The flu epidemic has struck the entire mainland US at the same time and in similar levels for the first time ever as health officials warn the season could get worse.

Influenza activity is now widespread in all states except Hawaii with the deadly virus already claiming the lives of more than 85 adults and 20 children this flu season.

The US Centers for Disease Control and Prevention has reported that two strains of influenza viruses are being reported across the country, including H3N2 and H1N1.

'This is a bad flu season,' said Dr Dan Jernigan, the director of the CDC's influenza branch.