The 2020 influenza season has seen a significant overall decrease in flu cases due to coronavirus measures, down to historically low levels; however as the vast majority of symptomatic individuals don’t get tested, the data we have may underestimate flu activity1.
Last year we endured very high levels of flu activity compared to previous seasons², and those levels were high from earlier in the year – even during the summer months, culminating in more than 310,000 laboratory-confirmed flu notifications by the beginning of December2. By comparison, there have been only 20,823 confirmed cases of influenza this year (to July 13), a massive 93% drop compared to 20193.
2019: 313,061 Laboratory-confirmed notifications of influenza in Australia for the calendar year.
To download a PDF of the graph “Annual Australian influenza statistics” click on the graph below.
The flu season normally peaks in Australia during our winter months, from June to August, however cases often start to build around January with travellers returning from the northern hemisphere’s winter season⁴. This year however, lockdown measures intended to decrease the spread of the novel coronavirus in Australia have had the added effect of suppressing the country’s flu season.
According to Prof Robert Booy, Head of Clinical Research at the National Centre for Immunisation Research and Surveillance (NCIRS), if strict covid-19 measures are kept in place, flu cases should continue to be suppressed⁴. “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 said.
So the downward trend in influenza infections this season may in part depend on whether the positive changes in people’s behaviour will continue despite the lifting of restrictions in recent weeks4. While we hope that this is the case, we have already seen a slight increase in respondents reporting influenza-like symptoms with the easing of social distancing measures in the latest FluTracking survey5.
One important factor in our favour for keeping our flu numbers down is that more Australians have received the annual influenza vaccine this year4. Recent evidence suggests optimal protection occurs in the 3–4 months following vaccination, with experts usually recommending vaccinations from mid-April or May 2020, but it is never too late to be vaccinated6.
Lastly, does this mean that we are in for a rebound season in 2021? According to Professor Ian Barr, Deputy Director of the WHO Collaborating Centre for Reference and Research on Influenza at the Doherty Institute, the flu is “very unpredictable” and the severity of the season is dependent on a number of factors. “What we don’t really know is how much impact there really is with having low seasons in terms of exposing people in one year or not exposing them, and then having them more susceptible the following year”, Prof Barr said.