetence, scientific hubris, and infuriatingly dangerous inanity by then-President Donald Trump documented more comprehensively in Totally Under Control. “It was like a horror film that I was watching happen in the social media footage and started to compile it,” said Olson of her initial collation process in February and March, “and then this larger horror film as I’m watching these lessons be ignored.”

“The information we got from the Diamond Princess was our chance. It gave us all of the information we needed,” said Olson. The Last Cruise, like Totally Under Control, reveals once again how “the people who had the power to make changes did not listen”, she said. “And the horror that took place on the boat actually engulfs the entire world.”

• The Last Cruise is now available on HBO and HBO Max (and via Foxtel in Australia), with a UK release to be announced