Experts suggest that the quiet 2018 flu season may be a contributor to this year’s early surge, and that 2019 could surpass 2017’s bad season
The quiet 2018 flu season was remarkably different to the peak of 2017 – “in fact, a nadir,” according to Professor Robert Booy, chairman of the Immunisation Coalition.
Prof Booy, with experts including Professor William Rawlinson, Senior Medical Virologist, Director of Serology, Virology and OTDS Laboratories and NSW Health Pathology Randwick, who addressed an Australian Science Media Centre briefing this week.
“In 2018 we had a nadir, a very low season, and that makes me think about a century before, when we didn’t always have a flu season every winter. It only started, in 1918, to occur every year,” Prof Booy said.
“2019 has been really strange. There has been a sustained and rising summer and autumn surge that began at the end of last year, and it’s continuing to increase.
“It’s only an epidemiological, immunological guess, but the best explanation is that 2018 was so quiet that we have reduced community immunity. So there are more susceptibles… more people who are vulnerable to catching infection and therefore transmitting infection.”
Prof Booy said that the other major contributor to the big surge in the last few months has been the fact that both an A type H1 and H3 strain have been circulating, when it’s often only one strain which surges.
“The peak we have so far is nothing like the peak we had back in 2017, but that’s the risk we’re concerned about.
“There’s no sure way of predicting whether we’re going to keep having increasing numbers.”
He said the best time to get vaccinated was “now” as a May vaccination allows recipients immunity from flu which is currently circulating, and for about four months to cover the winter flu season.
Prof Booy urged health professionals to ensure that they are vaccinated against the flu this year.
“Herd immunity is attainable. You don’t need 95%, like with measles, to be vaccinated. If you have over 50% of the population vaccinated there will be at least some degree of herd immunity.”
This is something to aspire to, he said.
He also said that to date, the strains included in the 2019 flu vaccine were a “reasonable” match to the strains currently circulating, with no worryingly large amount of drift.
Prof Rawlinson told the briefing that in past busy flu seasons, there have been “in the order of a couple of million” flu cases per year, “although often we only see about a quarter or less of those actually measured because of the lack of reporting and the lack of laboratory testing”.
He predicted “a couple of million” cases this year, the highest number since 2017: “Although I’d be very concerned that it may be higher because we haven’t seen so much in 2018 and since”.
There have been a total of 39,128 laboratory confirmed notifications of Influenza in Australia for 2019, as of the start of 6 May.