Australia is closing its borders to all foreigners who aren't permanent residents in a bid to slow the spread of coronavirus.
About 80% of Australia's more than 700 cases have come from returned travellers, or people who've been in contact with them.
The border closure, in effect from 21:00 local time on Friday (10:00 GMT), has upended travel plans, and is likely to split families.
It's also created uncertainty for roughly two million temporary visa holders in Australia.
So if you're in that situation, what do the latest changes mean?
If you want to leave Australia
Bear in mind the situation is changing fast and that airlines may continue to cancel flights and routes.
Also keep abreast of what restrictions there may be upon return to your home country.
For UK citizens, the Foreign and Commonwealth Office (FCO) advises to keep across guidance from governments in Australia and at home.
If you want to stay
Your visa is valid for its full duration as long as you meet its requirements - note this may include maintaining a job.
If its nearing expiry and you want to stay on, you need to apply for a new one before it elapses.
Australia is allowing people to apply to waive a "no further stay" condition - which would typically prevent visa from being renewed. This condition is common on many backpacker and temporary work visas, for instance. Remember applications are necessary.
If your visa has expired and you want to remain, you need to apply for a "bridging visa". This will allow you to stay while you await the results of your new visa application.
"Any visa application will be assessed considering the Covid-19 enhanced border measures and an applicant's individual circumstances," an Australian government spokesman said.
Students who need to fulfil study requirements also have the option to apply for an exception, which will be granted on a case-by-case basis.
What happens if you're outside Australia?
You will not be allowed back until the travel restrictions have been lifted - and no-one knows when that may be. This also applies to temporary visa holders currently in Australia who may have planned to leave and come back.
If you've already obtained a temporary visa and have not yet entered the country, you will need to re-apply once the restrictions are lifted.
You can enter Australia if you're a permanent resident, but the advice is to contact the office which granted your visa when you're able to travel.
What happens if you stay?
Migration advocates and the Labor opposition have raised concerns that temporary work visa holders who stay in Australia could lose out if their employment is terminated in the event they lose their job.
An economic downturn may make it hard for foreign workers to find a replacement job. Many will also not have access to welfare benefits or subsidised medical treatment.
Advocates are calling for more support. Already, some supermarket chains have pledged more shifts for international students.
Australia's agricultural and farming sector is currently lobbying Canberra to extend the visas of working holidaymakers and seasonal workers.
Where can you find help?
UK consular officials have advised people to check Australia's immigration site for changes on visa restrictions.
"I know that recent events have created a lot of uncertainty and concern for British people in Australia," said UK High Commissioner Vicki Treadell.
"We encourage British people in Australia to follow the health advice of local authorities."