A leading infectious expert on Monday warned that Australia could face a flu epidemic as it opens its international borders.

The report by Sheena Sullivan from the University of Melbourne, which was published in the Medical Journal of Australia (MJA), showed that strict public health measures targeting Covid-19 have effectively eliminated all local transmission of influenza strains in Australia over the last 19 months, reports Xinhua news agency.

“As the influenza incubation period, infectious period, and serial interval are short, the current duration of hotel quarantine (14 days) has prevented people (from) leaving quarantine while still infectious,” wrote Sullivan.

In 2017, Australia experienced a particularly severe flu season. Data from the Australian Bureau of Statistics showed that over the year more than 250,000 people contracted the strain and 1,255 died.

However this year to November, just 598 cases and zero deaths have been recorded, according to a report from the Department of Health.

Now, as Australia gradually reopens to the rest of the world, Sheena said there is a looming threat of an “out-of-season” flu outbreak.

“The main thing to say is that just because it’s not winter, we shouldn’t expect not to see a flu epidemic,” she told Xinhua.

She said common flu may pose more of a threat due to Australians’ lack of exposure to new strains and a drop-off in flu vaccination rates over the last two years.

She suggested particular attention would need to be paid to how entering strains affect different age groups, for example, the respiratory syncytial virus (RSV), which in adults shows minimal symptoms but leads to high hospitalisation rates in young kids.

“During outbreaks of RSV, there were much higher than expected rates of hospitalisation in very young children, and that was in the summertime.”

She believed, however, that many health measures adopted by the public during the Covid-19 pandemic could prompt a cultural shift in Australia, such as mask wearing and social distancing, that would help prevent infectious disease transmission in the future.

She said capacity for testing developed during the pandemic could also serve as an early warning system for problematic flu outbreaks.

“When we start seeing these signals of increased activity for these other viruses… hospitals can be in a bit more heightened awareness about testing.”