Countries have been urged to recommend masks on long-haul flights as the latest COVID-19 subvariant continues to spread rapidly in the United States, according to the World Health Organization (WHO).
The XBB.1.5 Omicron subvariant has so far been detected in more than 25 countries, including eight cases in Australia.
Labelled by the WHO as the most transmissible Omicron subvariant so far, XBB.1.5 accounted for 27.6 per cent of new COVID-19 cases in the US last week, according to health officials.
The subvariant now accounts for more than 40 per cent of all US cases, according to the Centres for Disease Control and Prevention.
Passengers should be advised to wear masks in high-risk settings such as long-haul flights, said the WHO's senior emergency officer for Europe, Catherine Smallwood.
"This should be a recommendation issued to passengers arriving from anywhere where there is widespread COVID-19 transmission," she said.
Australia scrapped its mask mandate on domestic and international flights on September 9, 2022, with travellers only "encouraged" to wear a mask to decrease their personal risk.
Health Minister Mark Butler said at the time: "[The mandate] has been removed on the advice of the Chief Medical Officer that it is no longer proportionate in the current context.
"I encourage everyone travelling overseas to be mindful of the continuing risk of COVID-19 and to take personal precautions to stop the spread and stay safe."
Experts say it is unclear if XBB.1.5 will cause its own wave of global infections.
Current vaccines continue to protect against severe symptoms, hospitalisation and death.
"Countries need to look at the evidence base for pre-departure testing," Ms Smallwood said, adding if action was considered, "travel measures should be implemented in a non-discriminatory manner".
That did not mean the agency was recommending testing for passengers from the United States at this stage, she added.
XBB variants 'less severe' than predecessors
XBB.1.5 is another descendant of Omicron, the most contagious and now globally dominant variant of the virus that causes COVID-19.
It is an offshoot of XBB, first detected in October, itself a recombinant of two other Omicron subvariants.
Asked about the XBB variant in November, Mr Butler called it "substantially less severe".
"They're all part of the Omicron family and have sort of similar traits in the sense they're quite infectious, they're much better than previous variants at evading immunity," he said.
"If you've had vaccination, that's not a rock-solid guarantee you're not going to get it. If you've had an infection before, it's not a rock-solid guarantee you're not going to get it.
"But like the other variants we've seen over the course of this year, they're substantially less severe than the earlier variants, like the Delta variant that hit Melbourne and Sydney very hard last year.
"This is a bit different to the previous waves in the sense we've got what people are describing as a bit of a variant soup."
Masks are already being recommended for people flying into the European Union from China, where COVID case numbers have exploded after the country scrapped its controversial zero-COVID strategy.
According to data reported by the WHO earlier this month, analysis by the Chinese Center for Disease Control and Prevention showed Omicron subvariants BA.5.2 and BF.7 were the most common in China.
The European Union Aviation Safety Agency (EASA) and the European Centre for Disease Prevention and Control (ECDC) said airlines should take "non-pharmaceutical measures" to reduce the spread of the virus on flights from China, including mask-wearing and pre-flight tests.
The agencies said "random testing may also be carried out on a sample of arriving passengers", as well as "enhanced cleaning and disinfection of aircraft serving these routes."
Last week, the EU's Integrated Political Crisis Response group (IPCR) also recommended all passengers on flights to and from China should wear face masks.
ABC/Reuters
