Australia's leading influenza expert body on Monday urged citizens to book a flu shot now as the number of local people dying of flu keeps rising.

Up to 3,500 influenza-related deaths occur in Australia each year, which is higher than the national road death toll. Last year 18,000 Australians are hospitalized, the highest number to date.

The Influenza Specialist Group (ISG) said as of March, 4,381 flu cases had been recorded, compared to 3838 at the same time last year.

ISG chairman Alan Hampson said the most recent, serious influenza cases in the Northern hemisphere were caused by the A( H3N2) virus, which emerged as the predominant, circulating strain during the five-to-six month vaccine manufacturing period.

"The 2015 Southern Hemisphere free flu vaccine contains two new strains, including the H3N2 influenza strain, which has been responsible for a severe flu season and high flu hospitalization rates in the Northern Hemisphere, and the late outbreaks of influenza B in Europe," Hampsin said in a statement.

"All indications are that our vaccine is now a really good match for the coming Australian flu season."