He admitted as much over morning tea with residents of a retirement village in the NSW South Coast town of Nowra on Thursday morning.

"I've been very lucky I've gotta say," the Labor leader said in an exchange captured by the pack of cameras trailing his election campaign.

"A lot of my colleagues, a lot of parliamentarians [have caught the virus] ... because we mix and go around.

"But so far, crossed fingers."

Hours later, his luck had run out.

A routine PCR test ahead of a planned visit to Western Australia confirmed Albanese had contracted the virus, forcing him into isolation in Sydney and off the campaign trail for seven days.

The Labor team had prepared for the prospect of its leader being forced into a COVID-induced hiatus.

Backup plans months in the making have been swung into action in order to keep pace with Scott Morrison as the campaign enters its third week.

Labor frontbenchers, including Richard Marles, Tanya Plibersek and Jason Clare, will step up.

Albanese is optimistic.

But the COVID bout is a major disruption, the latest shock in a roller-coaster past month from the man who wants to be Australia's next prime minister.

Albanese was riding high as Parliament adjourned just after 8pm on March 31.

He'd just delivered his budget reply, a speech which combined a major aged-care policy announcement with stinging criticisms of Scott Morrison's character and an aspirational vision for Australia.

The address, widely seen as among the best Albanese had delivered, ended with a demand of the Prime Minister.

"Call the election; call it now, and let the people of Australia decide."

His impatience was understandable. The Coalition was ripe for the picking, well behind in the opinion polls and tearing itself apart.

Two days earlier, Liberal senator Concetta Fierravanti-Wells had unleashed on the Prime Minister as lacking a moral compass and being unfit for the role.

The withering attack was launched against the backdrop of a factional war inside the NSW Liberal Party, which had cast a cloud over the status of up to 12 candidates - including two ministers - right up until election eve.

Morrison's stocks had never been lower, Albanese's arguably never higher.

Fast-forward three weeks and the momentum which Labor and its leader carried into the election had stalled.

The first published opinion polls of the campaign showed Labor still ahead of the Coalition, but Albanese's popularity had slumped after a string of missteps headlined by the unemployment-rate gaffe.

The stumbles sapped the leader's confidence. Labor MPs have privately conceded as much.

There was also disquiet internally about some early policy calls, including the decision to abandon a promised review into the rate of JobSeeker.

The decision has alienated Labor's grassroots base, for marginal if any gain. What harm in a review, they wondered.

Albanese couldn't catch a break. Even an appearance at Byron Bay's Bluesfest, where Albanese was invited to introduce working-class hero Jimmy Barnes to the stage, was met with a mixed response from punters.

Already committed to a safe, "small target" strategy, Labor's approach narrowed further as the anxiety built ahead of the first face-to-face showdown between the leaders of the campaign.

Albanese barely ventured beyond the outskirts of Brisbane on visits to flood-ravaged homes, a local RSL, a manufacturing plant and a trucking depot in the three days before Wednesday's leaders' debate.

He made just one announcement in that time, a commitment to boost funding to a veterans-led disaster relief organisation which was quickly matched by the Coalition.

With no fresh policies to sell, Labor turned to scare tactics, rehashing Bill Shorten's "Mediscare" campaign from 2016 and refusing to resile from claims the Coalition planned to force pensioners onto the cashless debit card.

On both fronts, the key antagonist was not the Labor leader but his treasury spokesman, Queenslander Jim Chalmers.

Industrial relations spokesman Tony Burke also joined the campaign trail on Tuesday, he and Chalmers flanking their leader like a Praetorian guard.

The pace of the campaign was far from frenetic, belying the urgency and impatience which Albanese displayed in the weeks before it was called.

His only public appearance on Wednesday, a visit to transport giant Toll's warehouse just south of Brisbane, wrapped up before 10am, leaving the bulk of the day to prepare for the debate.

Workers told The Canberra Times that Christine Holgate had visited the Berrinba depot not long after becoming chief executive of Toll Global Express.

If anyone knows what Scott Morrison's public wrath can do to one's career, it is the former boss of Australia Post.

Albanese couldn't afford to be monstered by Morrison later that evening.

And he knew it.

As the home of the Brisbane Lions and host of an annual men's Test cricket match, the Gabba stadium has seen some thrilling contests over the years.

The leaders' debate was not one of them.

Albanese and Morrison stuck rigidly to their prepared lines as they answered questions on topics including housing, China and the NDIS from an audience of 100 undecided voters.

The tone was far different to what's customary in their question time duels, a seemingly deliberate tactic from both leaders to appease voters fed up with the mudslinging which characterises modern politics.

The only flashpoints came on national security, a traditional Coalition strength and Labor weakness.

Albanese stumbled on the matter of asylum seeker boat turn-backs. Morrison, dressed in a maroon-coloured tie to suit his surrounds, pounced.

But the senior Labor figures in the room, including Chalmers and Burke, believed Albanese more than made up for it with a piercing line of attack on the Coalition's failure to torpedo the security pact between Solomon Islands and China.

Albanese doubled down on the criticism when he fronted reporters at Shoalhaven Starches ethanol distillery in Nowra the following morning, a sure sign Labor strategists believed the attack had, or would, cut through with voters.

One view within Labor is that the "Pacific stuff up", as Albanese termed it, can be weaponised for the dual purpose of undermining the Coalition's credibility on national security while serving as the latest example of the government's failure to respond when problems arise.

The security deal now sits alongside the Black Summer bushfires, the vaccine rollout and the flood response at the centre of Labor's central campaign line: Scott Morrison doesn't show up when it matters.

Plates of chocolate-chip biscuits and slices were laid out when the campaign circus arrived at Symons House retirement home in Nowra just after 11.30am on Thursday.

Albanese, Burke and Gilmore MP Fiona Phillips received a warm reception from most of the residents.

But others hung back, content to sip on their tea or coffee as the swarm of cameras and journalists filled their communal lounge.

One resident, Marlene, was sceptical of the man who would be Prime Minister.

"One day he's telling you this. The next day he's telling you that," Marlene said of Albanese.

As a retired nurse, she wondered how Labor would find the staff to meet its pledge to have one on-site, 24/7, at every nursing home.

"They have people [nurses] retiring and leaving in droves. So where are they all going to come from?" she said.

"Policies are cheap."

Living in one of nation's most hotly contested seats, Marlene's views matter. She's voting for Liberal Andrew Constance - and Scott Morrison - on May 21.

Dark clouds and light drizzle greeted the Labor leader as he touched down in Sydney on Thursday afternoon.

In his first proper campaign event in his home city, Albanese made a beeline for Bennelong, a seat Labor hopes to win from the Liberals following the retirement of former tennis champion John Alexander.

The camera pack hovered around Albanese as he staged a coffee catch-up with Labor's candidate, Jerome Laxale, in the Ryde shopping strip.

A group of schoolchildren, none quite tall enough to see above the cameras, wondered what the fuss was about.

As Albanese turned to depart, a smiling face and supportive voice caught his attention.

Her name happened to be Karma. What a name, Albanese replied.

"I hope it brings you some," she shot back in a clear message of support for Labor.

Fewer than four hours later, Albanese revealed he had COVID-19, upending a campaign which was just kicking into gear.

The media scrum following Albanese was supposed to be on a plane to Western Australia on Friday morning.

Instead, it had packed into a room in the Commonwealth Parliamentary Offices in Sydney, desperate to hear how Labor would run a campaign with its leader confined to his home for the next seven days.

"Well, the boss has got the bug, so you got me," Labor's campaign spokesman, Jason Clare, said.

The opening message set the tone for the press conference. Labor is looking at the positives.

Clare said there would be no de facto leader to campaign in Albanese's absence. Labor would instead lean on its line-up of experienced and high-profile frontbenchers to carry the load.

Labor finance spokeswoman Katy Gallagher on Friday afternoon travelled with Clare to the hyper-marginal Labor-held seat of Macquarie, speaking with farmers affected by the recent floods.

Clare said Labor's approach would highlight the strength and depth of its team at the same time as exposing Scott Morrison to more scrutiny and attention.

Ordinarily more attention would be a good thing for a prime minister seeking re-election.

But Clare thinks that logic doesn't apply to Morrison, so pungent is the stench surrounding his government.

It's hard to know what logic can be trusted in circumstances so unprecedented.