Lockdown measures designed to stop the spread of the coronavirus in Australia seem to also be suppressing the country’s flu season.
Australia’s flu season normally peaks during its winter months, from June to August. But cases often start to build around January, as travellers from the northern hemisphere bring the virus into the country.
This year, Australia began with relatively high flu rates: it had 6962 laboratory-confirmed flu cases in January and 7161 in February. However, cases have since nosedived, with 5884 recorded in March and only 229 in April, compared with 18,705 in April 2019. This is despite more flu testing being conducted this year.
Australia’s FluTracking surveillance system, which surveys about 70,000 people each week and records their flu-like symptoms, shows that, in the week ending 26 April, only 0.2 per cent of Australians had symptoms. This figure was 1.4 per cent at the same time last year.
Stopping the spread
The sharp reduction in cases is probably due to Australia’s decision to shut its borders on 20 March and ban non-essential gatherings to try to stop the spread of covid-19, says Robert Booy at the University of Sydney. “We’re not importing any flu and anything that stops close contact with others is going to make it harder for the influenza virus to transmit,” he says.
The government implemented a ban on non-essential gatherings of more than 500 people on 16 March. This gradually ramped up to a more complete lockdown on 23 March when pubs, restaurants, gyms, cinemas and other non-essential businesses were forced to close.
Additionally, very few children have been attending school since mid-March, when states and territories began encouraging remote learning where possible.
This is probably another reason why flu cases are down, since schoolchildren are known to be major spreaders of the influenza virus in normal years, says Kirsty Short at the University of Queensland.
Covid-19 lockdown measures also seem to have brought an early end to the flu season in Hong Kong, which normally extends to March or April, but this year tailed off in February.
Australia has seen a drop in covid-19 cases since its lockdown measures began, with 20 or fewer new cases being reported each day in the week ending 1 May. The government says it will decide whether to wind back social distancing measures on 8 May.
If strict measures to control covid-19 are kept in place, flu cases should continue to be suppressed, says Booy. “That could mean we see fewer deaths from respiratory infections overall this year,” he says. Covid-19 deaths in Australia have been relatively low at 92 so far, while between 1500 and 3000 Australians die of influenza in a normal year.
But even if the restrictions are eased, we could still see a reduction in flu cases due to changes in people’s behaviour, says Short. “People are washing their hands more and instead of having the attitude that they can still go to work if they’re sick, they now know to stay home if they have respiratory symptoms,” she says.
More Australians than usual have been vaccinated against flu this year, which may bring cases down as well, says Short. But cases may rise again when Australian students return to classroom learning, which is scheduled to happen at different times across the country, she says.
“Fortunately, it doesn’t seem like covid-19 is transmitted by schoolkids, but we know that children are a hotbed of influenza infection,” says Short. “It will be really interesting to see what happens.”
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