A drug-resistant superbug which last year killed more than 5,000 hospital patients has "escaped" into the community and is believed to be infecting thousands of people.

A drug-resistant superbug which last year killed more than 5,000 hospital patients has "escaped" into the community and is believed to be infecting thousands of people.

Hospitals this week will start a £31m campaign to improve hygiene in an attempt to curb the spread of methicillinresistant staphylococcus (MRSA), which last year cost the NHS more than £1bn to treat. Last night, however, a government microbiologist, Dr Peder Nielsen, told the Independent on Sunday that MRSA was now at large outside hospitals.

Dr Nielsen, who is director of the Peterborough branch of the Public Health Service Laboratory, and a consultant microbiologist at Peterborough Hospitals trust, said 54 per cent of all new cases of MRSA were being picked up by GPs. He said there was now a "reservoir of infection" in the community that was "a threat to hospitals".

MRSA eats into the flesh of wounds or enters the body via medical equipment such as drips and catheters. In many cases surgery is required to remove infected tissue. The disease struck at least 10,100 people in the UK last year and killed more than 5,000.

Excessive use of antibiotics has led to the rise of MRSA, so named because of its resistance to methicillin. The bug is now impervious to a range of antibiotics and can only be treated with powerful lastline-of-defence drugs.

Cases in the Peterborough area rose from five in 1994 to 135 in 1998, according to Dr Nielsen. A quarter of these cases were in nursing homes where large groups of elderly people were grouped together. The remaining 75 per cent of cases were scattered across all ages and all parts of the community.

Although his study is Peterborough-based, Dr Nielsen said he had "no doubt whatsoever" that his findings would be replicated across the UK.

Dr Chris Butler, senior lecturer in general practice at the University of Wales College of Medicine, who is an expert in community infection, said the results were "another little bit of evidence that we are sitting on a timebomb".

Dr Butler said that both patients and doctors needed to use antibiotics sensibly. "Evidence shows that 80 per cent of antibiotics are prescribed in GP surgeries and that half of these prescriptions are unnecessary," he said.

In the UK, Dr Nielsen said, the rise in MRSA in the community was a result of faster hospital discharge, home care for cancer patients, and home kidney dialysis. GPs were also now more aware of the disease.

However, Dr Barry Cookson, of the Central Public Health Laboratory, said: "It is not a great risk to healthy people and simple hygiene procedures such as proper handwashing can keep it at bay."

In the USA, MRSA has claimed the lives of four children in the past 18 months. Two of these lived in rural American Indian communities and two were white children from big cities. None of the victims had been in contact with hospitals.

The Centre for Disease Control in Atlanta subsequently checked 112 patients with infections and found that more than half had MRSA. Only a quarter of the MRSA patients had been in hospital or long-term care.

American experts do not know how the children were infected. One theory is that the bacteria mutated into a form that can lie dormant in the community and attack vulnerable people opportunistically.

Dr Nielsen will publish his findings in the British Medical Journal in the autumn.