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Seasonal flu ‘nowhere to be seen’ in Australia

Experts who have spent decades studying the seasonal flu in Australia have never seen anything like it. A virus once detected tens of thousands of times year is almost nowhere to be seen.

“It’s either eradicated, or it’s at such low levels we’re having trouble detecting it,” said the Doherty Institute’s Professor Ian Barr.

Influenza had already been pushed to record low levels in 2020, when just a few hundred cases were reported each month through winter after Australia shut its international border. But since then, cases have again dropped, almost to zero. In May, there were just 71 confirmed cases across the country, compared to more than 30,000 in the same month in 2019.

This disappearance of the flu wasn’t necessarily expected. It was thought that cases could resurge as most Australians began freely mingling again.

While experts say that is still a possibility — and there are some fresh warning signs it will — for now, the absence of cases is due to the fact they aren’t being imported from overseas. If they are, cases are petering out in quarantine.

The trend has had a strange impact on Professor Barr and his colleagues at the WHO Collaborating Centre for Reference and Research on Influenza in Melbourne.

Usually, the centre would have thousands of samples on hand to help them formulate the newest flu vaccine for the northern hemisphere in September (likewise, cases detected in the northern hemisphere are used to formulate the vaccines Australians are given).

But the few detections they are seeing now in Australia are either false positives, or they are from quarantine, mostly from Howard Springs.

“Normally, [the flu vaccine formulation] has a heavy bias on samples in the southern hemisphere. It will be quite difficult to make a judgment about what’s going to happen for that vaccine if we don’t get more samples in the southern hemisphere,” Professor Barr said.

Instead, the centre has been relying on samples they have accessed from other countries, including Cambodia and South Africa.

A similar trend has been reported by chairman of the Immunisation Coalition and GP, Rod Pearce, who helps undertake COVID-19 testing through a respiratory clinic in South Australia.

The testing doesn’t just pick up coronavirus, but another 10 viruses.

Dr Pearce said that until a month ago, the respiratory clinic testing wasn’t identifying any viruses at all. That changed in the past four weeks, and positive tests were now being returned in about one in a dozen cases, as the common cold (otherwise known as rhinovirus) made a return. Also coming through is the occasional respiratory syncytial virus, parainfluenza virus (which closely resembles the common cold) and adenoviruses.

“We are not seeing influenza at all, and I check all of them,” said Dr Pearce.

However he warned that the fact that other viruses were now circulating was “a great warning sign” that the flu could still come, and he urged people to seek a flu vaccine this season.

A few days ago, Australia’s vaccine advisory group changed its advice so it no longer recommended that people wait two weeks between having their COVID-19 and flu shots. It now says the preferred minimum interval is just a week and “in some situations a shorter interval (including co-administration) is acceptable”.

“One quiet year often leads to a rebound year, so we are at risk of that, and if people decrease their isolation and think they fine, the flu is just waiting to restart,” Dr Pearce said.

“And the flu is lethal, these other ones are just nuisances.”

There hasn’t been a single flu death reported in 2021, and there were less than 40 in 2020. This compares to more than 800 in 2019, a particularly bad season.

There were just nine cases of the flu confirmed in the first week of this month, according to the Immunisation Coalition. So far this year, there have been just 60 notifications of influenza in Victoria and 32 in NSW. Queensland has seen the most cases – at 171.

Meanwhile, there are 130 active cases of coronavirus in Australia.

University of Sydney infectious diseases expert Robert Booy said the flu had been also suppressed in other countries that had implemented lockdowns and social-distancing measures in response to coronavirus. But he says Australians should still expect a flu season this year, which he predicts will be mild to moderate and kick in around July or August.

“It’s not just COVID that sneaks out of quarantine, it’s flu as well,” Professor Booy said.

He also said lax social distancing was putting people at risk, as was a lower level of immunity in the community due to last year’s suppressed flu season.

Professor Barr suspects while restrictions on international arrivals remain unchanged, the flu will continue to be suppressed. Yet he also says it is not out of the question that there will be a delayed season.

“There are a lot of unknowns here. This is the first time seen numbers reduced to this level,” he said. “I’ve been vaccinated, so my philosophy is that it’s always better to be safe than sorry.”