Australia has entered a fourth COVID-19 wave of infections with surging case numbers prompting renewed health warnings.
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NSW and Victorian chief health officers have warned communities to remain vigilant, however there are currently no COVID-19 public health measures in place around Australia.
Why are cases rising again?
COVID-19 infection numbers are on the rise again around Australia in part because of the Omicron subvariants BQ.1 and XBB that are tipped to become dominant variants throughout Australia.
The Victorian Department of Health said the ability of XBB and BQ.1 to escape immunity from past infection, combined with waning immunity from past vaccination, was driving rising cases in Australia and overseas.
Deakin University chair in epidemiology Professor Catherine Bennett told ACM this was the first time Australia had a mix of infection variants present in the community at the same time.
"In the past, we've had waves that have just been one particular variant. So now we have variants that are a bit different to ones we've seen before, meaning everyone's a bit susceptible to them," she said.
Even if you get an infection with one of them, you could be exposed to another [one] as you recover.
- Professor Catherine Bennett
Last week a hospital ward in Perth's south shut down after a COVID-19 outbreak.
The small outbreak comes as WA COVID-19 numbers have nearly doubled in just over a month.
New cases have jumped by 63 per cent in Victoria from 10,226 to 16,636, while weekly infections in NSW have risen by more than 7,000.
Queensland moved its traffic light COVID-19 advisory system up a level from green to amber, advising residents to be alert.
Queenslanders have also been encouraged to wear face masks on public transport and in hospitals and aged care homes.
Professor Bennett said that while public health measures are now difficult to enforce, good public health communication remains important to help people minimise their personal risk.
"I call it the pollen-count equivalent. If you have allergies, you know what to do when it's a high pollen-count day. You don't go outdoors, you keep your windows closed, put your air conditioning on recycle, et cetera, you take your antihistamine in the morning," she said.
"It's the same with COVID. If you know that things are shifting and that now your exposure risk is going up then you decide to get your groceries home delivered if you can, or you choose to sit outside of the café rather than the inside."
Across the nation the number of COVID-19 patients in hospital has increased by an average of 11.6 per cent compared to the last week.
In Sydney, hundreds of COVID-positive passengers disembarked the Majestic Princess cruise ship, recalling the Ruby Princess superspreading incident of 2020. An official inquiry found the total number of deaths associated with the ship was 28 and the number of infections was estimated at no fewer than 900.
Around 800 of the 3,300 passengers aboard the Majestic Princess cruise were COVID-positive.
How does Australia compare to other countries?
Like most countries, Australia has wound back public health measures, opened borders, and scrapped mandatory isolation.
Australia has a world-class rate of vaccine uptake, 97.2 per cent of people over 16 have had at least one COVID vaccine dose.
However, Victorian chief heath officer Brett Sutton said increasing hospitalisations has been driven by the Omicron subvariants BQ.1 and XBB.
In Singapore, it only took three weeks for XBB to overtake every other variant in the island country.
According to Singaporean government data, there has been no evidence of these subvariants causing more severe illness than previous variants. In good news, XBB was estimated to have a 30 per cent lower risk of hospitalisation compared to Omicron BA.5 variant cases.
Professor Bennett confirmed that overseas examples should reassure the Australian public.
"When this has happened overseas, the wave has tended to be less impactful than previous waves, certainly nothing like BA1 at the start of the year," Professor Bennett said.
"And they haven't seen as many people hospitalised with it or becoming seriously ill. So just like the other variants, we've got to be careful with it."
In the UK, Europe and North America, the prevalence of BQ.1 is rising quickly.
Recent data from the UK's Office for National Statistics estimated BQ.1 sub-lineages (including BQ.1 and the similar BQ.1.1) made up 16.7 per cent of infections. In the US, BQ.1 and BQ.1.1 together make up around 35 per cent of infections.
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What are the rules if you have COVID?
Most Australians are no longer required to isolate or report their positive test result if they are infected with COVID.
Professor Bennett stressed the importance of having a third shot booster dose to protect yourself over the Christmas season.
"We know from health department reports that people who aren't vaccinated or aren't fully vaccinated are still over-represented in those that end up in hospital," she said.
"And if people have actually had quite a few infections and think, Oh, why bother? Actually, not having another infection for a while might be a good thing, and might help keep them free of long COVID, for example, because we don't know how much repeat infections might alter your risk."
All states and territories still encourage anyone with a positive RAT result to stay home until symptoms have subsided, and wear a mask if travelling while infectious.
In all states, if you test positive for COVID-19, you must not visit high-risk settings like aged and disability care facilities and hospitals, unless seeking immediate medical care, until at least seven days after testing positive and symptoms have disappeared.
In the ACT and South Australia positive RAT results must be registered with the Department of Health. Reporting test results is strongly encouraged in all other states.
