A simple GP's letter has plunged more than 40 people in the borough into an excruciating world of waiting.

They are among 205 patients being screened nationwide for the hepatitis B virus after undergoing treatment at the Finchley Alternative Medical Centre in Ballards Lane, Finchley.

With the number of confirmed cases rising this week to 16, about one in seven tests is currently coming back positive.

"Some individuals appear to be at the very early stage of the infection," said Professor Geoffrey Dusheiko, Professor of Medicine at the Royal Free Hospital, who will treat most of the patients from Barnet involved in the outbreak.

"We have a responsibility to tell them that there are new drugs for hepatitis B which are not licensed yet and could be used to treat these patients."

Such drugs have been used already in trials to treat chronic hepatitis, but Prof Dusheiko believes they could also help in the earliest stages of the illness.

But first, patients must be made aware of the risks involved in any new drug. "We would say to the patients that it might be possible to treat you at this very early stage with new drugs," said Prof Dusheiko.

"But it might mean watching patients very closely for three to four months first. If we were to treat too early before you had developed an immune response some would be left with residual hepatitis and there would be a reaction."

Like HIV, hepatitis B can be spread from mothers to unborn children by sharing dirty needles and through unprotected sex.

It means that the outbreak could have already spread beyond the 205 people traced directly using the medical records at the private Finchley clinic.

"Not until we have all the individuals who have been exposed to the virus and processed this information can we know how many other people have been exposed. We hope that most individuals are in monogamous relationships.

"We will be asking them fairly direct questions and screening them with a view to contacting their sexual contacts.

"To date there is no data to suggest that this outbreak also involved HIV although there is some question about hepatitis C."

Those undergoing tests will have to wait weeks before they get answers to all these tests.

Hepatitis factfile

o hepatitis B outbreaks are rare and the present one is likely to be one of the biggest in the UK in 50 years.

o symptoms take about three months to appear. The most frequent complaints are tiredness, fatigue, flu-like symptoms, weakness, loss of appetite and abdominal pains.

o about half of adult cases develop immunity without apparent symptoms. The rest may develop jaundice and require a few weeks bed rest.

o up to five per cent of adult patients develop a long-lasting (chronic) infection and do not get rid of the virus. Fewer may suffer life-threatening liver damage.

o blood tests will be used to determine what stage the infection has reached. Some patients will already be developing immunity while others may not yet have developed symptoms.

o the body's immune system is the most effective weapon against the virus. Bed rest and a nutritious diet aid recovery.

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