As the mercury drops and days get shorter, sniffles, sore throat and other classic symptoms of flu typically start rearing their snotty, grotty heads.
But this winter, we're looking down the barrel of an unusual flu season.
Right now, we have the more contagious BA.2 COVID sub-variant sweeping across the nation, since reaching our shores in January.
Over the past couple of years, COVID restrictions and border closures crushed influenza infections to historic lows.
Last year, researchers thought one flu virus called the Yamagata virus might even be stamped out altogether (and, in the months since that article was published, there have been no further reported cases of Yamagata).
But just because the flu's been noticeably absent over the past couple of years, doesn't mean it won't pose a real problem for us this year.
For this reason, in March, the Australian government announced it would provide a $2.1 billion health package to tackle the problem of flu and COVID this winter.
So why all the kerfuffle about influenza now, and what's changed since last winter when it comes to COVID, flu, and vaccination?
Why are we especially vulnerable to flu this year?
We're vulnerable simply because we've had so few flu infections in 2021 (and that's despite only about a third of people getting a flu shot last year).
The reason for historic low flu levels is because the virus, in non-pandemic years, hitches a ride on incoming passengers from overseas.
But with international borders closed for the best part of the past two years, and the trickle of arrivals spending two weeks in quarantine, any inbound flu viruses were essentially stopped before they could take hold in the wider population.
With a fraction of the usual flu infections, there aren't too many people today who have immune protection generated from catching the virus.
Now, with borders open and quarantine rules relaxed, it's inevitable that flu will spread — and we're already beginning to see it, said Ian Barr, deputy director of the World Health Organization's Collaborating Centre for Reference and Research on Influenza at the Doherty Institute.
According to the National Notifiable Disease Surveillance System, which keeps tabs on lab-confirmed influenza case numbers, Australia racked up 409 cases in March — most of which were in Victoria and NSW.
"And that was nearly the equivalent of the total for 2021, which was 598 cases," Professor Barr said.
"So things are picking up and there will be higher numbers in April. So we're already off to a bit of a flying start."
What can we learn from the Northern Hemisphere flu season?
The Northern Hemisphere has not long emerged from winter. So how did they fare when it came to flu?
As you might expect, different regions experienced different flu seasons, likely due to different levels of restrictions like mask-wearing and border closures.
In the US, the Centers for Disease Control and Prevention reports the hospitalisation rate for the 2021/22 flu season is lower than the rate at this time of year for the four years preceding the pandemic.
But what's unusual about this US flu season is it hasn't followed the typical pattern of a rise, peak, then fall in cases.
Instead, it looks like the US season will have two peaks. After the first peak in 2021, another wave is picking up again now.
The reason for this isn't entirely clear, but Professor Barr suspects US flu cases are rising and falling due to people changing behaviour during and between COVID outbreaks.
"If COVID goes up, people stay home more often, and there's less mixing. Some US states have more rigid rules on mask-wearing and school closures, so probably all those things come into account to stop influenza.
Relatively low overall flu numbers abroad are a reason for cautious optimism for Australia as the weather cools.
"It's a hard thing to predict, but I think it's likely we'll have a low-to-moderate season rather than a severe season," Professor Barr said.
"But once enough of these viruses get in, it could take off. "
Who should get a flu shot?
Vaccination is crucial if we're to keep a lid on flu numbers this year.
The reason we need a flu shot every year is because influenza is a shape-shifter; it mutates readily, creating new viruses that we have no immune protection against.
So the vaccine is tweaked to protect us against specific members of the flu-virus family, selected for inclusion, for instance, if they spread overseas.
In Australia, anyone over the age of 6 months is recommended to have a yearly seasonal flu vaccine.
Certain groups are strongly recommended to be vaccinated.
These are:
- infants and children aged 6 months to 5 years
- adults aged 65+
- Aboriginal and Torres Strait Islander people over 6 months
- anyone aged 6 months or over who has a medical condition, such as diabetes or cardiac disease, that means they are at higher risk of getting serious flu disease and complications
- travellers
- workers in settings such as healthcare, aged care, and poultry and pork industries
- people who are homeless
- people who are pregnant
Even without COVID circulating, anyone in these groups is at greater risk of complications and severe illness if they catch the flu.
For instance, pregnant women at any stage of their pregnancy are strongly encouraged to get a flu shot, says Megan Rees, head of the Royal Melbourne Hospital's Sleep and Respiratory Unit.
"We saw terrible swine flu in 2009, and we had lots of pregnant women really severely unwell with influenza."
When should I get my flu shot?
It's around this time of year that flu shots are rolled out in Australia, and that's no accident.
Antibodies generated by the flu shot tend to wane a little after about four months, but still provide "very solid protection for at least six months, probably a bit more than that", Dr Rees said.
So when our flu season peaks, which is usually in August, we are already protected. And should the flu season come early, we're ready for that too.
But this, as we know, isn't a normal flu season. So when will it peak?
That's a difficult question at the best of times, Dr Rees said.
"So our recommendation would be to get your flu vaccine as soon as possible, and you will be well protected for August and September, even if you got your flu vaccine now."
While the effectiveness of flu vaccines isn't as high as we've seen with the mRNA COVID vaccines, they do help stop the disease spread and, should you be infected by a flu virus, stop you from getting as sick.
And, of course, a flu vaccine (plus COVID vaccines) will decrease your risk of being co-infected with COVID. And that's important because ...
Is being infected with COVID and influenza particularly bad?
We're yet to see widespread influenza and COVID-19 at the same time in Australia, and overseas data puts flu co-infection at less than 1 per cent of COVID infections (although estimates vary by region).
But patients with the flu/COVID combo — dubbed "flurona" — are likely to appear as rules and restrictions continue to relax, and this has Dr Rees worried.
Recently, a study of more than 200,000 people in the UK found patients with COVID and flu had twice the risk of dying than people infected with the COVID virus alone, echoing conclusions drawn by previous studies.
For this reason, some hospitals, including the Royal Melbourne, already routinely test all patients with respiratory symptoms for both flu and COVID, Dr Rees said.
A flu test is similar to a COVID test: a nose and throat swab, which is sent to a lab for analysis.
Why can I now get a COVID vaccine and flu shot at the same time?
Last year, the Australian Technical Advisory Group on Immunisation (ATAGI) recommended spacing out your COVID and flu vaccines by two weeks.
They've since done away with that advice, and people are now encouraged to get both at the same time.
So what changed?
That 14-day break between COVID and flu shots was mostly a precaution in case people had a reaction to either vaccine, Professor Barr said.
Spacing them out meant it was easier to attribute any side effects to one vaccine or the other.
"Now we know only a small proportion of people have significant side effects from the COVID vaccine, and we know that [vaccine] co-administration is safe," Professor Barr said.
"There's very little risk [of side effects] with standard vaccinations, COVID or otherwise, with influenza vaccine."
There's another benefit to having both shots in the same sitting, Dr Rees said.
"You get it done. If you have to come back on separate occasions, sometimes people don't get the second one."
