Already had COVID? What you need to know about travelling overseas

There are various places you can get a test, including at Sydney and Melbourne airport (but arrive early to ensure you have enough time to get your results).

If you're overseas and need to transit to another country that requires a COVID test on arrival, some companies including Sloane Street Testing in the UK (sloanestreettesting.co.uk), My Healthcare Clinic in the US (myhealthcareclinic.com), and FastTest in Canada (fast-test.ca) offer express 'fit to fly' PCR test results or travel exemptions, ranging in price from $140 for a recovery certificate to $370 for 12-hour express PCR results.

If you've recovered from the virus within 30 days of your trip, it's worth organising an exemption certificate (see below) before leaving the country to avoid any unexpected problems.

From April 18, the Australian government will longer require proof of a negative COVID-19 test in order to enter the country, so you won't need to get tested in order to return home.

I've tested positive for COVID-19 and I am travelling overseas soon – what now?

If you've tested positive for COVID-19, Australian states currently require you to isolate for at least seven days, which may push out your departure date. It's a good idea to book with airlines and accommodation providers who offer some flexibility in case you have to change your plans, or purchase travel insurance that covers your for disruptions due to contracting COVID-19.

The good news is that after seven days the virus is no longer transmissible for the vast majority of people, and your odds improve again by day 10.

"By the time you've reached day 10, virtually everybody is no longer infectious," say Peter Wark, a conjoint professor at the University of Newcastle and member of the Vaccines Immunology Viruses and Asthma (VIVA) research group at Hunter Medical Research Institute.

Is it possible to test positive for COVID after I'm no longer symptomatic?

Yes, and it's not as rare as you think, according to Wark. In fact, the number of people testing positive for up to two weeks after a COVID diagnosis may be as high as 1-in-10.

"Around 10 per cent [of those with COVID-19] by day 14 will still be testing positive. If you go to day 30 it's about 1-2 per cent," Wark said.

Of course, this isn't very comforting for those with an overseas trip planned within 30 days of contracting the virus. In this instance, your risk of returning a result that's positive, or a false-positive (when you test positive but are no longer infectious), increases sharply.

A false-positive result occurs when a PCR test detects the presence of cells (viral ribonucleic acid, also known as RNA) that carry the genetic information of the virus, and which the virus uses to replicate.

"You only need a tiny, tiny amount of viral RNA to be present in order to detect it," Wark said.

Scientists make assumptions about a virus's infectious potential based on the levels of viral RNA someone has – and extremely low levels can indicate the virus is no longer capable of replicating or causing infection.

"You'll find that up to probably about day 14, about one in 10 people still actually come back as positive on their PCR test, but if you look very closely they have very, very low levels of viral RNA present."

Do I need a COVID recovery certificate before travelling overseas?

If you've recovered from COVID within the last 30 days you may still get an exemption to fly by providing a COVID recovery certificate from a medical practitioner at check-in (the certificate should note it's been seven days since a positive COVID result, and that you've not had symptoms for the last 72 hours, among other criteria). Qantas offers its own COVID-19 Past Positive Medical Clearance form for passengers and their doctors to fill out.

If I've had COVID recently, can I get it again overseas?

In short, yes. But your risk of reinfection hinges on myriad factors, such as: are you vaccinated? How long ago did you get COVID-19? What variant was it?

There is still a lot of uncertainty around the topic of reinfection, according to a spokesperson for the Department of Health.

"Given the emergence of the Omicron variant, the specific strength and duration of SARS-CoV-2 immunity is unclear and research is ongoing," the spokesperson said.

"The best method of protection against severe illness from COVID-19 is vaccination."

Wark said reinfections, particularly for different variants of COVID-19, are well documented now.

"We're seeing a number of reinfections. Particularly among those who had earlier strains of the virus such as Alpha and Delta, with some of the Omicron variants, particularly BA2," he said.

Depending on your state, if you're re-exposed to the virus within eight weeks of your last infection, you aren't required to get tested or isolate, though more research needs to be done.