Hospitals across Australia particularly in the hardest hit State of New South Wales have been busy this winter and spring, as the number of flu cases has increased by more than 150 percent year on year.

Health officials are blaming it on a mutant strain of influenza, which is thought to be responsible for more than 370 deaths, and sickened more than 160,000 others so far, even though it was included in this year’s flu vaccine.

They estimate that up to 85 percent of the people that received a flu shot this year are still contracted with the disease.

Researchers said one possible reason is that this strain continued to mutate after the vaccine was developed.

While the elderly and young children are usually at risk, other age groups, including relatively healthy people, are also in danger.

Health officials fear the number of cases is much higher because of a delay in reporting.

( Nina Bascon / UNTV Correspondent )

Tags: Australia, kills hundreds, worst flu