Doctors in Britain are bracing themselves for an outbreak of flu in the next few weeks that could match Australia’s recent epidemic – one of the worst for a decade.

At least 170,000 cases were confirmed at the end of the Australian winter, more than twice as many as in 2016. Federal health officials say they logged 72 flu-related deaths among this year’s total.

“We know that the virus responsible for a large number of those cases was a strain of the H3N2 influenza virus,” says Prof Andrew Easton, of Warwick University.

“A similar viral strain was used to create part of the vaccine that has been distributed round Britain this month. However, we do not know how well it will work until this year’s flu epidemic begins.”

The flu outbreak that struck Australia and New Zealand was not particularly severe in individual terms. Most deaths occurred among the elderly, as is often the case with influenza.

One of the worst outbreaks occurred at a single nursing home, St John’s Retirement Village in Wangaratta in Victoria’s north-east. A total of seven elderly people died.

However, the sheer number of cases triggered during the outbreak was unexpected.

“We are still not sure why so many cases occurred this year in Australia,” added Easton. “It may have been that surveillance in some areas was better than it had been in the past. This could have produced an apparent increase in numbers of cases.

“Or it could be that there was something different, in terms of virulence, with the H3N2 strain that affected Australia. We should certainly be cautious.”

Prof John Oxford, of Queen Mary University of London, said: “It would be common sense to be pre-armed and to be as proactive as we can in preparing to protect ourselves from this year’s flu outbreak.”

The main unknown is the efficacy of the vaccine that is now being administered in the UK.

Every year the World Health Organisation reviews the main strains of influenza in circulation globally and recommends which of these should be used as the targets for the following season’s vaccine programme.

These strains were selected nine months ago, before the Australian outbreak occurred.

“We know historically that flu vaccines are usually 40% to 60% effective,’ said Richard Pebody of Public Health England.

“That means that having the vaccine will reduce your risk of getting flu by 40 to 60% compared with those not getting the vaccine.

“Children aged two to eight, health care workers, and those over 65 should therefore take the vaccine.”