The three elderly victims, aged 81, 94 and 103, were all residents of the Royal Freemasons' Monash Gardens residential care centre.

The Immunisation Coalition has recorded 71,256 laboratory-confirmed cases of the flu this year, and says 2017 has the potential to be the biggest flu season on record.

There are four different strains of the virus circulating this year, the Immunisation Coalition said.

The Department of Health said the nursing home notified authorities of a flu outbreak on July 11.

The highly-contagious virus infected 38 people at the facility, including staff.

The three people who died all had serious underlying health conditions, a department spokesman said.

Influenza is a serious threat to nursing homes, and outbreaks are not uncommon, said Kim Sampson, chief executive of the Immunisation Coalition.

Old age naturally weakens the immune system and the flu vaccine is less-effective in the elderly because their immune systems weaken with age.

"We know that between 1500 and 3000 people die each year from flu-related illnesses, and most of those people will be the elderly. It is by far the elderly that are ones that we lose," he said.

Nursing homes typically administer antiviral medication to residents during flu season to stop any virus that enters the population spreading, as well as requiring all residents and staff to be vaccinated.

But it is often visitors and family members who bring the virus in with them, Mr Sampson said.

The Department of Health spokesman said the Royal Freemasons' care centre managed the outbreak according to the correct guidelines.

"I don't think there is any blame that can be attributed here. We're talking about people who are elderly and have serious underlying conditions," he said.

Royal Freemasons has been contacted for comment.