If you’ve escaped flu this year, there’s some good news: the peak of our bad flu season seems to have passed in most, if not all, parts of Australia.
But because there have been significantly more influenza cases than usual, there’s still a lot of illness around.
We asked infectious diseases experts Professor Peter Collignon from the Australian National University’s Medical School, and Professor Allen Cheng from Monash University and The Alfred Hospital to answer some common questions.
How bad has this year’s flu season been?
If you look at the result of lab tests, there’s been more than 2.5 times the number of confirmed cases of influenza compared to last year, Professor Collignon says.
But this figure is misleading because some of the rise is due to an increase in the availability of rapid testing for flu.
The number of hospital and GP visits for influenza is a much better guide and these suggest about a 50 per cent rise in flu cases, he says.
But it’s hard to say for sure until the flu season is over and all the data is collated.
Professor Cheng estimates in total, about 5 per cent of Australians will have had flu this year.
The total number of flu deaths is not yet known.
Figures collected by ABC 7.30 last week showed there had been more than 370 confirmed influenza deaths recorded in four states so far. Many of these were in aged care facilities.
Why has it been a bad flu season?
A key factor seems to be that the flu vaccine has been less effective than expected this year.
Preliminary data suggests it offered only 15 to 20 per cent protection, Professor Collignon says.
This means as many as 85 per cent of people who were vaccinated and then exposed to the virus still got infected.
“For whatever reason, the vaccine has been very ineffective this year.”
One reason for this is the influenza virus can mutate rapidly.
Because the vaccine has to be planned and manufactured many months ahead of the start of the flu season, the strains on which the vaccine are based may end up not being a good match with the strains of flu virus circulating.
“A lot of seasons there’s a mismatch. But even if there isn’t, the vaccine often just isn’t as effective as you’d expect it to be. We don’t know why,” Professor Collignon said.
“We really need a better vaccine. We need a different design of vaccine that … gives us protection for the next five or 10 years, no matter what strains come.”