While suburbs face the prospect of being locked down in a bid to curtail the spread of the deadly virus, federal politicians are travelling from across the country to Canberra for an extraordinary one-day sitting of the Federal Parliament.

It leads to the question: why are they doing so when the rest of the nation is being urged to hunker down?

The simple answer is the Government needs to pass legislation in order for it to spend the billions of dollars in response to the coronavirus pandemic.

The legislation that needs to be dealt with includes the urgent coronavirus economic stimulus bills designed to keep the nation financially afloat and help the most needy.

Who will be coming to Canberra?

There are 227 federal politicians that sit in the Parliament, across two chambers.

Of those, 129 politicians must be present in Parliament House for the House of Representative and Senate to function.

That means almost half of the Parliament has been excused to limit the number of people needing to travel to the nation's capital.

Typically 151 politicians cram into the House of Representatives. ( ABC News: Matt Roberts )

Will the 129 sit all day?

In short, no.

To deal with any business, the Parliament needs a quorum, which is 31 MPs in the Lower House and 19 senators in the Upper House.

But if there are any votes on legislation, or attempts to change the day's schedule, all the politicians present at Parliament House will rush into the chambers.

If a division is called for a vote to change the proceedings, a minimum of 76 people will be required in the House of Representatives and 39 in the Senate in some circumstances.

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The Government insists those within the chambers will adhere to social distancing guidelines at all times.

It's even possible there may not be any votes.

That's because the major parties have signalled they are in agreement about the economic package.

Instead, the legislation could pass "on the voices" if no-one yells out "nay" when asked if those present agree to the measures before the Parliament.

This can all happen because of "pairing" arrangements that allow two MPs or senators from opposite sides to agree they will be absent and their votes can cancel each other out if required.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 3 minutes 7 seconds 3 m 7 s Scott Morrison foreshadows stronger social distancing measures.

Which politicians will have to come to Canberra?

Any politician who is self-isolating will get a leave pass.

Home Affairs Minister Peter Dutton has been discharged from hospital and is planning to attend if he gets a clean bill of health.

There are two other senators who have been confirmed to have coronavirus, Queensland LNP senator Susan McDonald and NSW Liberal senator Andrew Bragg. They won't be there.

Peter Dutton was the first federal politician diagnosed with coronavirus. ( ABC News: Tamara Penniket )

Anyone travelling from a remote community, or facing a long journey to get to Canberra, will be able to skip attending.

Other members of Parliament with a compromised immune system will also be able to stay home.

Greens Senator Jordan Steele-John, who uses a wheelchair and has cerebral palsy, is staying away after getting medical advice.

Crossbenchers are mixed in their approach. Senators Jacqui Lambie and One Nation leader Pauline Hanson don't plan to come. But two of Centre Alliance's three politicians will attend.

Susan McDonald will skip Parliament having been diagnosed with coronavirus. ( Supplied: Facebook )

Will it just be politicians at Parliament House?

In a full parliamentary sitting week, it's estimated there are up to 5,000 people hurrying to work and meet inside the Federal Parliament.

But there won't be much of the usual hustle and bustle. MPs are only bringing essential staff.

Former parliamentarians, most lobbyists and volunteers won't be able to come in to restricted areas even if they have a pass to access the building.

The usual stream of school excursions have been cancelled or postponed.

Even the Parliament's eateries will be putting in measures to limit handling of food and seating spread out to prevent the spread of coronavirus.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 8 minutes 54 seconds 8 m Treasurer Josh Frydenberg outlines the details of second stimulus package

Why can't politicians work from home?

Government backbencher Barnaby Joyce has wondered why can't the Parliament go virtual and allow politicians to "hit yay or nay from their office?"

According to the clerk of the House of Representatives, Claressa Surtees, it's pretty simple, and outlined in the foundation document of the nation — the constitution.

She points out that Section 39 of the constitution refers to the need for the "presence" of a fifth of the Parliament for a quorum to validate any decisions that are made.

"This requirement has always been interpreted as meaning that 'the presence' means physical presence," the clerk said.

In advocating for a virtual Parliament, Mr Joyce gave a warning of the consequences of it going ahead like normal.

"Parliament is designed to spread COVID-19. Politicians touch hundreds of hands then jump in a plane and fly to boarding school in Canberra," he said in a statement to Channel Ten.

"Then after that take what has been picked up in that process, jump back on a plane and fly to every corner of Australia."

The May budget has been postponed until October now, so it's unclear how many months might pass before politicians are back in Canberra again.

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Will we see the usual political blow-ups?

The Parliament is only expected to sit for a single day, as politicians work to pass the laws and get home to their electorates.

The only matter listed on the agenda is "urgent stimulus package and other immediate business".

The Parliament will practise social distancing, meaning politicians will be spaced out across the usually crammed leather benches.

And don't expect the usual raucous questioning and sledging of Question Time.

It will go ahead with the minimum number of people required to ask and answer the questions.

There won't be anyone in the public gallery for Question Time either. There will be fewer attendants in the chambers, and the usual practice of handing around glasses of water is likely to be canned.

The Parliament's cleaners will have the antiseptic spray in the quick-draw holster, particularly on the doors and other surfaces that many people touch and at the building's security gates where hundreds of people come in and out of the building for work each day.