For the first time in Australian history, a Level Four travel ban has been instituted on the entire world by the Federal Government.

This unprecedented move is intended on stopping all Australians from travelling overseas to limit the spread of coronavirus.

The travel ban was announced by Prime Minister Scott Morrison earlier today.

Scott Morrison has told Australians not to travel overseas. (AAP)

"We are upgrading the travel ban on Australians to Level Four for the entire world," Mr Morrison said.

"That is the first time that has ever happened in Australia's history. The travel advice to every Australian is 'do not travel abroad'.

"Do not go overseas. For those who are thinking of going overseas in the school holidays – don't."

Most coronavirus cases in Australia are from people coming into the country from overseas.

For most people, the new coronavirus causes only mild or moderate symptoms, such as fever and cough. For some, especially older adults and people with existing health problems, it can cause more severe illness, including pneumonia. (Christoph Soeder/dpa via AP)

What does a Level Four travel advisory mean?

Level Four is the highest rating for travelling danger issued by the Department of Foreign Affairs.

Normally reserved for the most war-torn and chaotic countries, the Level Four category is simple: Do not travel.

Yemen is one of the few countries to have an existing Level Four warning. (AP)

"At Level Four, your health and safety is at extreme risk," the Smart Traveller website states.

"This may be because of a high threat of terrorist attack, conflict, violent social unrest, widespread infectious disease or critical levels of violent crime. It could be a combination of risks.

"If you get into trouble, the Australian Government may be unable to help. In most cases, our ability to provide consular assistance in these destinations is extremely limited."

Countries which were at a Level Four before today included Somalia, Burundi, Yemen, Syria, Iraq and Afghanistan.

Countries which were not at Level Four before today included North Korea, Sudan, Haiti and the Democratic Republic of Congo.

Afghanistan was one of a handful of countries to already have a Level Four warning. (AP)

While the travel advisory includes the risk of widespread infectious disease as a reason for a Level Four, violence is typically the reason for the category.

"Any travel by Australian officials to 'Do Not Travel' locations is subject to high-level approval," Smart Traveller states.

"It includes rigorous risk assessment and movement planning usually involving the use of armoured vehicles."

What happens if I do go overseas?

Most travel insurance policies will not cover any destination at a Level Four level.

As a result, those travel insurance policies would be voided for any Australians travelling overseas at all.

The Smart Traveller website does not mince words about Level Four countries.

"Understand that you could die. Make sure you have an up-to-date will, an enduring power of attorney. Designate appropriate insurance beneficiaries."

(Supplied)

Read more: Updates on the coronavirus pandemic