Brain samples were tested

But the contents of the paper were astonishing. In it was a potential solution to what has been called the biggest medical mystery of all time.

Two young doctors had tracked down the probable cause of one of the most baffling epidemics of the 20th Century - a disease called Encephalitis Lethargica.

Encephalitis Lethargica was a devastating illness that swept the world in the 1920's.

It attacked the brain, leaving victims like living statues, speechless and motionless.

During the outbreak, nearly a million died, and millions more were left frozen inside their useless bodies, in institutions.

No-one knew what had caused it, or how to treat it.

Reppearance

For virologist Professor John Oxford, the disease was not just a disease of the past. As an expert on the condition, he was convinced that it could reappear.

Professor Oxford could not find the cause

And in 1993, it seemed his fears were being realised.

Becky Howells was 23 years old, when she suddenly became very ill. She started shaking, becoming feverish, hallucinating.

Within hours she had become critically ill and was rushed to hospital. Doctors had no idea what was wrong.

They knew her brain was dangerously inflamed, but had no idea what was causing it.

Her doctor Stavia Blunt said: "I was shocked by her appearance, stunned. She had these very bizarre clawing movements of her arms. It was weird."

Her father Tom prepared himself for the worst.

"I said goodbye. I said goodbye at the resuscitation unit, because I didn't think I'd see her again," he said.

Astonishing conclusion

As doctors battled to save her life they were forced to an incredible conclusion.

Becky was suffering from Encephalitis Lethargica - a disease that had last appeared over 70 years before. And it was just as baffling now as it was then.

Professor Oxford was convinced that the solution lay in the past. He tracked down brain tissue samples from the original 1920 victims and tested them, looking for traces of a virus that could have been responsible for the outbreak all those years ago.

At the time, an unusually severe strain of influenza, Spanish flu, had swept the world, and it seemed possible that both epidemics were linked.

But despite exhaustive testing with the latest molecular probes, there was no evidence of any virus - flu or anything else.

Becky gradually recovered, but it was two years before she could restart her life.

More cases

And Becky was not an isolated case. Since then more and more patients have been discovered. All suffering from the same bizarre symptoms.

Patricia Vaughan, was an energetic, active woman when she was struck down with the mysterious illness four years ago.

Sadly, she did not make a full recovery and now needs full time care from her partner, Geoff Shillington.

"It's very hard, because no-one can help you and you're just sitting there watching somebody going downhill, and you can't do a thing about it," he said.

At Great Ormond Street Hospital, one young doctor, Dr Russell Dale was alarmed that the disease was more common than he had ever realised.

He started tracking down other similar cases. Word got round the medical community and colleagues began referring their own cases to him.

Gradually he build up a case load of over 20 patients - all with Encephalitis lethargica.

At this stage, the disease was still a complete mystery. Noone had any idea what might be causing it - or, more worryingly, how to treat it.

Analysis

Together with a colleague, Dr Andrew Church, the two doctors began analysing all their patients to see if they had anything in common.

We realised we must be onto something

Dr Andrew Church

So the two doctors started looking for evidence of bacterial infection - and particularly streptococcus bacteria which is a common cause of sore throats.

"It was amazing really and very exciting, when the first results came back," said Dr Church.

"We got first one, then two, then ten...then all the patients had the same result. So we realised we must be onto something."

They had discovered evidence of a rare form of streptococcus bacteria in all their patients.

The bacteria that can cause a simple sore throat had mutated into a much more severe form and triggered the attacks of encaphilitis lethargica.

Immune reaction

It seems that in some people the body has a massive immune reaction to the streptococcus bacteria and then turns on the body itself; attacking the brain and destroying it.

It was an astonishing discovery. But that was not the full story.

Dr Church as keen to see if there was any evidence to suggest that this might also have been the cause of the 1920 epidemic all those years ago.

Dr Dale went back to the original medical records of the time. And as he pored over the reports, he discovered two very telling pieces of evidence.

First, many of the original victims had also presented with sore throats, and secondly, in the detail was a reference to a particular bacteria - diplococcus. Diplococcus is a form of streptococcus bacteria.

It was astonishing. There in the medical records was a description of a bacterial infection very similar to the one causing the modern cases of Encephalitis Lethargica.

For Dr Dale and Dr Church it was a very exciting moment. Not only had they identified the cause of the modern cases, they may have finally cracked an 80-year-old medical mystery.