America is set to endure one of the most perilous flu seasons in years - with doctors warning it could be similar to the deadly 2014 outbreak.

It is becoming increasingly clear that the US will be hit by a particular strain of influenza called H3N2, the same strain which has just wreaked havoc in Australia, and was responsible for the four most deadly flu seasons in the last 10 years.

Early assessments suggest the current vaccine - which was produced in spring after scientists made an educated guess at what strain to expect - will be just 10 percent effective.

While some seasons don't kick off until February, we are already seeing a surge in people hospitalized with influenza-like symptoms - at a rate even faster and earlier than we saw in 2014.

'I'm anticipating this being a bad flu year,' infectious diseases specialist Dr Pritish Tosh, of the Mayo Clinic, told Daily Mail Online.

Data from the CDC's interactive flu-tracking site (pictured) show cases of people falling ill with 'influenza-like illnesses' (ILI) are more widespread than in previous years

'Reports from other developed countries suggest suboptimal vaccine efficacy and we are still waiting to see which strain will predominate in the US. But I'm expecting it to be H3N2.'

The four most deadly flu seasons of the last 10 years — in the winters of 2003-2004, 2007-2008, 2012-2013, and 2014-15 — were H3N2 seasons, each with a particular version of that flu type.

Although H3N2 is not as virulent as some other strains of flu, it mutates very easily, making it stronger against the body's immune system.

In 2014, 147 children died of flu - most of them from a particular strain, H3N2. By the end of the year, the CDC declared an epidemic, with more than 20 deaths in just a few weeks before Christmas that year. As health officials rushed to contain the outbreak, the CDC admitted that the 2014 flu vaccine did not protect well against H3N2 - it had just seven percent chance of protection.

This year may not be so different.

'The predominant strain appears to be the H3N2 strain. Those tend to result in more severe epidemics,' Dr Tosh explains.

'Some of the early assessments of the vaccine from the Australia epidemic in their winter, our summer, suggest about a 10 percent vaccine efficacy which would then mean it was 10 percent effective in preventing the disease.'

He cautions that those figures don't take into account how much the vaccine helps to lessen the severity in those who do get sick.

But 'it looks bad'.

'We are seeing increased activity at this time although we are nowhere near its peak.'

The flu season is declared under-way once we have reached an above-average number of people with influenza symptoms (i.e. more than 2.2 percent of people). We surpassed that by Thanksgiving.

Data from the CDC's interactive flu-tracking site show cases of people falling ill with 'influenza-like illnesses' (ILI) are more widespread than in previous years.

Experts warn this could be an early sign that the US faces the same fate as Australia, which had one of its worst outbreaks on record, with two and a half times the normal number of cases.

Some of the country's hospitals had to resort to 'standing room only' after being hit by more than 100,000 cases of the H3N2 strain.

In 2014, 147 children died of flu - most of them from a particular strain, H3N2. Experts fear this season's flu could also be deadly and hard to control

Official figures are yet to confirm how many people have lost their lives to this year's outbreak, but 370 deaths have been reported so far.

Some infectious disease researchers are blaming the outdated methods for cultivating flu vaccines.

For more than 70 years, manufacturers have made the flu vaccine by injecting strains into chicken eggs.

This allows the virus to replicate. The fluid in the eggs is then purified to get enough of the virus to use in vaccines.

But flu viruses are constantly changing proteins on their surface to avoid being spotted, and the old technique is helping them.

According to the study, a strain of the H3N2 virus with a different outer layer protein emerged during the 2014-2015 flu season.

Last year's flu vaccine was updated to include the new version of this protein, but the egg-grown version had acquired a new mutation.

Researchers found antibodies elicited by the vaccine in ferrets and humans 'did a poor job of neutralizing H3N2 viruses that circulated last year'.

But a version of the jab produced without eggs allowed antibodies to 'recognize and neutralize the new H3N2 virus'.

'A lot more research needs to be done to get a vaccine that works every time for every season for everyone but I still encourage everyone to get it,' Dr Tosh insists.