Deaths from influenza and other respiratory infections in Australia have dropped significantly during the Covid-19 pandemic, according to new data.
The latest release of mortality data from the Australian Bureau of Statistics shows that two people died of the flu in July – the first deaths from the virus infection in Australia in a full year.
The numbers come as research from Doherty Institute researchers suggests that one of the four main types of influenza viruses that cause seasonal epidemics may be extinct due to Covid-19 health measures.
As of October 10, there have been only 550 cases of laboratory-confirmed influenza registered by the National Notifiable Diseases Surveillance System this year, with the Federal Ministry of Health noting that “activity in the community will remain at a historically low level by 2021”.
In the 2020 influenza season, there were just 21,266 laboratory-confirmed influenza cases compared to the previous year, where there were 313,033 influenza cases and 953 deaths.
In Australia, 1,276 deaths from all respiratory diseases were recorded in July, the most recent month for which figures are available. Modeling conducted by the Actuaries Institute, a professional body, predicted 1,600 deaths in the same period if the Covid pandemic had not occurred.
Jennifer Lang, chair of the Actuaries Institute’s working group on Covid, said pandemic-related public health measures were likely the cause of the decline.
“It is the fact that we have taken steps to avoid infection from Covid, which has helped us avoid being affected by a lot of other respiratory diseases,” she said.
“It’s impossible to be completely sure because this is one of the statistical things that could have just happened, but this has certainly been the lowest level of respiratory death in the time we’ve been looking at.”
Lang said flu cases have been down worldwide. “It’s been all the different measures that people take to avoid mixing, which has reduced the level of flu in circulation worldwide. Many health professionals are watching closely to see what happens when people start mixing again. “
A recent study led by Doherty Institute researchers, published in Nature Reviews Microbiology, has suggested that the “suppressive conditions of the Covid-19 pandemic” may have either severely suppressed or completely wiped out a line of influenza B virus.
Known as B / Yamagata, the genus is one of two that usually results in seasonal illness, but it has not been definitively discovered since April 2020.
The authors of the study noted that pandemic-related behavioral changes such as social distancing, mask wearing, and travel restrictions were important factors contributing to a global decline in the incidence of influenza.
Doherty Institute professor Ian Barr, co-author of another flu paper currently under review, said the eradication of B / Yamagata “may well reduce the amount of influenza B circulating”.
“We’ll probably have to wait at least another year before we can be sure it’s gone,” he said.
The northern hemisphere is preparing for the flu season
Barr, also deputy director of the World Health Organization’s Collaborating Center for Reference and Research on Influenza, said the closure of international borders has been a key cause of the decline in influenza cases throughout the pandemic.
He believes the easing of travel restrictions “will increase – certainly – the number of cases of influenza in the northern hemisphere in their coming winter”.
In the UK, the health service is aiming to vaccinate a record 35 million people with the seasonal flu vaccine – more than half of the country’s population – due to fears that the winter flu season could be particularly deadly.
It was difficult to determine how severe the next flu seasons – in both the northern and southern hemispheres – would be, Barr said.
In Australia, the reopening of international borders meant there was potential for out-of-season flu outbreaks, he added. Last summer, Australian hospitals noticed unusually high levels of respiratory syncytial virus in children.
“With the flu, we had a great year in 2019,” Barr said. “It started very early in the year – February or March – and so it’s an opportunity to happen again.”
Barr noted, however, that because influenza cases had fallen globally, it could also take time for infections to rise in Australia.
“People should consider flu vaccination in 2022, even if they did not get it in 2021 because of the increased risk.”
The four-component seasonal influenza vaccine selected for use in the Southern Hemisphere Influenza Season in 2022 will include B / Yamagata.
However, if the pedigree is truly extinct, influenza vaccines may in future be simplified down to three components to protect against two strains of influenza A and a pedigree of influenza B known as B / Victoria.
“It can make the virus faster and easier to make and cheaper,” Barr said.